Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

This study is an efficiency comparison between four methods for the production of landslide susceptibility maps (LSMs), which include random forest (RF), artificial neural network (ANN), and logistic regression (LR) as the machine learning (ML) techniques and frequency ratio (FR) as a statistical method. The study area is located in the Southern Hiroshima Prefecture in western Japan, a locality known to suffer from rainfall-induced landslide disasters, the most recent one in July 2018. The landslide conditioning factors (LCFs) considered in this study are lithology, land use, altitude, slope angle, slope aspect, distance to drainage, distance to lineament, soil class, and mean annual precipitation. The rainfall LCF data comprise XRAIN (eXtended RAdar Information Network) radar records, which are novel in the task of LSM production. The accuracy of the produced LSMs was calculated with the area under the receiver operating characteristic curve (AUROC), and an automatic hyperparameter tuning and result comparison system based on AUROC scores was utilized. The calculated AUROC scores of the resulting LSMs were 0.952 for the RF method, 0.9247 for the ANN method, 0.9016 for the LR method, and 0.8424 for the FR. It is also noteworthy that the ML methods are substantially swifter and more practical than the FR method and allow for multiple and automatic experimentations with different hyperparameter settings, providing fine and accurate outcomes with the given data. The results evidence that ML techniques are more efficient when dealing with hazard assessment problems such as the one exemplified in this study. Although the conclusion that the RF method is the most accurate for LSM production as found by other authors in the literature, ML method efficiency may vary depending on the specific study area, and thus the use of an automatic multi-method LSM production system with hyperparameter tuning such as the one utilized in this study is advised. It was also found that XRAIN radar-acquired mean annual precipitation data are effective when used as an LCF in LSM production.

DOI： 10.3390/geosciences14060171

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The 2015 Nepal Earthquake (Mw7.8) affected more than 9000 schools in the country. Damage distribution in the 14 most-affected administrative districts shows that the construction practices were an important determent for the level of damage extended. The use of improper construction materials, lack of construction supervision, and non-compliance with the existing building codes during design and construction probably contributed to severe damage to most of the school buildings. Based on the damage analysis data and experience of the rebuilding process after the 2015 Nepal Earthquake, this paper highlights the steps to be considered during a rebuilding plan for school buildings after an earthquake disaster. Preliminary damage assessment results show that in the most-affected districts, about 86% of schools (locations) were affected by the earthquake and about one million students were out of their schools for a long time. The damage survey data indicate that about 30% of classrooms collapsed, about 13% of classrooms sustained major damage, and about 17% of classrooms sustained minor damage within the most-affected 14 districts. This damage report is largely based on the secondary data provided by the concerned government authorities. Such evidence of loss and damage in earthquake disasters provides an opportunity to learn lessons for future preparedness and to encounter disaster challenges. This work shares an experience on the rebuilding process of damaged schools and classrooms. It is expected that the experience reported in this paper will help in better planning of the seismic safety of school buildings in Nepal as well as in other similar seismically active regions. Most papers related to the 2015 Nepal Earthquake focus on overall building damage, but this paper addresses the issues of school buildings. As a case report, this paper probably lacks scientific originality, but the presentation of the damage data and the rebuilding process are the original work of the authors.

DOI： 10.3390/buildings14020451

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

Public response to restriction policy against the novel coronavirus disease (COVID-19) can polarize into two extremes: one absolutely in favor of restrictions for the sake of human life and health, and other absolutely against the restrictions for the sake of human rights and daily life. This study examines psychological nature of extremism regarding individuals’ self-restraint from social behavior, which was and has been encouraged by the Japanese government as restriction measures, as well as possible measures to mitigate this extremism. We hypothesize that people with more extreme views on self-restraint tend to have less knowledge of this virus, and, nevertheless, tend to be more overconfident in the sense that they falsely believe they understand COVID-19 and the effects of self-restraint. It is also postulated that overconfidence can be reduced by asking them to explain how self-restraint works. To test these hypotheses, we conducted an online experiment on the Japanese adults (n = 500) to measure the extent of their knowledge of COVID-19 and to examine the effect of explanation task on their understanding regarding COVID-19 and extremism. The results indicate that the extreme attitudes were associated with insufficient knowledge about the symptoms, risks, and characteristics of COVID-19. Moreover, their extreme attitudes tended to moderate through this experimental study to an extent that they realized they did not understand COVID-19 including the effects of self-restraint. This suggests that people with extremism may have been overconfident in their own understanding of the COVID-19 restrictions.

DOI： 10.3389/fpsyg.2024.1295807

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/geotechnics3030045

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/geosciences13080245

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：CRC Press  

DOI： 10.1201/9781003299127

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/geotechnics3030037

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Authorship：Corresponding author   Language：English   Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

Abstract

Spectral element framework for slope instability analysis includes Spectral Element Method (SEM) formulation, system requirements for serial and parallel computations, model preparation with hexahedral meshing in Cubit or Trelis, meshing and mapping technique (h- and p-refinement techniques) according to SEM, applying boundary conditions for 2D and 3D, defining inputs for material model, ground water table, seismic loading as well as processing and visualizing the results in Tecplot and ParaView. Within this framework, the safety factor in slope stability is computed and visualized with greater spectral accuracy and stability.

DOI： 10.1007/978-3-031-16898-7_11

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

Abstract

Soil material undergoes a volumetric change when deformed, and the change continues until the material reaches its critical state. In granular soils, the critical state is one that exhibits the least frictional resistance, but in clayey materials, the frictional resistance decreases further upon shearing due to particle reorientation in the plane of failure, and the material volume attains a stable or steady state only after a large amount of shear deformation, which depending on the material type varies from a few to tens of centimeters. This state of shear deformation is generally known as the residual state. This article focuses on residual-state creep shear tests on common clayey materials for the purpose of experimentally simulating the landslide creep and understanding the displacement behavior of large-scale creeping landslides. As a general understanding, the deep-seated creeping landslides displace as a result of residual-state shearing of clayey material in the slip surface. So, a modified bishop-type torsional ring shear machine was developed for studying the residual-state shear creep behavior of clayey soils. In the ring shear tests, the material is first sheared under a strain-controlled pattern, and after the sample reaches its residual state of shear, different sets of constant shear loads are applied until the sample fails again and again. The test results reveal that at the residual state of shear, the creep behavior is exhibited only after a load equivalent to the residual frictional resistance of the material is applied. Moreover, it was understood that the displacement required for the beginning of the tertiary stage of creep of particular soil material, i.e., the early stage of creep failure is the same for all sets of creep loads.

DOI： 10.1007/978-3-031-18471-0_6

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

After about six months from the 2015 Nepal Earthquake (Mw7.8, 25 April 2015), we conducted a survey to assess the level of posttraumatic stress disorder (PTSD) in disaster victims of Kathmandu Valley. Post-disaster surveys in many disaster-hit areas in the world indicate that the victims and affected people live a fearful life for certain period, so in this study we attempt to assess the state of mental health of the 2015 Nepal Earthquake victims in relatively heavy-hit areas of the Kathmandu Valley. We use a 17-item instrument for assessing PTSD containing three main types of PTSD symptoms: re-experiencing (5 items), avoidance (7 items), and hyperarousal symptoms (5 items). The survey results indicate that there was certain level of PTSD in the Kathmandu residents, and it can be associated not only with house damage and fatal loss but also the house repair work and livelihood revival. So, it is considered that delays in recovery and reconstruction may also lead to prevalence of PTSD.

DOI： 10.1016/j.ijdrr.2021.102733

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The aftershocks of the 2015 Mw7.8 Gorkha Nepal earthquake extend up to 130km to the east of the epicenter. The distribution suggests that the rupture has propagated from west to east through the Kathmandu Valley, potentially leading to more severe destruction in the valley. In addition to this, the local soil deposit influences the shaking intensity and the associated damage. The modification of the seismic wave depends on the nature of the soil deposit and the characteristics of the seismic waves, both of which are interrelated with each other in a complex manner. To evaluate the response of Kathmandu Valley sediments, the spectral element method (SEM) is employed. The models are prepared in 3D based on lithological data from the deep boreholes (i.e., 300 to 500m, up to bedrocks) in the Kathmandu Valley. The seismic response along with wavefront is produced that resembles the variational properties of sub-surface sediments along with the effects of topography and basin of Kathmandu Valley.

DOI： 10.1007/s10950-021-10029-w

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Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press Ltd.  

In this study, novel finite element approaches are proposed for numerical analysis of stress-dependent landslide movement with groundwater fluctuation by rainfall. Two new constitutive parameters that are capable of directly controlling the relationship between the apparent factor of safety and sliding velocity are incorporated into a specific material formulation used in finite element analysis for the first time. For the numerical simulation of the measured time history of the sliding displacement caused by the groundwater fluctuations, such required analytical parameters can also approximately be determined by back analysis. The proposed models are applied to a landslide field experiment on a natural slope caused by rainfall in real time in Futtsu City, Chiba Prefecture of Japan to check its applicability. The predicted and measured time histories along the horizontal direction on the upper, middle, and lower slope are compared. In addition, the deformation pattern, shear strain pattern, and possible failure mechanisms of the natural slope of such a field experiment landslide are discussed in detail based on the analysis results of the finite element method (FEM)-based numerical simulation. Moreover, the creeping landslides and possible landslide sites for further application of the proposed models are briefly discussed in the cases of Nepal and Japan as examples in Asia. It is believed that the proposed newly developed numerical models will help in understanding the secondary creep behavior of landslides triggered by extreme rainfall, and at the same time, long-term management of such landslides will be much easier in monsoon Asia. Finally, it is expected that this study will be extended for simulation of the tertiary creep behavior of landslides induced by rainfall in the near future.

DOI： 10.20965/JDR.2021.P0658

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Kathmandu Valley in Nepal is built on the soft soil deposits of lacustrine origin. The structural damage record in the valley during the past earthquakes indicates that resonance effect between the ground and structures plays an important role in intensifying the damage to the structures. Especially, in soft soil deposits, even a small-scale earthquake generates long-period shaking of the ground for comparatively long time with greater displacement. During the 2015 Gorkha earthquake in Nepal, the Kathmandu Valley ground was heavily shaken for more than 60 s with about 4 s of period, which probably was the main cause of heavy damage to multi-story tall buildings in the Kathmandu urban core. This situation of long-period ground shaking during earthquakes and heavy damage to long-period structures may happen anywhere in earthquake-prone regions of the world. So, in this study, after the 2015 Gorkha earthquake (in Nepal), we recorded microtremor and ambient vibration noise data at 33 tall building (from 7 to 19 stories) locations in the Kathmandu Valley and analyzed the recorded data for estimating predominant natural frequencies and natural periods using Floor-Spectral-Ratio technique for the buildings and Horizontal-to-Vertical Spectral Ratio technique for the ground. The results obtained by analyzing the recorded noise data for the buildings are compared with those of the corresponding nearby free-fields to explore the possibility of resonance effect. The comparison indicates that the predominant periods of about 25% tall buildings are close to the predominant periods of the corresponding grounds, and that about 35% tall buildings have almost the same predominant periods as those of the corresponding grounds. This indicates that the resonance effect is one of the major causes of the partial damage to the tall buildings in the Kathmandu Valley during the 2015 Gorkha earthquake, and hence special considerations need to be taken during design and construction of tall buildings in the Kathmandu Valley as well as in similar urban settlements.

DOI： 10.1007/s12665-021-09754-9

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Other Link： https://link.springer.com/article/10.1007/s12665-021-09754-9/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.gsd.2020.100470

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.22146/ijg.16632

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.21276/ijee.2018.11.0201

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Civil Engineers (ASCE)  

A massive landslide in the Jure village of Sindhupalchowk District, Nepal, occurred on August 2, 2014, wiping out dozens of houses and blocking the Sunkoshi River. The spectral element method (SEM) is employed here to study the stability of the slope where the landslide occurred, considering dry and wet slope conditions and pseudo-static seismic loading (with refer to 7.8Mw 2015 Barpak-Gorkha, Nepal earthquake). The results show that the Jure landslide slope becomes unsafe when the ground water table (GWT) is at the surface and peak ground acceleration (PGA) is greater than 0.2 g considering two slope cross-sections (section 2-2 and 3-3), and greater than 0.1 g for one slope cross-section (section 1-1). Based on the computational results, a correlation is made between the factor of safety (FS) and the PGA for the Jure landslide slope. Mitigation methods such as slope modification and ground water table reduction (drainage) are then proposed to increase the slope FS. The SEM results are then verified with a finite element method (FEM) technique.

