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

DOI： 10.11187/ijjsrm.240202

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

Abstract

Soil is one of the most important construction materials in the world. It has been effectively exploited for various purposes, such as building social infrastructures, growing agricultural products, and promoting many other important activities that can be useful for human life. The nature of the soil is uncertain from one place to another due to its physical, chemical, and mechanical properties. The expansive type of soil is the most problematic soil and causes damage to the foundations of roads and buildings. On the other hand, solid agricultural waste is widely available and is also a serious problem for the environment and its ecosystem. Therefore, improving the property of problematic soil by using sustainable, locally available, and low-cost agricultural waste materials is required. This paper aims to review the existing knowledge and practices from the recently published state-of-the-art journals related to expansive soil stabilization by agricultural waste additives and to support the findings with scientific data analysis. The effect of using agricultural waste additives such as coffee husk, rice husk, sawdust, wheat straw, cornhusk, sugarcane bagasse, and bamboo powder was carefully evaluated in terms of geotechnical characteristics, and strength parameters. As a result of the review, agricultural waste additives improved California Bearing Ratio (CBR), Plastic Index (PI), and Unconfined Compressive Strength (UCS) values, significantly lowered Optimum Moisture Content (OMC) and increased the Maximum Dry Density (MDD) of the soil. Furthermore, the effects of microstructural composition, morphology, and changes in expansive soils treated with agricultural waste additives were analyzed based on the XRD test results and SEM image analysis.

DOI： 10.1186/s40703-023-00194-x

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Other Link： https://link.springer.com/article/10.1186/s40703-023-00194-x/fulltext.html

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

The liquefaction of soil occurs when a soil loses strength and stiffness because of applied stress, such as an earthquake or other changes in stress conditions that result in a loss of cohesion. Hence, a method for improving the strength of liquefiable soil needs to be developed. Many techniques have been presented for their possible applications to mitigate liquefiable soil. Recently, alternative methods using biopolymers (such as xanthan gum, guar gum, and gellan gum), non-traditional additives, have been introduced to stabilize fine-grained soils. However, no studies have been done on the use of carrageenan as a biopolymer for soil improvement. Due to of its rheological and chemical structure, carrageenan may have the potential for use as a biopolymer for soil improvement. This research aims to investigate the effect of adding carrageenan on the soil strength of treated liquefiable soil. The biopolymers used for comparison are carrageenan (as a novel biopolymer), xanthan gum, and guar gum. Then, sand samples were made in cylindrical molds (5 cm x 10 cm) by the dry mixing method. The amount of each biopolymer was 1%, 3%, and 5% of the total sample volume with a moisture content of 20%, and the samples were cured for seven days. In terms of observing the effect of temperature on the carrageenan-treated soil, several samples were prepared with dry sand that was heated in an oven at various temperatures (i.e., 20°C to 75°C) before mixing. The samples were tested with the direct shear test, UCS test, and SEM test. It can increase the cohesion value of liquefiable soil by 22% to 60% compared to untreated soil. It also made the characteristics of the liquefiable increase by 60% to 92% from very loose sandy soil (i.e., ϕ=29°) to very dense sandy soil. Carrageenan was also shown to have a significant effect on the compressive strength and to exceed the liquefaction limit. Based on the results, carrageenan was found to have the potential for use as an alternative biopolymer.

DOI： 10.12989/gae.2023.33.2.221

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals  

DOI： 10.2320/matertrans.m-m2022813

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

DOI： 10.1016/j.sandf.2022.101207

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

DOI： 10.1016/j.rockmb.2022.100007

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

DOI： 10.1007/s13349-022-00620-1

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Other Link： https://link.springer.com/article/10.1007/s13349-022-00620-1/fulltext.html

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

DOI： 10.1016/j.gete.2022.100372

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Mining and Materials Processing Institute of Japan  

DOI： 10.2473/journalofmmij.138.134

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Mining and Materials Processing Institute of Japan  

DOI： 10.2473/journalofmmij.138.70

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Mining and Materials Processing Institute of Japan  