DOI： 10.1061/9780784481486.010

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Japan  

Large-scale landslides are huge deep-seated failed masses that occurred in the geological past. Some of them are dormant while some are still active, creeping, and reactivating causing problems in the form of small-scale failures. Unlike small-scale failures in which the failed masses were already replaced, large-scale landslides built and modified the topography that makes it unique and differentiate from the other stable slope. In the Nepal Himalaya, large-scale landslides are widely distributed in the Lesser Himalayan and Higher Himalayan zones. But, systematic database regarding the large-scale landslide is not available. So, this paper describes a methodology to delineate large-scale landslides and preparation of the inventory map in the Himalayan terrain. Different approaches of landslide inventory mapping using GIS techniques are discussed, and validation methods are proposed.

DOI： 10.1007/978-4-431-54391-6_6

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer Japan  

Landslide occurs almost every year in Indonesia which causes tremendous damages to life and properties. Landslide hazard map would allow the identification of hazard regions for the implementation of mitigation which can minimize the loss of human life and property from future landslide occurrences. Currently, the Indonesian Government and research entities as well as academic institutions are trying to develop landslide hazard assessment model for the prone area to support prevention program, mitigation action, and evacuation plan. However, there is a lack of attention in the landslide inventory mapping as a basic input of landslide hazard mapping. Ideally, landslide inventory mapping provides detailed information about the spatiotemporal distribution of landslide occurrence. It contains the date of occurrence, types, failure mechanisms, area/volume, depth, and so on. Landslide inventory map can be prepared by several methods such as image interpretation, remote sensing techniques, detailed geomorphological fieldwork, historical archive studies, interview, and combination among several methods. The aim of this paper is to review the possibility of using various methods of inventory in Indonesia. Furthermore, this paper is also purposed to explore the use of existing landslide database for producing a landslide inventory that can be used to assess landslide hazard.

DOI： 10.1007/978-4-431-54391-6_8

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Publishing type：Research paper (scientific journal)   Publisher：GIS Landslide  

DOI： 10.1007/978-4-431-54391-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Fuji Technology Press  

Increase in number of disaster prevention experts in various fields of our society has led to greater expectations for their activities as local disaster prevention leaders. It may be of interest as well as necessary to understand what motivates people to become a disaster prevention expert. In this study, we first compare altruistic motivation levels of disaster prevention experts program attendees with those of general public for locality-based disaster mitigation plan, and then discuss appropriateness of such possibility. In addition, on the basis of the knowledge of social psychology, altruistic motivation and related awareness of both groups are also comparatively discussed.

DOI： 10.20965/jdr.2017.p0748

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1186/s40677-016-0053-x

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Language：English   Publisher：Institute of Lowland Technology, Saga University  

This paper describes the damage brought by the 2015 Nepal earthquake to urban infrastructures, modern and traditional buildings as well as some word heritage sites in and around Kathmandu city. The paper also focuses on a disaster brought to a hydropower plant by the compound action of a previous landslide and this time earthquake. Some of the possible reasons for such damage were brought to light, and challenges of the geotechnical community towards the retrofitting and recovery of the devastated structures were discussed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

This study focuses on topographic hollows, their flow direction and flow accumulation characteristics, and highlights discharge of hillslope seepage so as to understand porewater pressure development phenomena in relation with slope failure in topographic hollows. For this purpose, a small catchment in Niihama city of Shikoku Island in western Japan, with a record of seven slope failures triggered by typhoon-caused heavy rainfall on 19-20 October 2004, was selected. After extensive fieldwork and computation of hydro-mechanical parameters in unsaturated and saturated conditions through a series of laboratory experiments, seepage and slope stability modellings of these slope failures were done in GeoStudio environment using the precipitation data of 19-20 October 2004. The results of seepage modelling showed that the porewater pressure was rapid transient in silty sand, and the maximum porewater pressure measured in an area close to the base of topographic hollows was found to be higher with bigger topographic hollows. Furthermore, a threshold relationship between the topographic hollow area and maximum porewater pressure in this study indicates that a topographic hollow of 1000 sq. m area can develop maximum porewater pressure of 1.253 kPa. However, the porewater pressures required to initiate slope instability in the upper part of the topographic hollows is relatively smaller than those in the lower part of the topographic hollows.

DOI： 10.1080/19475705.2014.954150

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

In this work, we prepare and replicate a deterministic slope failure hazard model in small-scale catchments of tertiary sedimentary terrain of Niihama city in western Japan. It is generally difficult to replicate a deterministic model from one catchment to another due to lack of exactly similar geo-mechanical and hydrological parameters. To overcome this problem, discriminant function modelling was done with the deterministic slope failure hazard model and the DEM-based causal factors of slope failure, which yielded an empirical parametric relationship or a discriminant function equation. This parametric relationship was used to predict the slope failure hazard index in a total of 40 target catchments in the study area. From ROC plots, the prediction rate between 0.719-0.814 and 0.704-0.805 was obtained with inventories of September and October slope failures, respectively. This means September slope failures were better predicted than October slope failures by approximately 1%. The results show that the prediction of the slope failure hazard index is possible, even in a small catchment scale, in similar geophysical settings. Moreover, the replication of the deterministic model through discriminant function modelling was found to be successful in predicting typhoon rainfall-induced slope failures with moderate to good accuracy without any use of geo-mechanical and hydrological parameters.

DOI： 10.1080/19475705.2014.880856

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

West Java Province is the most landslide risky area in Indonesia owing to extreme geo-morphological conditions, climatic conditions and densely populated settlements with immense completed and ongoing development activities. So, a landslide susceptibility map at regional scale in this province is a fundamental tool for risk management and land-use planning. Logistic regression and Artificial Neural Network (ANN) models are the most frequently used tools for landslide susceptibility assessment, mainly because they are capable of handling the nature of landslide data. The main objective of this study is to apply logistic regression and ANN models and compare their performance for landslide susceptibility mapping in volcanic mountains of West Java Province. In addition, the model application is proposed to identify the most contributing factors to landslide events in the study area. The spatial database built in GIS platform consists of landslide inventory, four topographical parameters (slope, aspect, relief, distance to river), three geological parameters (distance to volcano crater, distance to thrust and fault, geological formation), and two anthropogenic parameters (distance to road, land use). The logistic regression model in this study revealed that slope, geological formations, distance to road and distance to volcano are the most influential factors of landslide events while, the ANN model revealed that distance to volcano crater, geological formation, distance to road, and land-use are the most important causal factors of landslides in the study area. Moreover, an evaluation of the model showed that the ANN model has a higher accuracy than the logistic regression model.

DOI： 10.1063/1.4947407

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCIENCE PRESS  

Ethiopia has a mountainous landscape which can be divided into the Northwestern and Southeastern plateaus by the Main Ethiopian Rift and Afar Depression. Debre Sina area is located in Central Ethiopia along the escarpment where landslide problem is frequent due to steep slope, complex geology, rift tectonics, heavy rainfall and seismicity. In order to tackle this problem, preparing a landslide susceptibility map is very important. For this, GIS-based frequency ratio (FR) and logistic regression (LR) models have been applied using landslide inventory and the nine landslide factors (i.e. lithology, land use, distance from river & fault, slope, aspect, elevation, curvature and annual rainfall). Database construction, weighting each factor classes or factors, preparing susceptibility map and validation were the major steps to be undertaken. Both models require a rasterized landslide inventory and landslide factor maps. The former was classified into training and validation landslides. Using FR model, weights for each factor classes were calculated and assigned so that all the weighted factor maps can be added to produce a landslide susceptibility map. In the case of LR model, the entire study area is firstly divided into landslide and non-landslide areas using the training landslides. Then, these areas are changed into landslide and non-landslide points so as to extract the FR maps of the nine landslide factors. Then a linear relationship is established between training landslides and landslide factors in SPSS. Based on this relationship, the final landslide susceptibility map is prepared using LR equation. The success-rate and prediction-rate of FR model were 74.8% and 73.5%, while in case of LR model these were 75.7% and 74.5% respectively. A close similarity in the prediction and validation rates showed that the model is acceptable. Accuracy of LR model is slightly better in predicting the landslide susceptibility of the area compared to FR model.

DOI： 10.1007/s11629-015-3464-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

This research deals with the computational accuracy impact factors of elasto-plastic spectral element applications to slope stability. It contains three categories of impact factors: 1) modelling domain related parameters, 2) spectral parameters, and 3)X elasto-plastic parameters. Each category has many accuracy impact factors. The modelling domain and elasto-plastic related impact factors can be equally applied to the elasto-plastic finite element method, however spectral corrections can only be applied for spectral element applications. This work presents a numerical evaluation of all three impact factors to the stability factor of a slope in three representative theoretical domains of slope angle, of 26.26°, 36.69°, and 45°. In addition, the study focuses on spectral element applications to slope stability evaluation, because it is a new and reliable approach in slope stability modelling. It has several benefits over the existing modelling methods to apply for slope stability modelling: 1) geometric flexibility of the finite elements, 2) high computational efficiency, 3) reliable spectral accuracy, and 4) high numerical stability.

DOI： 10.1080/17486025.2014.985337

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

This research deals with the computational accuracy impact factors of elasto-plastic spectral element applications to slope stability. It contains three categories of impact factors: 1) modelling domain related parameters, 2) spectral parameters, and 3)X elasto-plastic parameters. Each category has many accuracy impact factors. The modelling domain and elasto-plastic related impact factors can be equally applied to the elasto-plastic finite element method, however spectral corrections can only be applied for spectral element applications. This work presents a numerical evaluation of all three impact factors to the stability factor of a slope in three representative theoretical domains of slope angle, of 26.26°, 36.69°, and 45°. In addition, the study focuses on spectral element applications to slope stability evaluation, because it is a new and reliable approach in slope stability modelling. It has several benefits over the existing modelling methods to apply for slope stability modelling: 1) geometric flexibility of the finite elements, 2) high computational efficiency, 3) reliable spectral accuracy, and 4) high numerical stability.

DOI： 10.1080/17486025.2014.985337

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE GEOTECHNICAL SOC  

Nepal was hit by the M7.8 Gorkha earthquake on April 25, 2015, which was the largest earthquake in Nepal's history since 1934. The recent report presented by the Government of Nepal indicates that the recorded death toll has reached about 8800.
Following the earthquake, the Japanese Geotechnical Society (JGS), Asian Technical Committee of ISSMGE on Geotechnical Natural Hazards (ATC3), Japan Society of Civil Engineers (JSCE) and Japan Association for Earthquake Engineering (JAEE) decided to jointly dispatch a survey team to Nepal to conduct a reconnaissance survey of the major damage caused by the earthquake. This report summarizes the results of the survey of the geotechnical and structural damage in the Kathmandu valley, which were observed by the survey sub-team between May 1 and 8, 2015. Geotechnical and geological characteristics of a deep soil profile up to 600 m and a shallow profile up to 30 m are also described with the help of the database system established by Bhandary et al. (2012). In order to study the correlation between building damage ratios and the predominant period of ground vibration, a partial exhaustive type survey was conducted along NS line where microtremor measurements had been previously conducted in 2008. The predominant period of ground vibration was short at the ridge of the valley and long at its center, ranging from 1.2 to 4.5 s. A total of 532 buildings were assessed and more than 90% were classified as "No damage" or "Negligible to slight Damage" (Grade 0 and Grade 1), whereas only 5% of buildings were assessed as "Substantial to heavy damage" to "Destruction" (Grade 3 to Grade 5).
Five locations were identified where the soil had liquefied. Liquefaction-induced damage to structures at these locations was not found, except at Nepal Engineering College where minor settlement of the college building was observed. During the 1934 earthquake, foundation liquefaction was observed in Tundhikhel area, but in the 2015 earthquake no evidence of liquefaction was detected in this area.
The Kathmandu-Bhaktapur Road of Araniko Highway was heavily damaged in the Lokanthali area. The subsidence of soft soils and their lateral spreading in this area may have exacerbated the damage to this road. (C) 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sandf.2015.09.005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

This paper deals with the stability of large-scale landslides with the aim of exploring reliable safety factor in 3-dimensions (3D) for the effective implementation of landslide stability enhancement measures (LSEM) in the mountainous country like Nepal. The paper uses ‘Specfem3D_Slope’, an open-source spectral element method (SEM) based program that can effectively handle the major challenges of 3D modeling to evaluate the stability of large-scale landslides. The SEM prefers p-refinement techniques (increasing the degree of interpolation or polynomial degree or spectral degree) instead of h-refinement (refining the mesh related to elemental budgets) unlike to FEM. Then the safety factors, thus obtained seem to be reliable values as per the material properties and slope model supplied, and that can encouragingly be used in effective design and implementation of various LSEM projects. Moreover, a complete draw down effect after the LSEM gives a complete sense of the effectiveness of the measures itself. In addition, the paper emphasizes some experimental tests to know the displacement behavior of landslide’s soils (e.g., Krishnabhir landslide). A theoretical model is chosen to do some deeper exercises on 3D for the reliability of the results and later implements such criteria for ‘Laprak landslide’ of Nepal Himalaya. With this modeling method (elasto-plastic) the paper incorporates all possible instability conditions like pseudo-static earthquake loading, structural loading over the sliding mass, partially saturated ground water profile, etc., the same conditions as implemented by previous researchers for Laprak landslide. The study of two major landslides of Nepal ‘Krishnabhir landslides’ (relates to major highway) and ‘Laprak landslides’ (relates to a large number of settlements over the moving mass) reflects the major issues of large-scale landslide stability modeling of Nepal Himalaya.