DOI： 10.2473/journalofmmij.138.84

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Geotechnical Society  

DOI： 10.3208/jgssp.v09.cpeg045

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

A simple monitoring method for observing slope movement and deformation can be performed with tilt sensors. A more efficient monitoring method, using a type of wireless communication called LPWA (low-power wide area) network technology, has also recently become available. In the present study, a monitoring system was developed that combines tilt sensors and LPWA network technology for measuring the movement of slopes and sending the information through wireless communication. First, radio wave propagation experiments were conducted to find the proper location for the gateway device of the monitoring system. Then, in March 2018, the developed system that consists of tilt and water-level sensors and the wireless communication of LPWA was installed at an observation site. Since the installation, the data from the tilt sensors have been successfully collected through LPWA, and a slope failure was unexpectedly observed at the observation site during the Heavy Rain Event of July 2018, which caused severe disasters, particularly from western Japan to the Tokai region. Using the data from the tilt sensors, the rainfall data, and the groundwater level, the slope failure was analysed. A site investigation was conducted, and the shear strength parameter was examined using back analysis method. In conclusion, the developed system using sensors and LPWA has continued to efficiently monitor the movement of the targeted slope, but the collection of additional data will be required to increase the reliability of the system.

DOI： 10.1007/s13349-021-00494-9

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Other Link： https://link.springer.com/article/10.1007/s13349-021-00494-9/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Journal of Geomate  

DOI： 10.21660/2020.72.9481

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

The comprehensive exploitation of geothermal fields has an impact on the productivity of the reservoirs. To realize sustainable steam production, changes in the rock temperature need to be predicted and controlled. A coupled thermo-hydro-mechanical (THM) model employing COMSOL Multiphysics was proposed to study the characteristics of heat transfer, fluid flow, and solid deformation at the Lahendong geothermal field, in North Sulawesi, Indonesia. The numerical results were compared with analytical and measured data in order to validate the numerical simulation. Based on the results, the predicted temperatures of the production wells showed significant decrease with the production time. In addition, a reduction in the reservoir temperature leads to lower specific gross electrical power within the production well, which should significantly reduce the sustainability of the power plant.

DOI： 10.3390/en13123282

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

DOI： 10.1007/s10596-020-09948-3

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Other Link： http://link.springer.com/article/10.1007/s10596-020-09948-3/fulltext.html

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

DOI： 10.2472/jsms.69.236

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

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

A multi-physics numerical model was developed to predict the fluid flow and mass transport behavior of rock fractures under coupled thermal-hydraulic-mechanical-chemical (THMC) conditions. In particular, the model was employed for the purpose of describing the evolution of permeability and reactive transport behavior within rock fractures by taking into account the geochemical processes of the free-face dissolution and the pressure dissolution. In order to examine the capability of the developed model, the model was applied to replicate the experimental measurements of the evolution in hydraulic aperture, permeability, and element concentrations obtained from two flow-through experiments using single granite and mudstone fractures. The model predictions for the granite experiment were able to follow the actual data for the evolution in hydraulic aperture and effluent element concentrations without adopting any fitting parameters that are often used in other THMC coupled models obtained from literature. Furthermore, the model succeeded in replicating the actual changes in fracture permeability and effluent element concentrations within the mudstone fracture. Although some uncertain mismatches between the experiments and the model predictions, such as changes in the concentrations of several elements (i.e., Na and K concentrations in the granite fracture and Al in the mudstone fracture) were remaining at this stage, the developed model should be valid for evaluating the evolution in the fluid flow and mass transport behavior within rock fractures induced by mineral dissolution under stress- and temperature-controlled conditions.