DOI： 10.1007/s10706-015-9858-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Landslide susceptibility mapping is an important tool for disaster management and development activities such as planning of transportation infrastructure, settlement and agriculture. Selelkula area of the Jema River Gorge in Central Ethiopian Highland was chosen as a study area. Fuzzy logic (FL) and rock engineering system (RES) in a GIS environment were employed to prepare landslide susceptibility maps for this area. Data sets including slope, aspect, profile curvature, plan curvature, lithology, land use, distance from river and distance from lineament were generated using the field data, remote sensing and GIS. In FL, the fuzzy membership values were calculated by normalizing the frequency ratio values of each factor's class in a range between 0 and 1. Then, the fuzzy membership values were combined by fuzzy AND, fuzzy OR, fuzzy gamma, fuzzy sum and fuzzy product operators. A total of twelve landslide susceptibility maps were produced using FL and the best map was chosen based on area under the curve (AUC) of the receiver operating characteristic (ROC) curve and the highest difference between minimum and maximum susceptibility index values. Based on these criteria, the landslide susceptibility map produced using fuzzy gamma (gamma = 0.8) operator was selected. RES is a semi-quantitative method which assigns each factor's classes a value between 0 and 4 based on the principles of Hudson (Rock engineering systems, theory and practice. Ellis Horwood, Chichester, 1992) and uses an interaction matrix through a coding system of five values in previous researches but a coding system of nine values has been used in this study to provide a wider range of values for interactions among each pair of landslide factors and each landslide factor with a landslide. Unlike other methods, RES has a freedom to evaluate and assign each interaction based on expert's knowledge and experience. But it also bears the problem of subjectivity in assigning the interaction values. On the other hand, FL is completely data driven and does not show any subjectivity in assigning values for each factor class. The prediction accuracies of FL and RES, which can be determined from ROC curves, were found to be 87.2 and 88.6 %, respectively. For validation purpose, the existing landslides were overlaid over the two landslide susceptibility maps and the percentage of landslides in each susceptibility class was calculated. The percentages of landslides that fall in the high and very high susceptibility classes are slightly higher in RES than FL method and hence the former is more accurate in predicting the future landslide occurrence than the later.

DOI： 10.1007/s12665-015-4377-8

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This study was conducted to identify the influence of three principal parameters constituting topography (slope inclination, soil depth, and slope length) on hillslope instability in a small catchment, known as Higashifukubegawa of Shikoku Island, western Japan. The typhoon rainfall of 19-20 October 2004 was significant in causing a total of seven slope failures in the catchment, though other rainfall events of various intensities in the same year did not cause failure. To understand the influence of the three principal parameters, numerical modeling of seepage and slope stability was performed in slope profiles constructed by varying the three parameters across their permissible range prepared from the seven slope failures of Higashifukubegawa in GeoStudio (GeoStudio Tutorials includes student edition lessons, Geo-Slope International Ltd., Calgary, 2005 v.4). The change in porewater pressure and slope mass weight due to variation in values of principal parameters was used to interpret the change in factor of safety or instability. The results showed that (1) instability increases with increase in the values of all three selected parameters across their range in Higashifukubegawa with remarkable decreasing trend in factors of safety, (2) slope inclination and soil depth were observed to affect instability through change in both unsaturated zone moisture content and mobilizing force of slope mass, (3) but with slope length, the unsaturated zone moisture content was not found to change considerably which implies that the instability due to slope length is mainly governed by change in slope mass weight. Overall, this study has dealt in great detail with how hillslope instability changes with principal parameters of topography under the same simulating conditions of hydrological and geo-mechanical parameters.

DOI： 10.1007/s12665-014-3819-z

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Nepal is highly vulnerable to natural disasters. A high proportion of the national GDP is lost every year in landslides, floods, and many other forms of disasters. A high number of human casualties and loss of public and private property in Nepal due to natural disasters may be attributed to inadequate public awareness, lack of disaster preparedness, weak governance, lack of coordination among the concerned government agencies, inadequate financial resources, and inadequate technical knowledge for mitigating the natural disasters. In this context, quite a few awareness and training programs for disaster risk reduction (DRR) have already been initiated in Nepal and their impact assessments are also already documented. However, effectiveness of the various implemented DRR programs is not yet evaluated through an independent study.

DOI： 10.1186/s40677-014-0011-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Inderscience Enterprises Ltd.  

Statistical techniques were applied to analyse the water quality datasets of Kathmandu Basin, Nepal, to identify the major factors affecting water quality and to investigate the spatial and seasonal variations. Spatial variation was investigated using cluster analysis in which a total of 40 river monitoring sites were divided into two major clusters: low and high polluted zones. Discriminant analysis (DA), principal component analysis (PCA) and factor analysis (FA) were subjected to water quality parameters to identify the pollution sources. DA confirmed the seasonal variation of water quality data into three seasons providing 92.5% correct classification. Principal components (PCs) were extracted to distinguish the anthropogenic processes and the symmetrical correlation matrix computed with ten variables for winter, monsoon and post monsoon seasons. The significant components extracted have eigenvalues greater than 1, and account for 79%, 68% and 77% of the total variance in the winter, monsoon and post monsoon data respectively. Non-parametric tests were applied for each parameter to identify their significance differences spatially and temporally.

DOI： 10.1504/IJW.2015.070357

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Large-scale landslides in the Himalaya are defined as huge, deep-seated landslide masses that occurred in the geological past. They are widely distributed in the Nepal Himalaya. The steep topography and high local relief provide high potential for such failures, whereas the dynamic geology and adverse climatic conditions play a key role in the occurrence and reactivation of such landslides. The major geoscientific problems related with such large-scale landslides are 1) difficulties in their identification and delineation, 2) sources of small-scale failures, and 3) reactivation. Only a few scientific publications have been published concerning large-scale landslides in Nepal. In this context, the identification and quantification of large-scale landslides and their potential distribution are crucial. Therefore, this study explores the distribution of large-scale landslides in the Lesser Himalaya. It provides simple guidelines to identify large-scale landslides based on their typical characteristics and using a 3D schematic diagram. Based on the spatial distribution of landslides, geomorphological/geological parameters and logistic regression, an equation of large-scale landslide distribution is also derived. The equation is validated by applying it to another area. For the new area, the area under the receiver operating curve of the landslide distribution probability in the new area is 0.699, and a distribution probability value could explain >65% of existing landslides. Therefore, the regression equation can be applied to areas of the Lesser Himalaya of central Nepal with similar geological and geomorphological conditions. (C) 2014 Published by Elsevier B.V.

DOI： 10.1016/j.geomorph.2014.05.031

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Earthquakesare one of the most significant natural hazards in Nepal and there is a long history of destructive earthquakes in the region. Despite the risk of earthquake disasters, however, school construction practice in Nepal has largely ignored the issues of structural safety. Most schools are built without following proper design guidelines. As an effective tool to reduce earthquake disaster risk in the public schools of Nepal, the Public School Earthquake Safety Program was recently initiated in Nepal. In this program, more than 1000 public schools from six districts of Nepal were evaluated for earthquake safety, and various awareness raising and retrofitting programs were implemented. This paper describes the program features, extent of community participation, retrofitting processes and lessons learned while implementing the earthquake safety program. It also demonstrates how school earthquake safety programs ultimately increase the seismic safety of the entire community in the Himalayan regions.

DOI： 10.1080/19475705.2013.806363

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Language：English   Publisher：SPRINGER HEIDELBERG  

This paper evaluates the stability of long and steep slopes examining the effect of the critical length/depth ratio, L/H, and critical slope angle, beta(cr), by comparing the results of infinite slope equation with the spectral element method. In addition, the influence of uphill and downhill boundaries on stability of long and steep slopes is also evaluated in theoretical domains. As an example, this paper presents a stability analysis of long and steep vegetated and barren slopes in saturated and seismic conditions, and also evaluates the effectiveness of the infinite slope equation for those slopes. In the vegetated slopes, the root zone may not extend to the whole depth of slope, which may lead to overestimating the factor of safety by infinite slope equation. This paper examines the applicability of the infinite slope equation for infinitely long, steep, and shallow slope model by comparing the results of the spectral element method.

DOI： 10.1007/s11440-013-0292-x

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Because of extreme vulnerability to natural disasters, Nepal is considered a disaster hotspot in the world. For a small country with just a little less than 30-million population, the disaster statistics are always frightening. School students of Nepal are also in extreme risk of natural disasters, especially when they are in schools. In this context, a few education programmes for disaster risk reduction (DRR) have already been initiated and the results have also been already documented. However, an evaluation of the real scenario with the help of an independent research is still lacking. Therefore, this research aims to explore benefits of existing education programmes of DRR in Nepal. Altogether, 124 students from 17 districts were interviewed and various questions related to disaster information, disaster knowledge, disaster readiness, disaster awareness, disaster adaptation, and disaster risk perception were asked. Statistical analysis such as histogram analysis, distribution analysis, bivariate correlations, and independent sample t-tests were conducted to examine the relationship between students in disaster education-related programmes and the key DRR issues-related dependent variables. Findings of this independent research confirmed that initiatives taken for disaster education in Nepal are not enough and a major challenge for DRR in a school community for a country like Nepal is implementing methods, especially at the individual level. Likewise, the disaster education should not only be confined within the school students, but it must also be promoted to families and communities, which is very essential to elaborate knowledge of DRR and to contribute to a disaster safe society in the country.

DOI： 10.1080/19475705.2013.809556

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While dealing with slope stability issues, determining the state of stress and the relation between driving force and resisting force are the fundamental deterministic steps. Gravitational stresses affect geologic processes and engineering operations in slopes. Considering this fact, a concept of topo-stress evaluation is developed in this research and used to produce a shallow landslide susceptibility map in a model area. The topo-stress introduced in this research refers to the shear stress induced by the gravitational forces on the planes parallel to the ground surface. Weight of the material on a slope and friction angle of the jointed rock mass are the two fundamental parameters that are considered to govern topo-stress in this study. Considering topo-stress as a main factor for initiating shallow landslides, a GIS-based probabilistic model is developed for shallow landslide susceptibility zonation. An ideal terrain in central Nepal is selected as the study area for this purpose. Two event-based shallow landslide inventories are used to predict accuracy of the model, which is found to be more than 78 % for the first event-landslides and more than 76 % for the second event-landslides. It is evident from these prediction rates that the probabilistic topo-stress model proposed in this work is quite acceptable when regional scale shallow landslide susceptibility mapping is practiced, such as in the Himalayan rocky slopes.

DOI： 10.1007/s12665-013-2774-4

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Residual shear strength is used for design and repairs on slopes containing pre-existing shear surface. Some recent research suggested that the pre-existing shear surface of landslides can gain strength with time. In this study, torsional ring shear strength recovery tests on different soils using rest periods of up to 30 days are performed at the effective normal stress of 100 kN/m2. Test results show that recovered strength measured in the laboratory is slightly noticeable after a rest period of 3 days, but recovered strength is lost after a very small shear displacement. This paper mainly focuses on the strength recovery phenomenon from the residual-state of shear on different soils based on torsional ring shear test results and the mechanisms behind it. © 2013 Indian Geotechnical Society.