DOI： 10.1016/j.ijrmms.2018.04.015

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Society for Rock Mechanics  

The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. In this case, as the rock mass around the openings will receive thermal hysteresis of low temperatures, it is necessary to obtain strength and deformation characteristics of rocks after receiving thermal hysteresis of low temperatures to consider the thermal behavior of rock mass around openings and the stability of openings. In this study, strength and deformation characteristics of some types of rocks were examined after receiving thermal hysteresis of low temperatures. Using the results of the experiments, temperature and stress distribution around openings were analyzed. From the results of analysis, it was found that in the case of receiving thermal hysteresis, crack length and freezing zone are about same as in the case of not receiving thermal hysteresis.

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

This study evaluated the applicability of natural zeolite for the removal of the NH-forms in the enzyme-mediated calcite precipitation technique. The natural zeolite of mordenite was added to prepared grouting solutions composed of urea and urease and mixed thoroughly using a rotation table for the mixing times of 0.5, 1.0, and 2.0 h. Then, the concentrations of evolving NH-forms in the solutions were measured. The effects of the presence of zeolite on the amount and the mineralogical substance of the precipitated minerals were also evaluated by X-ray powder diffraction and scanning electron microscopy analyses. Sand samples were treated with the grouting solutions containing zeolite, and the improvement in strength was assessed. It was found that utilizing zeolite in grouting solutions can reduce the concentration of NH-forms. A significant reduction in the concentration of NH-forms was obtained. The addition of 10 g natural zeolite/L solution, combined with the 2-h mixing time, resulted in removal efficiencies of 75% and 45% in reagent concentrations of 0.5 and 1.0 mol/L, respectively. Mechanical test results showed that the grouting solutions also brought about a significant improvement in the soil strength. A precipitated material, comprising 9% of the sand mass, was produced by three pore volume (PV) injections of the grouting materials, which showed an unconfined compressive strength of 300 kPa.

DOI： 10.3390/geosciences7030061

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2473/journalofmmij.133.132

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

This study discussed the possible optimization of enzyme-mediated calcite precipitation (EMCP) as a soil-improvement technique. Magnesium chloride was added to the injection solution to delay the reaction rate and to improve the homogenous distribution of precipitated minerals within soil sample. Soil specimens were prepared in 1m PVC cylinders and treated with the obtained solutions composed of urease, urea, calcium, and magnesium chloride, and the mineral distribution within the sand specimens was examined. The effects of the precipitated minerals on the mechanical and hydraulic properties were evaluated by unconfined compressive strength (UCS) and permeability tests, respectively. The addition of magnesium was found to be effective in delaying the reaction rate by more than one hour. The uniform distribution of the precipitated minerals within a 1-m sand column was obtained when 0.1 mol/L and 0.4 mol/L of magnesium and calcium, respectively, were injected. The strength increased gradually as the mineral content was further increased. The permeability test results showed that the hydraulic conductivity was approximately constant in the presence of a 6% mineral mass. Thus, it was revealed that it is possible to control the strength of treated sand by adjusting the amount of precipitated minerals.

DOI： 10.12989/gae.2017.12.5.803

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

<p>It is of significant importance to safely isolate the radioactive wastes from the human environments. Entombment of the wastes in deep subsurface may be a plausible solution on this issue, and will be adopted in the countries where the nuclear power plants are in operation. Before burying them in the targeted rocks, the longterm evolution of the mechanical and the hydraulic properties of the targeted rocks should be predicted with a certain precision. To this end, in this study we examined the change of the apparent secant elastic modulus and the permeability of a single fracture in the Berea sandstone and the Horonobe mudstone samples under the relatively high temperature and confining pressure conditions. The apparent secant elastic modulus of the mudstone increased with the increase of the holding time and specifically, the values at 90 ºC were greater than those at 25 ºC, while that of the sandstone little increased with time. In contrast, the permeability of both the mudstone and sandstone samples monotonically decreased with time, and the rates of the permeability reduction were close among all the samples. The increase of the elastic modulus and the decrease of the permeability may be attributed to the chemomechanical processes such as pressure solution and the mechanisms explaining the changes should be clarified. Although the mechanisms are still ambiguous, the increase of the elastic modulus and the permeability reduction with time may improve the integrity of the targeted rocks.</p>