DOI： 10.1007/s40098-013-0066-2

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

Residual shear strength is generally used for design and repairs on slopes containing preexisting shear surfaces in large-scale landslides. Some recent research works suggest that the pre-existing shear surface of a large-scale landslide can regain strength with the passage of time, which should be considered in designing the slope stability measures. In this study, three landslide soils were tested in a ring shear apparatus with rest periods between shear of 1, 3, 7, 15, and 30 days, with the following main objectives (1) to understand the strength recovery behavior of landslide soils in residual state of shear after as long as 30 days of rest between shearing, (2) to understand the comparative pattern of strength recovery in highly plastic and less plastic soils, and (3) to understand the mechanism involved in strength recovery at residual state of shear. The obtained experimental results indicate that the recovery of shear strength in the residual state started to appear slightly after shear was discontinued for 3 days, and was lost immediately after a very small shear displacement. On the other hand, as understood from the experimental work in this study, the trend of strength recovery, is somewhat in increasing order with prolongation of the period that shear is discontinued.

DOI： 10.1007/978-3-319-04999-1_42

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The non-structural assessment of critical public facilities such as hospital buildings is very essential for earthquake disaster adaptation in earthquake prone regions. In Nepal, a devastating earthquake is inevitable in the long term and likely in the near future. So a non-structural earthquake vulnerability assessment study was carried out in the selected main hospitals of Nepal. This paper presents the findings of the assessment work. The results show an alarming situation and demand an immediate action in most of the hospital buildings so as to achieve a standard and acceptable level of safety. The study also recommends a gradual approach of increasing the safety level considering the socio-economic condition of the country and the fact that medium-level earthquakes are more frequent than the severe ones. Moreover, the non-structural component assessment study largely helped to convince the government officials and hospital authorities on the affordability and possibility of constructing earthquake-resistant non-structural components in the hospitals of developing countries such as Nepal, employing a slight improvement in the already employed methods of construction. © 2013 © 2013 Taylor &amp
Francis.

DOI： 10.1080/17499518.2013.805629

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Owing to fragile geo-morphology, extreme climatic conditions, and densely populated settlements and rapid development activities, West Java Province is the most landslide hazardous area in Indonesia. So, a landslide risk map for this province bears a great importance such as for land-use planning. It is however widely accepted that landslide risk analysis is often difficult because of the difficulties involved in landslide hazard assessment and estimation of consequences of future landslide events. For instance, lack of multi-temporal inventory map or records of triggering events is often a major problem in landslide hazard mapping. In this study, we propose a simple technique for converting a landslide susceptibility map into a landslide hazard map, which we have employed for landslide risk analysis in one ideally hazardous part of volcanic mountains in West Java Province. The susceptibility analysis was carried out through correlation between past landslides and eight spatial parameters related to instability, i.e. slope, aspect, relative relief, distance to river, geological units, soil type, land use and distance to road. The obtained susceptibility map was validated using cross-time technique, and was collaborated with the frequency-area statistics to respond to 'when landslide will occur' and 'how large it will be'. As for the judgment of the consequences of future landslides, expert opinion was used considering available literature and characteristic of the study area. We have only considered economic loss in terms of physical damage of buildings, roads and agricultural lands for the landslide risk analysis. From this study, we understand the following: (1) the hazard map obtained from conversion of the susceptibility map gives spatial probability and the area of an expected landslide will be greater than 500m2 in the next 2 years, (2) the landslide risk map shows that 24% of the total area is in high risk
30% in moderate risk
45% in low risk and no risk covers only 1% of the total area, and (3) the loss will be high in agricultural lands, while it will be low in the road structures and buildings. © 2013 © 2013 Taylor &amp
Francis.

DOI： 10.1080/17499518.2013.826030

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Building a reliable geo-info database and using it in various civil engineering projects as well as geo-disaster risk reduction study largely depends on the accuracy of available borehole information as well as borehole distribution density. In a developing country like Nepal, the available borehole information even in the most developed urban areas is highly sparse, which does not really help achieve the purpose of generating a geo-info database out of the available borehole information. Kathmandu Valley, the capital city area of Nepal accommodates about 3 million people in densely populated urban settlements of many poorly built and over-aged houses and buildings. It consists of thick lake deposits measuring more than 500 meters at some locations. This particular study is aimed at building a geo-info database system out of sparsely distributed borehole information, using the geo-info database in reliability check of ambient ground vibration survey results, and preparing a ground shaking map for earthquake disaster risk reduction in the Kathmandu Valley. The sparsely distributed borehole locations and different purposes of boring obviously lead to a less reliable geo-info database system. So, an extensive ambient ground vibration survey, which consists of a total of 176 survey points in about 1-km grid spacing, was conducted in Kathmandu Valley to predict the ground behavior in case of seismic shaking. The results of the geo-info database system and the ambient ground vibration survey were compared for reliability check of the latter. Finally, a ground shaking map was proposed for earthquake disaster risk mitigation in the Kathmandu Valley. The main understandings are: 1) specific use of the geo-info database system built out of the available borehole information may still be in question, but a broader implication, especially in terms of predicting the nature of soil deposit in the Kathmandu Valley can be adequately made; 2) the ground structure can be broadly predicted out of the ambient ground vibration data analysis, which in case of the Kathmandu Valley has been well confirmed by comparing the previously reported ground profiles and the results of the ambient ground vibration survey; and 3) the densely populated urban areas in the Kathmandu Valley are mostly situated over the soft and thick deposits with longer period of shaking, so longer period (i.e., 1.0-2.0 s.) structures here are prone to seismic damage.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Civil Engineers (ASCE)  

Clayey soils from a slip surface of a landslide are assumed to have already reached the residual state, necessitating a study on residual strength to understand the creeping displacement behavior of clayey soils. In this study, a creep test apparatus was developed to understand the creeping displacement behavior of typical clayey soils. The newly developed creep test apparatus is capable of measuring the displacement with respect to time under the application of a constant creep stress. The ideal creep curve for a soil material is verified in the test procedure and is found to perfect matching with obtaining results. The test results on four typical clayey soils show that the creep failure begins only when the applied shear stress (i.e., creep stress) is above the residual strength and that there is no creeping effect on or below the residual strength. This paper focuses mainly on residual-state creeping displacement behavior of typical clayey soils. Residual-state creep failure prediction curves are also proposed, which may be used to predict the failure time of creeping landslides in the future. © 2014 American Society of Civil Engineers.

DOI： 10.1061/9780784413388.028

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Civil Engineers (ASCE)  

This paper presents the effect of slow shearing rates on residual strength of three soil samples collected from the landslide areas in Nepal and Japan. The tests are performed on a torsional ring shear apparatus and the shearing rates are varied in a range of 0.073-0.586 mm/min. The effect of slow shearing rates on the residual strength of high-plasticity soils and low-plasticity soils are compared. The results showed that the shear strength from the residual state of shear was increased after the shear rate of 0.233 mm/min. The probable causes of such slightly noticeable strength from the residual state of shear are discussed. © 2014 American Society of Civil Engineers.

DOI： 10.1061/9780784413388.030

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Civil Engineers (ASCE)  

A pre-existing shear surface of a reactivated landslide was subjected to repeated sliding and recession. During the sliding, the shear strength of the shear zone was reduced to the residual state. However, the strength may be recovered from the residual state, to some extent, during a rest period. In this study, three landslide soils collected from the different large-scale landslide sites in Nepal and Japan are tested in a ring shear apparatus for the discontinued shear rest periods of 1, 3, 7, 15, and 30 days. Test results show that recovered strength measured in the laboratory is slightly noticeable after a rest period of 3 days
but, recovered strength is lost after a very small shear displacement. This paper focuses mainly on the strength recovery behavior in highly plastic and less plastic soils from the residual state of shear. The probable causes of the strength recovery are also discussed. © 2014 American Society of Civil Engineers.

DOI： 10.1061/9780784413388.026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer India  

This paper briefly discusses on spectral element method, one of the recent method applied to evaluate the stability of natural slope. The parametric study is made to prepare stability charts in 3-D for the different seismic coefficient in case of dry and fully saturated soil slope conditions. This paper utilizes common soil engineering properties under the unified soil classification system (USCS). Stability charts of some representative soil slopes along with USCS material models can be useful to analyze the stability of slopes for general purposes. This paper analyzes the stability of dry and fully saturated soil slopes with horizontal seismic pseudo-static coefficient, K h, of 0.1, and 0.2 to prepare the stability charts. It is believed that dry and fully saturated soil slope conditions are the best and worst scenario of the stability and seismic coefficient, K h, of 0.1, and 0.2 are sufficiently addressed the seismic slope instability of severe damages. The results show that the stability condition of fully saturated soil slope is equivalent to dry seismic slope instability of pseudo-static coefficient, K h, 0.2 in most of the cases. This paper employs two roots related factors: (1) root cohesion, C r, of 0-20 kN/m2
(2) root zone h r, of 2.0 m to represent the vegetated soil slope stability. A significant change in safety factor is observed as per the soil slope models as well as soil material models including root related parameters. A linear relationship of factor of safety is found with root-cohesion up to, C r, of 20 kN/m2. It may not be true for lower and higher values of root-cohesions. This paper also presents a typical numerical problem and solution to illustrate the application of design charts. © 2013 Indian Geotechnical Society.

DOI： 10.1007/s40098-013-0086-y

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Limit equilibrium method (LEM) is the most conventional and popular technique in slope stability analysis. Location of the unique failure surface and the determination of corresponding critical factor of safety (critical-FOS) of the soil slope requires a lot of trial and research. With this amount of trial and research results, we evaluate the field of factor of safety (FOS-field), which represents the critical-FOS at a point within the domain of all possible failure surfaces. Such a field can be very important for the precise judgment of the most critical-FOS of the slope and its perturbation. This paper also presents the evaluation of the FOS-field of vegetated slopes, thus providing an analytical way to examine the effect of vegetation on the soil slope stability. We evaluated the stability of vegetated and barren soil slopes under dry and fully saturated conditions. With dry and fully saturated conditions, the behaviour of slopes in most favourable and worst conditions can be simulated. Evaluation of FOS-field for various slope geometries and conditions show that the more unstable the slope becomes, the more difficult it will be to pinpoint the location of the critical failure surface with the unique least FOS. We verified the LEM codes with finite element method (FEM) and spectral element method (SEM) codes considering a sample problem from Smith and Griffiths' book (Smith and Griffiths 2003). © 2013 Taylor &amp
Francis.

DOI： 10.1080/17486025.2012.744101

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Few researchers have studied the creeping displacement behavior of clayey soils using a triaxial compression cell and oedometer
however, in most cases, they have concentrated on the pre-peak state of shear. Clayey soil from a landslide is assumed to have already reached the residual-state, necessitating a study on residual strength to understand the creeping displacement behavior of clayey soils from landslides. In this work, an existing torsional ring shear apparatus was modified to understand the creeping displacement behaviors of typical clayey soil. The newly developed creep test apparatus is capable of measuring the displacement with respect to time under the application of a constant creep stress. This paper focuses mainly on residual-state creep behaviors of typical clayey soils. Residual-state creep failure prediction curves are also proposed, which may be used to predict failure time and displacement of creeping landslides in the future. © 2013 Springer Science+Business Media Dordrecht.

DOI： 10.1007/s11069-013-0799-3

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Residual shear strength is generally considered in the design of preventive measures for slopes consisting of preexisting shear surfaces of large-scale landslides. Recent research suggests that the preexisting shear surface of a reactivated landslide can regain strength with the passage of time, which might also be considered in designing the slope stability measures. In this study, three reactivated landslide soils were tested in a ring shear apparatus for the discontinued shear periods of 1, 3, 7, 15, and 30. days with the following main objectives: (i) to understand the strength recovery behavior of landslide soils in a residual state of shear after as long as 30. days of discontinued shear, (ii) to understand the comparative pattern of strength recovery in highly plastic and less plastic soils, and (iii) to understand the mechanism involved in strength recovery at a residual state of shear. The results indicate that recovered strength measured in the laboratory is hardly noticeable after a rest period of 3. days, but recovered strength is lost after a small shear displacement. This paper primarily focuses on the effect of strength recovery from residual strength on preexisting shear surface soils and the mechanisms behind it. © 2013 Elsevier Ltd.

DOI： 10.1016/j.jseaes.2013.08.023

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Situated over the Himalayan tectonic zone, Kathmandu Valley as a lake in geological past has a long history of destructive earthquakes. In recent years, the earthquake risk of the valley has significantly increased due mainly to uncontrolled development, poor construction practices with no earthquake safety consideration, and lack of awareness among the general public and government authorities. Implementation of land use plan and building codes, strengthening of design and construction regulations, relocation of communities in risky areas, and conduction of public awareness programs are suitable means of earthquake disaster risk management practice. Kathmandu, the capital of Nepal, is still lacking earthquake disaster risk management plans. So, this paper highlights some initiatives adopted by both governmental and nongovernmental organizations of Nepal to manage earthquake disaster risk in the Kathmandu Valley. It provides some comprehensive information on recent initiatives of earthquake disaster risk management in the valley and also highlights the outcomes and challenges.

DOI： 10.1007/s11069-013-0732-9

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Landslide susceptibility assessment is a major research topic in geo-disaster management. In recent days, various landslide susceptibility and landslide hazard assessment methodologies have been introduced with diverse thoughts of assessment and validation method. Fundamentally, in landslide susceptibility zonation mapping, the susceptibility predictions are generally made in terms of likelihoods and probabilities. An overview of landslide susceptibility zoning practices in the last few years reveals that susceptibility maps have been prepared to have different accuracies and reliabilities. To address this issue, the work in this paper focuses on extreme event-based landslide susceptibility zonation mapping and its evaluation. An ideal terrain of northern Shikoku, Japan, was selected in this study for modeling and event-based landslide susceptibility mapping. Both bivariate and multivariate approaches were considered for the zonation mapping. Two event-based landslide databases were used for the susceptibility analysis, while a relatively new third event landslide database was used in validation. Different event-based susceptibility zonation maps were merged and rectified to prepare a final susceptibility zonation map, which was found to have an accuracy of more than 77 %. The multivariate approach was ascertained to yield a better prediction rate. From this study, it is understood that rectification of susceptibility zonation map is appropriate and reliable when multiple event-based landslide database is available for the same area. The analytical results lead to a significant understanding of improvement in bivariate and multivariate approaches as well as the success rate and prediction rate of the susceptibility maps.

DOI： 10.1007/s11069-013-0715-x

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The change in shearing rate due to the earthquake or volcanic activities may be affected the residual strength of slip surface materials of reactive landslide or creeping landslide. Few studies have been performed to address the effectof shearing rate on residual strength. However, the rate effect mechanism on residual strength has not been clarified yet. In this study, effect on the residual strength of kaolin clay due to the change in shearing rate is investigated using a torsional ring shear apparatus. The shearing rate in the ring shear tests are varied in a range of 0.073 to 0.586 mm/min. Test results show that hardly increase in residual strength with increase in shearing rate of a kaolin clay. © 2013, EJGE.

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High-order finite element method (FEM) formulation also referred to as spectral element method (SEM) formulation is currently implemented in this paper for 3-dimensional (3-D) elasto-plastic problems in stability assessment of large- scale slopes (vegetated and barren slopes) in different instability conditions such as seismic and saturation. We have reviewed the SEM formulation, and have sought its applicability for vegetated slopes. Utilizing p (high-order polynomial degree or spectral degrees) and h (mesh operation for quality meshing in required elemental budgets) refining techniques in the existing FEM, the complexity of problem domain can be well addressed in greater numerical stability. Unlike the existing FEM formulation, this high-order FEM employs the same integration and interpolation points to achieve a progressive response of the instability, which drastically reduces the computational costs (formation of diagonalized mass matrix) and offers significant benefits to slope instability computations for serial and parallel implementations. With this formulation, we have achieved the following three qualities in slope instability modeling: 1) geometric flexibility of the finite elements, 2) high computational efficiency, and 3) reliable spectral accuracy. A sample problem has also been presented in this paper, which has accommodated all aforesaid numerical qualities.

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The Himalayan mountains and their surroundings are hit by a major earthquake in 100-year or less interval. A study conducted in 2002 revealed that Kathmandu valley of Nepal will suffer a great damage if an M8.0 class earthquake hits the region again. In this study, we conduct an ambient ground vibration survey in the valley, which has a thick lacustrine lake deposit, and analyze the recorded data so as to prepare a seismic damage risk map based on the natural periods of the ground. A portable velocity sensor was used in the survey at 172 locations covering the valley core. Fourier analysis of each recorded dataset yielded natural periods of the surveyed ground points, which were then interpreted in terms of the seismic damage risk map.

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This paper mainly focuses on current numerical implementations in slope instability computations. We successfully implemented two simplified numerical procedures in one sample problem referring from Smith and Griffiths’ book entitled “Programming the finite element method, third edition, John Wiley and Sons, New York, 2003”, that was originally solved by the finite element method (FEM). This paper briefly describes the implemented numerical procedures, their scopes and limitations. Result shows that the SEM based procedure is found to be more effective to handle simple to complex problem of small to large-scale problem domain due to its effective computational capacity as well as a higher degree of work accuracy. For this, newly released open source programs SPECFEM3D_GEOTECH [3] along with FEM program [10] have been used.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ICE PUBLISHING  

A new numerical scheme in the finite-element method was used to simulate both the progressive nature of failure and the interaction of the soil-root matrix continuum under dry and fully saturated conditions. Computations suggested that a certain range of root area ratio (the effective RAR range, or ERAR range) should be identified for a given slope geometry, vegetation type and maturity period. The ERAR range represents all the RARs that impart a factor of safety (FOS) greater than or equal to a particular FOS (the benchmark FOS). The benchmark BMFOS is the anticipated FOS, depending on factors such as demographic distribution and proximity to utilities. Beyond the ERAR range, vegetation does not impart stability to the slope. Theoretically, higher ranges of RAR beyond the ERAR range (the ineffective RAR range) can cause slope failure. This new numerical scheme evaluates the root-reinforcement effect on slope stability. This information is useful for analysing, designing and implementing soil-bioengineering slopes.

DOI： 10.1680/geot.11.P.039

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Beijing Normal University Press  

Some of the buildings in Aceh Province, Indonesia constructed after the 2004 earthquake and tsunami disaster were found vulnerable. The vulnerable buildings were retrofitted to make them safer and child friendly. Save the Children, one of the implementing agencies, assumed that the process of retrofitting would attract interest from the communities, raise their earthquake awareness, stimulate earthquake safe construction practices, and contribute to earthquake disaster risk reduction. It was also assumed that the retrofitting process would benefit the communities through knowledge transfer of safer construction practices. To assess the impact on awareness and knowledge transfer of the retrofitting work carried out by Save the Children from 2005 to 2008, a survey was carried out in 2009. A total of 104 people who were directly involved in the retrofitting/rehabilitation process were interviewed. The survey covered four districts in Aceh Province, Indonesia where schools, health facilities, and houses were retrofitted. The survey results show that the respondents felt that the impact of retrofitting work on transferring knowledge in the communities was not significant. However, the respondents felt that the retrofitting work had a definite impact on raising awareness of disaster risks and measures for disaster risk reduction.

DOI： 10.1007/s13753-013-0019-5

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Kathmandu Valley, an intermontane basin of the Himalaya, has experienced many destructive earthquakes in the past The observations of the damage pattern during the 1934 Earthquake (M-W = 8.1), in particular, suggest that the spectral ground amplification due to fluvio-lacustrine sediments plays a major role in intensifying the ground motion in the basin. It is, therefore, imperative to conduct a detailed study about the floor variation of sediments in the basin. In this paper, a preliminary attempt was made to estimate the thickness of soft sediment in the Kathmandu Basin using microtremor observations. The measurements of microtremors were carried out at 172 sites spaced at a grid interval of I km. The results showed that the predominant frequency varies from 0.488 Hz to 8.9 Hz. A non-linear regression relationship between resonance frequency and sediment depth was proposed for the Kathmandu Basin. The thickness of lacustrine sediments at various points in the basin was estimated using the proposed equation, and then the estimated thickness was used to plot a digital elevation model of the basement topography and cross profiles of the sediment distribution in the basin. The results were validated by correlating the estimated sediment thickness with geology and geomorphology of the study area. (c) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2012.11.011

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Language：English   Publishing type：Research paper (international conference proceedings)  

The paper presents finite element (FE) modelling and simulation of a newly developed rockfall protective cable-net structure in Japan, named the Long-span Pocket-type Rocknet (LPR). A reference case LPR was taken and its element-level laboratory tests and structure-level full-scale field tests conducted in the past were utilized for the calibration and verification of the numerical model exercised on the platform of the code LS-DYNA. The ultimate goal of this research is to shade lights to the targeted design guideline of LPRs. Therefore, deliberately, a simplified (equivalent) but yet rigorous approach has been adopted without going into interface-level detailing. Moreover, a number of confusions unaddressed by the state-of-the-art literatures regarding the effects of the changes in various impact load characteristic-parameters resulting into the same specified kinetic energy have been investigated using the FE model. Furthermore, an investigation on the performance of the existing energy dissipator installed in LPR and the scope of its future modification is discussed. © Springer-Verlag Berlin Heidelberg 2013.

DOI： 10.1007/978-3-642-31319-6-76

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Berlin Heidelberg  

Geologically young and tectonically active Himalayan Range is characterized by highly elevated mountains and deep river valleys. The mountainous terrains of Nepal Himalaya are characterized by dynamic physical processes, and therefore, mitigation of geo-disaster is a big challenge. A better understanding of the geological nature of the terrain and the interaction of various triggering factors of geo-disaster will greatly help in the development of safer infrastructures, mitigation of geo-disaster, and control of land degradation in the Himalaya. Over the years, Nepal has gained a significant amount of experiences in geo-disaster studies, especially in design and survey of geo-disaster mitigation programs, in the fields of hazard and risk assessment, in low cost rural road engineering
in community based river training work and in slope maintenance incorporating indigenous techniques. This chapter provides an overview of geo-disasters in Nepal and their mitigation efforts. In this chapter, all geological zones of Nepal are evaluated from the perspective of geo-disaster occurrences. Geo-disaster mitigation efforts of both governmental and non-governmental sectors are also evaluated. People’s perception for geo-disaster mitigations efforts are also discussed in this chapter.

DOI： 10.1007/978-3-642-29107-4_6

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Landslides are the most frequent natural disaster in Nepal. As such, the scientific study of the Nepal landslides has been in progress for several years, but no significant achievement has been made in preventing landslides and mitigating disaster damage yet. As one important aspect of dealing with landslides is understanding their distribution pattern based on geological and geomorphological formations, this paper addresses these issues, and attempts to present a scenario of large-scale landslide distribution along the road corridors of major highways in central Nepal. As a result of landslide mapping using aerial photographs, topographical maps and field verification, the following points were understood: (1) the distribution of large-scale landslides is relatively dense over the area close to tectonic thrusts
(2) slate and phyllite zones have a greater ratio of landslide distribution
and (3) topographies with a mean slope angle of about 27-36 degrees have denser distribution of large-scale landslides. © 2013 Copyright Taylor and Francis Group, LLC.

DOI： 10.1080/17499518.2012.743377

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Past researchers have anticipated the occurrence of a great earthquake in the central Himalayas in the near future. This may cause serious damage in the Kathmandu Valley, which sits on an ancient lake bed zone, with lacustrine sediments of more than 500 m depth. In this study, the predominant frequency of ground motion is evaluated using the Horizontal-to-Vertical {H/V) spectral ratio technique and recordings of ambient noise. The results of the H/V ratio show two peaks in about 20 percent of the locations, which are distributed mainly in and around the center and northern part of the Kathmandu Valley. The predominant frequencies vary from 0.5 Hz to 8.9 Hz in the study area, whereas the second resonance frequency varies from 4 Hz to 6 Hz in the center and northern part of the valley. This indicates that the center and northern part of the valley have a wide range of resonance frequency due to two levels of impedance contrast - one may be from the surface layer and the other may be from the layer underneath. These two levels of resonance indicate the importance of considering the effects of surface and lower layers during the planning and designing of infrastructures in the Kathmandu Valley.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Books

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10421241

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Past researchers have anticipated the occurrence of a great earthquake in the central Himalayas in the near future. This may cause serious damage in the Kathmandu Valley, which sits on an ancient lake bed zone, with lacustrine sediments of more than 500 m depth. In this study, the predominant frequency of ground motion is evaluated using the Horizontal-to-Vertical (H/V) spectral ratio technique and recordings of ambient noise. The results of the H/V ratio show two peaks in about 20 percent of the locations, which are distributed mainly in and around the center and northern part of the Kathmandu Valley. The predominant frequencies vary from 0.5 Hz to 8.9 Hz in the study area, whereas the second resonance frequency varies from 4 Hz to 6 Hz in the center and northern part of the valley. This indicates that the center and northern part of the valley have a wide range of resonance frequency due to two levels of impedance contrast - one may be from the surface layer and the other may be from the layer underneath. These two levels of resonance indicate the importance of considering the effects of surface and lower layers during the planning and designing of infrastructures in the Kathmandu Valley.