DOI： 10.2473/journalofmmij.133.53

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

<p>Rockfall is an important geo-hazard of mountainous area in Japan and has gained greater attention and recognition due primarily to the severe accidents and mortalities happening in roadways and railways. Rock fall countermeasures are classified into preventive works and protectors. In rock protectors that have high rigidity, there are rock protecting fence, rock protecting wall and rock shed, etc. On the other hand, there is a pocket type rock net which excels in the application condition of the topography and absorbs energy by deforming itself. The standard absorbable energy of the pocket type rock net is 100 kJ. Then, the rock net is designed so that the absorbed energy exceeds the falling rock energy. However, in recently, many types of rock net such as high energy type and long span type have been developed, and there are cases where conventional design methods cannot be applied. In this study, the performance of a long span pocket type rock net was evaluated by dynamic analysis. Firstly, the physical properties of the rock net members were identified by comparing the results of the real scale field experiments with the dynamic analyses. Then, the relationships between the displacement of the net and the net width, the maximum tensional force of a horizontal rope and the rope position, etc. were evaluated by the dynamic analyses. Typically, these evaluations by conventional design methods are laborious and are carried out using the results of real scale field experiments. However, the current study revealed that the predictions by the dynamic, numerical analyses showed the validity of the performance evaluation by this means.</p>

DOI： 10.2473/journalofmmij.133.45

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

The effectiveness of magnesium as a substitute material in enzyme-mediated calcite precipitation was evaluated. Magnesium sulfate was added to the injecting solution composed of urea, urease, and calcium chloride. The effect of the substitution on the amount of precipitated materials was evaluated through precipitation tests. X-ray powder diffraction and scanning electron microscopy analyses were conducted to examine the mineralogical morphology of the precipitated minerals and to determine the effect of magnesium on the composition of the precipitated materials. In addition to calcite, aragonite and gypsum were formed as the precipitated materials. The effect of the presence of aragonite and gypsum, in addition to calcite, as a soil-improvement technique was evaluated through unconfined compressive strength tests. Soil specimens were prepared in polyvinyl chloride cylinders and treated with concentration-controlled solutions, which produced calcite, aragonite, and gypsum. The mineralogical analysis revealed that the low and high concentrations of magnesium sulfate effectively promoted the formation of aragonite and gypsum, respectively. The injecting solutions which produced aragonite and calcite brought about a significant improvement in soil strength. The presence of the precipitated materials, comprising 10% of the soil mass within a treated sand, generated a strength of 0.6 MPa.

DOI： 10.3390/cryst7020059

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

CO2 geological storage has been studied as a countermeasure against global warming. When the injected CO2 reacts with rock minerals, some portion of it may ultimately precipitate to carbonate minerals, such as calcite, and become trapped within the injected reservoir. Although it is of significant importance to examine how the trapped minerals exert an influence on the mechanical, hydraulic, and transport properties of the targeted reservoir rocks, because the minerals may affect the integrity of these rocks, such works are quite sparse in the literature. In this study, the influence of mineral trapping on the evolution of the physical properties was evaluated by replicating the precipitation of calcite that may occur in the mineral-trapping process. The calcite precipitation was enhanced artificially to occur within the void spaces of Berea sandstone. Subsequently, the treated samples were examined through mechanical and permeability experiments. The experimental results revealed that an approximately 10% substitution of the void spaces by the precipitated calcite increased the elastic modulus twofold and the uniaxial compressive strength (UCS) by 20%, and decreased the permeability by one order of magnitude. A cementation theory revealed the process of the calcite precipitation occurring on the free-surface of grains. Predictions of the permeability, using the Kozeny-Carman equation, suggest that variations in permeability imply an increase in surface roughness of the composed grains due to calcite precipitation. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijggc.2016.11.018

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The optimum condition of enzyme-mediated calcite precipitation has been evaluated for its possible application as a soil improvement technique. Magnesium chloride (MgCl 2 ) and magnesium sulfate (MgSO 4 ) were substituted to the grouting solution composed of urease, urea, and calcium chloride (CaCl 2 ), and its effects on the precipitation process, amount, and the mineralogical substances of the precipitated materials were investigated. The evolution of the strength of treated sand was also evaluated through unconfined compressive strength (UCS) tests. The substitution of magnesium compounds was found to be able to augment the precipitated amount and reduce the hydrolysis rate of urea. The mineralogical analysis indicated that the addition of magnesium to the grouting solution was a potential method for promoting the formation of aragonite. Furthermore, the formation of gypsum was also promoted when magnesium sulfate was substituted. The mechanical analysis showed that the producing of the high precipitated amount resulted in the significant improvement in the strength of the treated sand. The relation between the UCS of the treated soil and the precipitated mass indicated that the strength could be controlled by the precipitated mass within the soil.

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

A coupled THMC numerical model has been developed to examine the long-term change in permeability of the porous sedimentary rocks that are assumed to be composed purely of quartz. Specifically, the chemo-mechanical process of the pressure solution was incorporated into the model. The developed model was validated by replicating the existing experimental measurements of the porosity reduction and the evolving silica concentration. Subsequently, by simulating the burial of high-level radioactive wastes in the deep subsurface, namely, by applying the simulated confining pressure and temperature conditions, the long-term evolution of the rock permeability was predicted. The model predictions clearly showed a significant influence of the pressure dissolution on the change in permeability with time. The predicted permeability of the rocks close to the wastes decreased by one order of magnitude in 10(4) years when considering the pressure dissolution, while the permeability changed little during the same period when the pressure dissolution was not considered. This reduction should delay the dispersion of the radioactive materials dissolved in the groundwater. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijmms.2016.03.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media S.A.  

The optimization of enzyme-mediated calcite precipitation was evaluated as a soil-improvement technique. In our previous works, purified urease was utilized to bio-catalyze the hydrolysis of urea, which causes the supplied Ca2+ to precipitate with CO3 2- as calcium carbonate. In the present work, magnesium chloride was newly added to the injecting solutions to delay the reaction rate and to enhance the amount of carbonate precipitation. Soil specimens were prepared in PVC cylinders and treated with concentration-controlled solutions composed of urea, urease, calcium, and magnesium chloride. The mechanical properties of the treated soil specimens were examined through unconfined compressive strength (UCS) tests. A precipitation ratio of the carbonate up to 90% of the maximum theoretical precipitation was achieved by adding a small amount of magnesium chloride. Adding magnesium chloride as a delaying agent was indeed found to reduce the reaction rate of the precipitation, which may increase the volume of the treated soil if used in real fields because of the slower precipitation rate and the resulting higher injectivity. A mineralogical analysis revealed that magnesium chloride decreases the crystal size of the precipitated materials and that another carbonate of aragonite is newly formed. Mechanical test results indicated that carbonate precipitates within the soils and brings about a significant improvement in strength. A maximum UCS of 0.6 MPa was obtained from the treated samples.

DOI： 10.3389/fbioe.2016.00037

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PubMed

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

This study evaluates the potential of improving an insitu calcite grouting technique. The grout is composed of an equimolar solution of urea CaCl2 and an enzyme named urease. We examine the distribution of the grout materials and precipitated calcite within sand columns with a diameter of 5 cm and a height of 100 cm. In the first series of experiments, the concentration distributions of the individual grout materials (i.e., urea, CaCl2 and urease) within the sand specimen are evaluated. In the second series of experiments, an enzyme-reagent mixed solution (i.e., grout) is injected into the sand columns to evaluate the distribution of calcite. Sand samples are collected from various vertical locations within the treated columns and the amount of precipitated calcite is evaluated. Furthermore, attempts are made to achieve the uniform distribution of the injected grout and hence uniform calcite distribution throughout the specimen. The results show that a uniform distribution of the grout materials up to a distance of 1 m from the inlet is achievable. It is also observed that a relatively uniform distribution of calcite is achievable as long as the rate of calcite precipitation is well controlled. (C) 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sandf.2015.10.015