DOI： 10.1007/s11803-012-0115-3

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Purpose: As the widely held perception is that retrofitting is a complicated process and is expensive, the purpose of this paper is to analyze cost effectiveness of retrofitting existing buildings in order to make them safer against earthquake and also to add child friendly features. This case study focuses on the simple method of retrofitting on rectangular single storey existing school buildings. The school buildings are of different types, based on material, shape and size, number of storeys and their vulnerability to earthquake is different case by case. The paper also outlines the process of vulnerability assessment and approach to retrofitting. Design/methodology/approach: The paper is based on the data collected from a case study carried out in Aceh (Indonesia) as a part of an assessment of vulnerability of newly constructed school facilities and retrofitting them in order to increase their seismic performance. Findings: One of the key findings of this study is that retrofitting can be achieved through the use of simple methods, tools and equipment and local human resource. This approach not only reduced the vulnerability of school children to earthquake disaster but also contributed to disseminate the message of culture of safety among the neighboring communities. Another major finding is that cost of retrofitting is less compared to the cost of demolition and rebuilding. The retrofitting option further saves the cost as it is time saving and the downtime is less. The retrofitting process and onsite training can also be an effective medium for dissemination of best construction practices in the community. The process also helps the local people to understand the context of risk and raise awareness on disaster risk reduction. Research limitations/implications: The findings of this paper are not limited to vulnerability assessment and retrofitting of school building in Aceh. They can be replicated in other parts of Indonesia and countries having similar type of buildings. Practical implications: The findings of this paper will be useful for decision makers to replicate similar processes in other types of schools in other areas. The findings will also be useful advocate disaster safer and child friendly schools. Originality/value: The paper is unique in its findings that retrofitting of school buildings does not only make the schools safer and reduces the risk to children but is also cost effective compared to new construction. © Emerald Group Publishing Limited.

DOI： 10.1108/17595901211201132

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Language：English   Publishing type：Research paper (international conference proceedings)  

New numerical scheme in finite element method (FEM) is used to simulate both the progressive nature of failure and interaction of the soil-root matrix continuum. Computations suggest that a certain range of Root area ratio (effective RAR-range, i.e. ERAR-range) should be identified for the given slope geometry, vegetation type and maturity period. The ERAR-range represents all the RARs which impart a factor of safety (FOS) greater or equal to a particular FOS (benchmark FOS, i.e. BMFOS), BMFOS being the anticipated FOS depending on various factors (demographic distribution, proximity to utilities etc.). Beyond the ERAR-range vegetation does not impart to the stability of the slope. Theoretically, higher range of RAR beyond the ERAR-range (ineffective RAR-range, i.e. IERAR-range) even causes the slope failure. Hence, the simulation can be useful tool for the effective evaluation of vegetation effect on slope stability modeling. © 2012 American Society of Civil Engineers.

DOI： 10.1061/9780784412121.059

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

In a previous companion paper, we presented a three-tier modelling of a particular type of rockfall protective cable-net structure (barrier), developed newly in Japan. Therein, we developed a three-dimensional, Finite Element based, nonlinear numerical model having been calibrated/back-calculated and verified with the element- and structure-level physical tests. Moreover, using a very simple, lumped-mass, single-degree-of-freedom, equivalently linear analytical model, a global-displacement-predictive correlation was devised by modifying the basic equation - obtained by combining the principles of conservation of linear momentum and energy - based on the back-analysis of the tests on the numerical model. In this paper, we use the developed models to explore the performance enhancement potential of the structure in terms of (a) the control of global displacement - possibly the major performance criterion for the proposed structure owing to a narrow space available in the targeted site, and (b) the increase in energy dissipation by the existing U-bolt-type Friction-brake Devices - which are identified to have performed weakly when integrated into the structure. A set of parametric investigations have revealed correlations to achieve the first objective in terms of the structure's mass, particularly by manipulating the wire-net's characteristics, and has additionally disclosed the effects of the impacting-block's parameters. Towards achieving the second objective, another set of parametric investigations have led to a proposal of a few innovative improvements in the constitutive behaviour (model) of the studied brake device (dissipator), in addition to an important recommendation of careful handling of the device based on the identified potential flaw.

DOI： 10.5194/nhess-12-1135-2012

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Language：English   Publishing type：Research paper (scientific journal)  

Study of large-scale landslides in Nepal has been largely descriptive and qualitative and limited to site specific cases. This paper describes some preliminary efforts focusing on the understanding of large-scale landslides, their processes and mechanisms that contribute to instability and catastrophic failure in a regional scale. It also reports the use of geographical information system (GIS) database, compiled primarily from aerial photographs and field visits, to describe the physical characteristics of landslides and the statistical correlations between landslide frequency and terrain variables in the Lesser Himalayan Zone of central Nepal. To this end, large-scale landslide database covering a regional area of the Lesser Himalayan Zone is prepared and discussed in terms of their geological and topographical controls with morphometric characteristics.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Landslide hazard assessment is a primary tool to understand the basic characteristics of slopes that are prone to landslides, especially during extreme rainfall. In this study, weights-of-evidence modelling a bivariate statistical method, and a logistic regression model, a multivariate statistical method, were used for landslide hazard mapping in two catchments of the Siwaliks in the Nepal Himalaya. Two typical catchments, Charnath and Jalad of the Siwaliks in eastern Nepal, were selected for the landslide hazard mapping. Both modelling approaches were applied by considering 10 intrinsic factors and one extrinsic factor. Mainly digital elevation model-based causative factors and field data were used to prepare data layers of landslide causative factors. In many approaches for modelling of landslide hazard in GIS, the model validation process is always dependent, and landslide data, which are used to calculate a landslide hazard index (LHI), are applied for verification. However, in this study, the LHI was calculated in one catchment (Jalad) and the same index for a different class of causative factors was applied for another catchment (Charnath), and the LHI was verified. The verification results were very promising, with an independent prediction rate of about 75%. This validates weights-of-evidence and logistic regression models for landslide hazard assessment in the Siwaliks Range of Nepal.

DOI： 10.1080/19475705.2011.629007

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Many researchers have studied creeping behaviour of clayey soils in the laboratory using both oedometer and triaxial tests
however in most cases, they have only concentrated on the pre-peak creep behaviour of soil, which does not adequately explain the creep movement that undergo large displacements at close-to-residual state of shear. This necessitates the importance of further studying creep behaviour of clayey soils in residual-state of shear. In order to investigate creep behaviour of clayey soils, a new concept of residual-state creep test in a modified torsional ring shear machine is developed in laboratory, which can simulate the creeping displacement behaviour of clayey soils. Representative clayey soils, which have higher percentage of Smectite, Chlorite, Mica and commercially available Kaolin clay, are taken in this study. A series of residual-state creep test (i.e. seven tests) with varying applied constant shear stress for each sample were conducted, the results thus obtained are interpreted in terms of Residual-State Creep Stress Ratio (RCSR), at which the soil samples fail at their residual-state of shear. The term RCSR is the ratio of applied constant shear stress with residual strength. The test results show that when RCSR ≤1, the clayey soil does not show creeping behavior where as the soil undergo creeping behavior when RCSR&gt
1. This paper mainly focus on the methods of residual-state creep test, its implications for the study of creeping displacement behavior of clayey soils. © 2012 American Society of Civil Engineers.

DOI： 10.1061/9780784412121.071

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The Kathmandu Valley with an estimated current urban population of 5 million has been shaken many times in the past by damaging earthquakes. The valley was formerly a lake and although it is clear that much of the historical damage in the valley arose from seismic amplification associated with thick lake sediments, which in places exceed 500 m, few studies have been undertaken to understand the variability of seismic site response throughout the valley. In this study, we map the spatial variability of the dominant period of amplification using a horizontal-to-vertical spectral ratio technique derived from recordings of ambient noise. The resulting map is a first step towards seismic microzonation. We find that the area near the center of the valley, corresponding to the thickest sedimentary deposits, is associated with dominant periods that approach 2 s. Long-period shaking during future earthquakes is expected to be especially severe in this part of the valley since it corresponds to the urban center where numerous tall structures and long-span bridges with relatively long natural periods are to be found.

DOI： 10.1080/13632469.2012.693242

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Landslide mass are supposed to reach residual-state which naturally demands residual-state creep study. To study the creep behavior of landslide soils, a method for residual-state creep test with a modified torsional ring shear machine was developed in laboratory, which can simulate the creeping landslide phenomena. To understand the creeping behavior of landslide soils, three representative landslide soil samples, which have higher percentage of Smectite, Chlorite, and Mica, are taken in this study. A series of residual-state creep test (i.e. seven tests) with varying applied constant shear stress for each sample were conducted, the results thus obtained are interpreted in terms of Residual-State Creep Stress Ratio (RCSR), at which the soil samples fail at their residual-state. The term RCSR is the ratio of applied constant shear stress with residual strength. The test results show that when RCSR ≤1, the soil does not show creeping behavior where as the soil undergo creeping behavior when RCSR > 1.This paper mainly focus on the methods of residual-state creep test, its implications for the study of creeping displacement behavior, and further possibilities of creeping displacement prediction based on experimental findings. © 2011, International Journal of GEOMATE.

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Other Link： http://geomatejournal.com/articles/2011/1/1

Language：Japanese   Publisher：Japan Society of Civil Engineers  

Understanding current environmental condition is one of the most important issues for achieving effective policy for not only environmental protection but also disaster prevention. Element distribution in the water environment at Kathmandu area was investigated in this study in order to understand current environmental conditions in the areas. The characteristic elements observed in this area were considered to be Cu and Sr, the concentrations of which seem to be relatively higher than those in the other Asian areas. Water contamination problem in that area was also serious, and urgent and effective countermeasures are required. These were caused mainly by organic substances, therefore infrastructures for environmental protection such as sewage treatment plant and waste treatment facility should be prepared and operated sufficiently. Besides, water quality monitoring system also should be developed for environmental protection and for future application of water quality information to disaster countermeasures.

DOI： 10.2208/jscejhe.67.I_1309

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

An innovative configuration of pocket-type rockfall protective cable-net structure, known as Long-span Pocket-type Rock-net (LPR), has been developed in Japan. The global performance of the proposed system was initially checked by the experimental (full-scale) modelling. Given the various limitations of the physical experiments, particularly for the parametric study to have a detailed understanding of the newly developed system, a reliable and simplified method of numerical modelling is felt necessary. Again, given the sophistication involved with the method of numerical simulation, a yet simplified modelling approach may prove more effective. On top of this background, this paper presents a three-tier modelling of a design of LPR. After physical modelling, which has revealed that the displacement response may be taken more vital for LPR performance, Finite Element based numerical modelling is presented. The programme LS-DYNA is used and the models are calibrated and verified with the element-and structure-level experiments. Finally, a simple analytical modelling consisting of the equivalently linear and elastic, lumped-mass, single-degree-of-freedom system, capable of predicting the global displacement response, is proposed based on the basic principles of conservation of linear momentum and energy. The model is back-calculated and modified from the analyses of the verified numerical model.

DOI： 10.5194/nhess-11-3197-2011

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A new numerical scheme in Finite Element Method (FEM) along with Mesh Free Method (MFM) and suitable convergence criterion is used to simulate the progressive nature of failure in soil-root matrix continuum. With the consideration of homogenizing approach, the complex behavior of soil-root interaction can reliably be captured of any natural slopes. Root-reinforcement effect has significant role in modifying stress anisotropy and displacement behavior of the slope. Result shows that stability factor first increases with RAR, after attaining certain stability factor further increment of RAR within certain limit does not impart on stability factor of slopes. After certain RAR say more than 0.5%, there is no any change on stability factor. Results show that vegetation has significant influences on safety factor in certain effective RAR-range, which further illustrates the necessities of vegetation cover in slopes; however, it requires more realistic model parameters and boundary conditions to perform simulations that are more relevant. © 2011, International Journal of GEOMATE.

DOI： 10.21660/2011.1i

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Landslides, primarily occurring in deep-seated landslide areas, frequently damage important roads in Nepal and contribute to massive economic losses and public suffering every year. Efforts to understand these landslides, which are often only regarded as geological phenomena, through material shear behaviour however remain insignificantly reported. In order to narrow this research gap, this paper first addresses spatial distribution of these landslides in about 150-km arterial road corridors in central Nepal, and then discusses their occurrence mechanism in terms of a relation between material shear strength and mineralogical composition. The deep-seated landslide inventory prepared out of the aerial photos and topo-sheets revealed that the landslide distribution is dominant in phyllitic and slate zones of geology while the laboratory tests on clay materials, sampled from 15 locations in the study area, in ring shear machine and x-ray diffractometer exhibited that the landslide soils, especially from the phyllitic area, possess comparatively high angle of shear resistance in a range of 20-30 degrees with remarkable influence of mica and chlorite composition, whose increased relative amount was found to result in notable decrease of the angle of shear resistance. © 2011 ASCE.

DOI： 10.1061/41165(397)173

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society on Water Environment  

Matsuyama region, located in Shikoku Island, Japan faces the Seto Inland Sea on the west, where the annual rainfall is relatively less than in the other areas in Japan. In such favorable condition, the cultivation of citrus fruits is popular, and there are a large number of small reservoirs for irrigation purposes. The citrus groves are distributed in hilly areas surrounding the paddy fields and residential areas so there are higher chances for the nearby water environment to get affected by leachate from the groves. This paper investigates the water quality characteristics of the leachate from the groves, and studies the changes of the leachate quality near the collecting reservoirs. It was found that the grove soils are highly acidic and the leachate contains metals and nutrients in high concentration. On the other hand, the water quality of the leachate changed after it flowed into the reservoirs, and the concentrations became lower. It is understood that chemical and biological reactions help remove the contaminants in the reservoir, and from the standpoint of self-purification, reservoirs play an important role. This paper also discusses the kinetics of the self-purification and the quantitative estimation based on the experimental results.

DOI： 10.2965/jwet.2011.111

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Construction of roads in the mountains of Nepal is quite complicated because of steep slopes, thick soil profiles, weak rockmass and the extreme rainfall of the monsoon season. In the name of “low cost”, many roads of Nepal do not have any standard engineering structures. As a result, low cost road construction and maintenance programs are widely affected by landslide and debris flow triggered by monsoon rainfall. Generally, shallow failure occurred along the roadside, both in uphill as well as downhill slopes, are major geological problems of roads of Nepal. Although, cost effective techniques are very important for a developing country like Nepal, experience of Nepal reveals that low cost roads are not the best solution for sustainable development of underdeveloped countries.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Roadside slope failures often result in day to week-long traffic disruption and are a major problem in Nepal so that timely maintenance of roadside slopes needs greater priority for smooth operation of traffic. In this paper, we develop a Geographic Information Systems (GIS)-based maintenance model considering pavement and roadside slope stability conditions. A pavement maintenance priority map is prepared based on pavement condition. International Roughness Index (IRI) is used as the pavement condition index. Similarly, a roadside slope maintenance priority map is produced by analyzing slope stability condition. An integrated maintenance priority map is produced by combining both pavement and roadside slope maintenance priority maps with consideration of weighting of each maintenance component. The integrated maintenance priority index developed in the research lies from 1 to 3. and is distributed heterogeneously. Higher index values qualify for higher priority in maintenance planning. Thus, a conventional method of maintenance planning under the constraints of budget, time and resources can be improved by incorporating the actual condition of pavement and roadside slope failure susceptibility, which has the potential to improve significantly the serviceability of the road system. The study shows that GIS, which can manage and visualize different types of data together or separately, can help the decision making process for road maintenance planning in the Himalayan regions. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtrangeo.2009.06.016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Roadside slope failures often result in day to week-long traffic disruption and are a major problem in Nepal so that timely maintenance of roadside slopes needs greater priority for smooth operation of traffic. In this paper, we develop a Geographic Information Systems (GIS)-based maintenance model considering pavement and roadside slope stability conditions. A pavement maintenance priority map is prepared based on pavement condition. International Roughness Index (IRI) is used as the pavement condition index. Similarly, a roadside slope maintenance priority map is produced by analyzing slope stability condition. An integrated maintenance priority map is produced by combining both pavement and roadside slope maintenance priority maps with consideration of weighting of each maintenance component. The integrated maintenance priority index developed in the research lies from 1 to 3. and is distributed heterogeneously. Higher index values qualify for higher priority in maintenance planning. Thus, a conventional method of maintenance planning under the constraints of budget, time and resources can be improved by incorporating the actual condition of pavement and roadside slope failure susceptibility, which has the potential to improve significantly the serviceability of the road system. The study shows that GIS, which can manage and visualize different types of data together or separately, can help the decision making process for road maintenance planning in the Himalayan regions. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jtrangeo.2009.06.016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In the Himalaya, people live in widely spread settlements and suffer more from landslides than from any other type of natural disaster. The intense summer monsoons are the main factor in triggering landslides. However, the relations between landslides and slope hydrology have not been a focal topic in Himalayan landslide research. This paper deals with the contributing parameters for the rainfall-triggered landslides which occurred during an extreme monsoon rainfall event on 23 July 2002, in the south-western hills of Kathmandu valley, in the Lesser Himalaya, Nepal. Parameters such as bedrock geology, geomorphology, geotechnical properties of soil, and clay mineralogy are described in this paper. Landslide modeling was performed in SEEP/W and SLOPE/W to understand the relationship of pore water pressure variations in soil layers and to determine the spatial variation of landslide occurrence. Soil characteristics, low angle of internal friction of fines in soil, medium range of soil permeability, presence of clay minerals in soil, bedrock hydrogeology, and human intervention were found to be the main contributing parameters for slope failures in the region.

DOI： 10.1007/s00254-008-1531-6

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Geologically and tectonically active Himalayan Range is characterized by highly elevated mountains and deep river valleys. Because of steep mountain slopes, and dynamic geological conditions, large-scale landslides are very common in Lesser and Higher Himalayan zones of Nepal Himalaya. Slopes along the major highways of central Nepal namely Prithvi Highway, Narayangadh-Mugling Road and Tribhuvan Highway are considered in this study of large-scale landslides. Geologically, the highways in consideration pass through crushed and jointed Kathmandu Nappe affected by numerous faults and folds. The relict large-scale landslides have been contributing to debris flows and slides along the highways. Most of the slope failures are mainly bechanced in geological formations consisting phyllite, schist and gneiss. Laboratory test on the soil samples collected from the failure zones and field investigation suggested significant hydrothermal alteration in the area. The substantial hydrothermal alteration in the Lesser Himalaya during advancement of the Main Central Thrust (MCT) and thereby clay mineralization in sliding zones of large-scale landslide are the main causes of large-scale landslides in the highways of central Nepal. This research also suggests that large-scale landslides are the major cause of slope failure during monsoon in the Lesser Himalaya of Nepal. Similarly, hydrothermal alteration is also significant in failure zone of the large-scale landslides. For the sustainable road maintenance in Nepal, it is of utmost importance to study the nature of sliding zones of large-scale landslides along the highways and their role to cause debris flows and slides during monsoon period.

DOI： 10.1007/s00254-008-1420-z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL ACAD SCIENCES  

This paper proposes a preliminary highway alignment optimization model incorporating slope disaster risk management. Previous research in highway alignment optimization has not considered detailed slope instability conditions. Various types of natural disaster-including landslides, slope failure, floods, and earthquakes.-are common in the Himalayan regions because of rugged topography and fragile geology. Construction of highways in the area disturbs naturally formed slopes, resulting in instability on the slope. An inclusive slope failure susceptibility map was prepared by considering various types of landslide-controlling factors including lithology, slope, aspect, land use, drainage density, stream drop, distance to stream, and distance to lineament. In addition to slope failure susceptibility layer, land acquisition cost, slope, land use, and unit cost of earthwork excavation are considered when optimizing highway alignment The process was done in a geographic information system environment in a case study investigating the influence of the slope failure susceptibility condition in alignment optimization. Preliminary alignments were searched in a cost-weighted distance raster created with and without considering slope failure susceptibility condition, whose influence is noticed distinctly with respect to location and length of alignment. Alignments obtained from preliminary optimization were compared with previously proposed alignments, and newly optimized alignments verify the previous studies. The main limitation of this study-that it could not consider all cost functions-will be considered in future work.

DOI： 10.3141/2120-10

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INT UNION GEOLOGICAL SCIENCES  

Roadside slope failure is a common problem in the Himalayan region as road construction activities disturb natural slopes. Therefore, landslide susceptibility zonation is necessary for roadside slope disaster management and planning development activities. In this study, we consider a 53-km section of a major highway in Nepal where road services are suspended for several days in the monsoon season every year A number of methods have been used for landslide susceptibility zonation. We employed a bivariate statistical approach for this study. Relevant thematic layer maps representing various factors (e.g., slope, aspect, land use, lithology, drainage density, proximity to stream and proximity to road) that are related to landslide activity, have been prepared using Geographic Information System (GIS) techniques. A total of 277 landslides (covering a total of 29.90 km(2)) of various dimensions have been identified in the area. A landslide susceptibility map was prepared by overlaying a landslide inventory map with various parameter maps segmented into various relevant classes. The landslide susceptibility index was segmented into five zones, viz. very low, low, moderate, high and very high susceptibility. Landslide susceptibility zonation maps are useful tools for the efficient planning and management of roadside slope repair and maintenance tasks in the Himalayan region.

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

This paper deals with groundwater hydrology at a prominent fracture zone landslide slope (Nuta-Yone landslides) in Japan with an objective to explore an efficient method for the application of landslide stability enhancement measures. The correlation analyses between the hydrological parameters and ground surface movement data at this landslide resulted in low correlation values indicating that the geological formation of the area is extremely complex. For the purpose of understanding the groundwater flow behavior in the landslide area, a three-dimensional transient groundwater flow model was prepared for a part of the landslide slope, where the levels of effectiveness of applied landslide stability enhancement measures (in the form of multilayered deep horizontal drains) are different, and was calibrated against the measured water surface elevations at different piezometer locations. The parameter distributions in the calibrated model and the general directions of the groundwater flow in terms of flow vectors and the results of particle tracking at the model site were interpreted to understand the reasons for variations in effectiveness of existing landslide stability enhancement measures and to find potentially better locations for the implementation of future landslide stability enhancement measures. From the modeling results, it was also understood that groundwater flow model can be effectively used in better planning and locating the landslide stability enhancement measures.

DOI： 10.1007/s10346-008-0121-8

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (conference, symposium, etc.)  

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Language：Japanese   Publisher：The Clay Science Society of Japan  

This paper discusses landslide mechanism in serpentine dominated areas from geotechnical and mineralogical points of view. It first introduces typical features of landslide distribution in the serpentine zone, which is then supported by the discussion encompassing shear strength and mineralogical properties of the clay material involved in inducing serpentine zone landslides. The angles of shear resistance for the weathered serpentine clay samples were found to be comparatively high, which often does not lead to land sliding in gentle slopes, so the chances of smectite or expansive chlorite originated from other rock types being the cause of land sliding were found to be higher. For this reason, comparatively gentle serpentine slopes usually slide through the planes of boundary with other rock types. The dissolution tests on fine powder samples of serpentine revealed the influence of brucite, and the angles of shear resistance decrease notably with the release of ions. Finally, the shear strength and elemental analysis tests on the collected landslide clay samples revealed the influence of chemical weathering on decreased shear strength of clays.

DOI： 10.11362/jcssjnendokagaku1961.46.16

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Publishing type：Research paper (scientific journal)   Publisher：International Union of Geological Sciences  

DOI： 10.18814/epiiugs/2006/v29i1/003

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Language：Japanese   Publishing type：Research paper (other academic)  

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Publisher：The Japanese Geotechnical Society  

The rates of displacement of most landslides in Shikoku Region of Japan, which can be categorized as being creeping in nature, considerably increase after a rise in groundwater level due to rainfall. The rise of groundwater level in landslide slopes generally results in the increase of weight of the slope material and pore-water pressure in the slip layer. As the increase in normal stress results in the rise of shear strength of soil, the increased in the weight of slope material may be considered insignificant for causing the accelerated displacement. The increase in pore-water pressure, on the other hand, results in decreased effective normal stress casuing significant loss in the soil strength. This paper attempts to explain the failure of slip layer soil during rise in pore-water pressure by employing triaxial compression tests under constant deviator stress but varied pore-water pressure.

DOI： 10.11512/jiban.JGS39.0.2153.0

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

In general, the strength behavior of clay or clayey soil is evaluated based on the state of normal consolidation and over-consolidation. It is however attempted to recognize in this paper that normally consolidated state of a disturbed sample of clayey soil cannot be defined by a single curve in the e-log p diagram. Unlike remolding of a pre-consolidated clay sample at very high water content, remolding under controlled voids ratio may result in a different consolidation behavior. Such a phenomenon may also take place in natural grounds such as landslide in which the slip layer clay undergoes remolding due to large deformation and dissipation of developed pore water pressure causing decreased voids ratio under the same effective overburden pressure. Therefore, attempts are made to explain the strength behavior of non-cohesive clayey soil based on a newly introduced parameter, which is found to define the state of consolidation of the clay under test and commonly explain the shear strength characteristic.