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

As considering the safe isolation of high level radioactive wastes, the long-term evolution of the hydraulic properties of rocks should be examined because a thermo-hydro-mechano-chemical processes are active under such conditions. In this study, a coupled THMC numerical model, especially by considering the pressure solution mechanism, has been developed to examine the long-term change of the permeability in sedimentary rocks that are assumed to be purely composed of quartz. The model predictions show a significant influence of the pressure solution on the permeability change with time. The predicted permeability decreases by one order of magnitude in 104 years when considering the pressure solution. The monotonic decrease of the permeability is congruent with the observed behavior in the literature.

DOI： 10.2208/jscejge.71.292

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER GEOPHYSICAL UNION  

In this study, a series of long-term, intermittent permeability experiments utilizing Berea sandstone and Horonobe mudstone samples, with and without a single artificial fracture, is conducted for more than 1000 days to examine the evolution of rock permeability under relatively high-temperature and confining pressure conditions. Effluent element concentrations are also measured throughout the experiments. Before and after flow-through experiments, rock samples are prepared for X-ray diffraction, X-ray fluorescence, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy to examine the mineralogical changes between pre and postexperimental samples, and also for microfocus X-ray CT to evaluate the alteration of the microstructure. Although there are exceptions, the observed, qualitative evolution of permeability is found to be generally consistent in both the intact and the fractured rock samplesthe permeability in the intact rock samples increases with time after experiencing no significant changes in permeability for the first several hundred days, while that in the fractured rock samples decreases with time. An evaluation of the Damkohler number and of the net dissolution, using the measured element concentrations, reveals that the increase in permeability can most likely be attributed to the relative dominance of the mineral dissolution in the pore spaces, while the decrease can most likely be attributed to the mineral dissolution/crushing at the propping asperities within the fracture. Taking supplemental observations by microfocus X-ray CT and using the intact sandstone samples, a slight increase in relatively large pore spaces is seen. This supports the increase in permeability observed in the flow-through experiments.

DOI： 10.1002/2014WR016427

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

This study discusses the possible application of enzyme mediated calcite precipitation, EMCP, as a soil-improvement technique. It explains the experimental works on this EMCP technique. The first part of this paper addresses the different methods for quantifying the amount of calcite precipitated within sand. Two methods, namely, the thermal decomposition method and the CO2 volume evaluation method, are examined. These methods serve to evaluate the calcite distribution within the treated sand. The second part of this paper explains the experimental procedures and the results of drum-can experiments. Homogenous sand specimens, with a diameter of 57 cm and a height of 60 cm, are prepared inside a steel drum-can. A grout solution, comprising urea, urease, and CaCl2, is injected into the centre of the sand specimens. Subsequently, the improved samples within the specimens are collected and their compressive strength is evaluated. The maximum measured unconfined compressive strength is 380 kPa. An attempt is made to relate the improved mechanical properties of EMCP-treated sand to the amount of mineralized carbonate. The obtained calcite-strength relation is found to be in close agreement with the relation obtained in previous literature. (C) 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sandf.2015.02.018

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

CCS has been expected as a countermeasure against global warming in recent years. When the injected CO₂ reacts to rock minerals, it may form secondary minerals such as calcite, which is called mineral trapping of CO₂. It is of significant importance to examine how the mineral trapping exerts an influence on the physical properties in the targeted reservoir rocks because the trapped minerals may change the strength, deformability, and permeability of the reservoir rocks, although such works are quite sparse in literature. In this study, the influence of the mineral trapping on the evolution of physical properties has been evaluated by replicating precipitation of calcium carbonate that may occur in the mineral trapping. The results of mechanical and permeability experiments show that the change of the mechanical and hydraulic properties is significant even if the amount of calcite precipitation is relatively small.