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Language：Japanese   Publisher：The Japan Landslide Society  

DOI： 10.3313/jls1964.38.3_248

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Other Link： https://jlc.jst.go.jp/DN/JALC/00370389118?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

Despite following the design standards for cut slopes, construction of the expressway linking Tokushima and Matsuyama cities in Shikoku Island of Japan has caused a number of slope failures and activated many landslides, especially in the Izumi Geological Belt that passes east west across the island. Observation of the nature of slope failures interested the authors to carry out some geotechnical and mineralogical studies, which could reveal the actual mechanism of the instability in the slope soil mass in the Izumi Belt. Laboratory tests on collected soil samples made it clear that one of the reasons for unexpected failure was expansive clay mineral content. Smectite concentrations were found in most of the soil samples; however, samples that did not have expansive clay minerals contained weaker clay minerals like mica whose sheet like structure makes them resist only a little shear stress.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

Many prediction methods for rainfall induced slope failures have so far been proposed but their application in an effective way is yet to be practiced. Predicting any natural disaster has always been a challenging task to the engineers. Only 10 minutes before the occurrence of a soil disaster will be more than sufficient to save, if not the property, the human life. So as a prediction method for rainfall induced slope failures by critical rainfall criterion, measurement of suction due to unsaturated state of soil mass at a possible failure site was carried out. The data obtained were then utilized to establish initial conditions for the calculation of critical rainfall, which is a key to predict the rainfall-induced slope failure at a particular area.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：A A BALKEMA PUBLISHERS  

Accumulated amount of surplus soil from different construction sites, especially in tunneling, slope cutting, and underground excavation works in Japan is extremely high. As a waste material, this huge amount of soil creates many problems in its disposal, and therefore must be utilized in such a way that the environment remains unaffected. One of the recently practiced surplus soil utilization areas is the land reclamation work near coastal areas. However, half of the surplus soil produced being loose and weak in strength, it needs to be strengthened prior to the compaction. This paper relates to a study that elaborates the improved strength characteristics of some local surplus soils in Ehime Prefecture by the addition of slag, which also is an industrial waste. Also studied is the influence of mineral components on the strength attained by the addition of slag and some other cementing materials.

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Language：English   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：English   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：English   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：Japanese   Publishing type：Research paper, summary (national, other academic conference)  

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Language：English   Publisher：Springer Japan  

This book presents landslide studies using the geographic information system (GIS), which includes not only the science of GIS and remote sensing, but also technical innovations, such as detailed light detection and ranging profiles, among others. To date most of the research on landslides has been found in journals on topography, geology, geo-technology, landslides, and GIS, and is limited to specific scientific aspects. Although journal articles on GIS using landslide studies are abundant, there are very few books on this topic. This book is designed to fill that gap and show how the latest GIS technology can contribute in terms of landslide studies. In a related development, the GIS Landslide Workshop was established in Japan 7 years ago in order to communicate and solve the scientific as well as technical problems of GIS analyses, such as how to use GIS software and its functions. The workshop has significantly contributed to progress in the field. Included among the chapters of this book are GIS using susceptibility mapping, analyses of deep-seated and shallow landslides, measuring and visualization of landslide distribution in relation to topography, geological facies and structures, rivers, land use, and infrastructures such as roads and streets. Filled with photographs, figures, and tables, this book is of great value to researchers in the fields of geography, geology, seismology, environment, remote sensing, and atmospheric research, as well as to students in these fields.

DOI： 10.1007/978-4-431-54391-6

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Landslides have been one of the major natural disasters in most countries in the world. Indonesia has experienced landslides events annually in its mountainous areas and has been generating increasing number of casualties in recent years. One way of preventing the number of casualties from these landslides is by identifying those landslides prone areas and mitigates it by providing susceptible maps. Remote Sensing (RS) and Geographic Information Systems (GIS) are 2 growing modern technologies that have been used by many researchers in the provision of Landslides Susceptibility Maps (LSM). LSM has been created by many kinds approach by simple methodology like overlaying several parameters layers in GIS to combined methodologies such as using statistical approach and validation with remote sensing images or ground survey. The study area covers a mountainous area named Bawakaraeng and Lompobattang Mountain in South Sulawesi Province, Indonesia where rock formations are dominated by Miocene erupted volcanic. The objective of this research is trying to enhance the existing LSM created using frequency ratio model with higher resolution raster image of causal factors parameters used to create the LS index maps. In this research, we attempted to use the raster image created from Differential Interferometry of Synthetic Aperture Radar (SAR) image processing of ALOS PALSAR1 images of DInSAR repeated-pass method. The raw data is SAR level 1 data with 5 scenes of different acquisition year of 2007, 2008, 2009, 2010, and 2011 of similar seasons. We have processed 3 pairs of SAR and the raster image generated have indicated areas where slight surface displacement have occurred and confirmed where cracks were found that initiated surface movement of future landslides. This image was used to validate the landslide incidence location and as one parameter of the causal factors in frequency ratio analysis in enhancing the creation of LSM. The result showed zone of prone areas to landslides graded based on the Landslide Susceptibility Index.

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DOI： 10.1179/1938636213Z.00000000044

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Language：English  

Many researchers have studied creeping behaviour of landslide soils in the laboratory using both odometer and triaxial tests
however in most cases, they have only concentrated on the pre-peak creep behaviour of soil, which does not adequately explain the creep movement of landslides that undergo large displacements at close-to-residual state of shear. This necessitates the importance of further studying creep behaviour of clayey soils in residual-state of shear. In order to investigate creep behaviour of clayey soils, a method of residual-state creep test in a modified torsional ring shear machine is developed in laboratory, which can simulate the creeping behaviour of a large-scale landslide. This paper discusses on the typical results obtained from four representative landslide soils, i.e., commercially available Kaolin clay and three other samples from the landslide area in Japan and Nepal which have higher percentage of smectite, chlorite, and mica. Finally, possibilities towards displacement prediction are discussed. © Springer-Verlag Berlin Heidelberg 2013.

DOI： 10.1007/978-3-642-31445-2-83

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The usual way to specify the impact load onto the rockfall protective structures has been through the impact energy (kinetic energy) of the falling rock-boulder. The same philosophy was adopted during the full-scale test campaign of a newly developed interceptive system in Japan, known as the Long-span Pocket-type Rock-net (LPR). The LPR was required to resist fully the specified kinetic energy that was achieved via an arbitrary combination of the mass and the velocity (or falling height) of the impacting concrete block. However, it is very practical that there exist other variables that may independently characterize the impact of rockfall onto the protective structures while giving the same specified impact energy! Few important of them could be the density of rock-block, its velocity, or size, idealized block-shape, impact point, multi-rock impact, etc. Their effects should be scientifically quantified and appropriately incorporated either explicitly or implicitly (approximately) in the design. Setting this hypothesis, the authors carried out a numerical parametric study involving the nonlinear dynamic analyses using the Finite Element code of LS-DYNA, and the effects of various characteristic-parameters were successfully depicted. Finally, implicated from the discovered effects, a proposal on the improvement in the state-of-the-practice method of specifying the impact load for the design and targeted design code preparation of LPR structures is presented, wherein there shall be other independent variables as well in addition to the usually specified kinetic energy of falling rock block.

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Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese  

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Language：English  

Various studies in the past have revealed that the percentage of landslides and related failures occuring in low to middle class mountain ranges of Nepal in Central Himalaya is far greater than that occurring in any other parts of the country. Especially, the landslides and slope failures including debris flows that frequently damage road infrastructure in Central Nepal draw significant attention in terms of national concern over economic loss and public suffering. The most important national road network in Nepal connecting the capital area to rest of the business centers and dense settlement areas in southern plains frequently suffers from this problem. However, the efforts to study these landslides and their engineering properties to go for appropriate preventive techniques are insiginificant. With an aim to understand shear characteristics of clay material of landslides along this road network, this paper addresses land sliding mechanism in terms of material shear behavior and mineralogical influence. A total of 31 locations of landslides and failure sites were investigated for field verification and soil sampling. Due to field-related difficulties and limited resources, however, soil sampling was possible at about 15 locations only. The collected samples were then tested in ring shear apparatus for peak and residual shear strength parameters and in x-ray diffractometer for minerological composition to reveal the influence of chlorite and mica like weak minerals on the shear strength of landslide clays. © 2009 IOS Press.

DOI： 10.3233/978-1-60750-031-5-237

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Language：Japanese  

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Language：English   Publisher：Springer Berlin Heidelberg  

Various investigations on tectonically-induced landslides in Shikoku Region of West Japan have been carried out, most of which conclude at tectonic activities through the major tectonic faults and enhanced rock mineral decomposition as being mainly responsible for the landslide occurrence. This paper looks into strength parameters of the landslide clays, as measured in ring shear apparatus, from clay mineralogical point of view. As a result of strength tests and X-ray diffraction analysis, it is found that the drop from peak to residual friction angles for the tested samples reaches as high as 20°, and the residual strength of the landslide clays was found to decrease with higher amount of expansive clay minerals, which was estimated as being relative to chlorite mineral. © 2007 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/978-3-540-70965-7_13

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Publisher：The Japan Landslide Society  

DOI： 10.3313/jls.43.376

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Other Link： https://jlc.jst.go.jp/DN/JALC/00297740061?from=CiNii

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Language：Japanese  

Shikoku has steep mountains and weak geological conditions, which often causes problems in various construction works. In addition, concentration of population is quite common in plain areas, which risks a peat loss of lives during natural disasters such as earthquakes and floods. It may therefore be important to have an up-to-date geo-information database so as to overcome potential problems during geo-hazards including the Nankai Earthquake expected to hit Shikoku within a few tens of years. This paper is based on the outcomes of a committee led by Shikoku Regional Development Bureau and formed in 2003 to study the ways to utilize the geo-information data in Shikoku.

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10444118

Language：Japanese   Publisher：土質工学会  

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Language：English   Publisher：SPRINGER-VERLAG BERLIN  

Various investigations on tectonically-induced landslides in Shikoku in west Japan have been carried out, most of which conclude at tectonic activities through the major fault lines and enhanced rock mineral decomposition as being mainly responsible for the landslide occurrence. Little work is found, however, on the mechanism of their creep activation and role played by the expansive clay minerals. This paper aims at looking into strength parameters of the landslide clays from mineralogical point of view. In addition, the strength behavior is analyzed from inclusion of weaker clay minerals such as smectites. It is found that the drop from pea to residual friction angles for the tested samples reaches as high as 20 degrees. In addition, the residual strength of the landslide clays was found to decrease with higher amount of expansive clay minerals, which was estimated as being relative to chlorite mineral from the XRD patterns. Moreover, the presence of non-crystalline clay materials was found to considerably lower the friction angles of the landslide soils.

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Language：Japanese   Publisher：The Japanese Geotechnical Society  

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Language：English   Publisher：A A BALKEMA PUBLISHERS  

Median Tectonic Line is a first class and very active fault line in Japan. Large fractured zones due to the plate movement have developed along this line. With the construction of Shikoku Jukando expressway along it, many large-scale landslides have also been occurring. Therefore, it was supposed to be very important to carry out a study on landslide behavior and landslide soil characteristics along this line so that suitable countermeasure works could be designed, and the safety of the expressway could be increased. After the study, it was found that phi' of landslide clays along the fractured zone was relatively small, in a range of 20 degrees-35 degrees, and the drop from phi' to phi(r) was notably big, about 15 degrees. This small angle of shear resistance and a big drop from phi' to phi(r) were supposed to be some of the reasons why landslide countermeasure works along MTL are generally difficult.

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Language：English   Publisher：A A BALKEMA PUBLISHERS  

Many landslides are active in different parts of Japan. So far, the study shows that the landslides in Japan based on the base rocks can be classified into three major groups: Tohoku Region green tuff landslides, Hokuriku-Hokubu Kyushu tertiary landslides, and Tectonic Line fractured zone hard rock landslides. A study was carried out to investigate the effect of minerals on the strength of landslide clays of all these landslides. It was also studied whether or not the results of the remolded and undisturbed samples are same. The strength characteristics of landslide clays from fractured zone and tertiary landslides were found to be nearly similar which is because of the similarity in clay mineral content. The phi' and phi r for the landslide clays containing smectite were very small ranging from 10 degrees to 20 degrees, whereas those for the landslide clays containing chlorite, illite, and mica as their mineral content were about 15 degrees to 25 degrees.

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Country：Japan

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Award type：Award from publisher, newspaper, foundation, etc.  Country：Japan

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Award type：International academic award (Japan or overseas) 

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