DOI： 10.2473/journalofmmij.131.497

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Other Link： http://hdl.handle.net/2433/217353

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

In this work, the soil-ground solidification by calcium carbonate precipitation has been examined utilizing a urea hydrolysis enhanced by urease. Firstly, a suite of the small cylinder tests (50 mm in diameter and 100 mm in height) was conducted to evaluate the evolution of mechanical properties in the im-proved sand soils mediated by the grout injection. The results show that the strength of the improved samples increases with increase of the amount of calcium carbonate precipitated. Specifically, a uniaxial compressive strength of 3.4 MPa was obtained in the sample with approximately 4 wt.% precipitation against the sand weight. Secondly, drum-can tests (560 mm in diameter and 600 mm in height) were per-formed to examine the validity of this technique. It is concluded that the current technique may be ap-plicable to real fields although the strength of the improved sand should be well-controlled prior to the in-situ application.

DOI： 10.2208/jscejge.70.290

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

In radioactive waste disposal, tunnel passing through the ground with high geothermal region, and hot water temporary storage system, the rock mass around the openings will be influenced by coupled chemo-mechanical behavior induced by high temperatures. Then, rock fractures may be hydraulic weakness on low-permeability rock mass. Therefore, the coupled behavior should be examined to evaluate hydraulic property of rock fractures. In this study, flow-through experiments on a single fracture in granite have been carried out under confining pressure and temperature conditions controlled. The fracture permeability monotonically decreased with time at room temperature, and reached a quasi-steady state. Then, after the temperature was raised to 90 ºC, the permeability decreased again throughout the rest of the experiments. The elemental concentrations in fluid samples taken from the outlet were evaluated by ICP-AES. The elemental concentrations increased with increase of temperature. Thus, this behavior should be attributed to coupled chemo-mechanical effects. Meanwhile, another suite of sustained loading experiments using the same granite has been conducted under controlled temperature, confining pressure and mineral dissolution conditions for the purpose of evaluating the deformation behavior of rock fractures. From the tests results, it is found that the difference in compression behavior of the fractures is very small for all the conditions. However, particularly, it is found that displacement of the fractured rock sample under the wet and high temperature conditions is larger than those under the other conditions. The reason for this may be due to microscopic failure and mineral dissolution at the asperity contact areas.

DOI： 10.2473/journalofmmij.129.485

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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)  

A grouting technique for enzymatic calcite precipitation is evaluated. Urea and calcium salt, at various concentrations, are mixed with a concentration-fixed enzyme to obtain the optimal precipitation of CaCO3. The optimally combined solution is injected into sand samples in small PVC cylinders. Then, the improvement in small-scale samples is observed. The combination, approved for small-scale tests, is further used for larger-scale tests. The porosity distribution within the soil is evaluated by sampling the treated sand at different locations. A precipitation ratio up to 80% can be obtained using a small amount of the enzyme. The results show that the in situ enzymatic CaCO3 precipitation technique may be feasible for use in larger-scale applications. A multiphysics simulator that considers the calcite precipitation reaction during the transport of the solution is adopted to predict the evolution of the porosity. The predicted porosities are compared with the measured porosities. The results show that the numerical predictions can replicate the actual changes in porosity relatively well and that the numerical model should be helpful in assuming these changes caused by the precipitated CaCO3 induced by the grouting technique examined in this work. © 2013 American Society of Civil Engineers.

DOI： 10.1061/(ASCE)GT.1943-5606.0000959

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

The paper sludge which is generated during paper manufacturing processes is incinerated to reduce its volume, and then the paper sludge ash is produced. The greater part of the paper sludge ash has been disposed to landfills and an effective utilization of the paper sludge ash has not been promoted. From view point of the effective utilization of industrial wastes, the authors have proposed that the granulated materials made of the paper sludge ash are used for concrete aggregate and evaluated the applicability of paper sludge ash to concrete. The concrete using the granulated paper sludge ash is lighter, and its water absorption is much higher than those of ordinary concretes. The drying shrinkage strain is larger than that of ordinary concretes.&lt;BR&gt;The lightweight precast materials used for such as forms have a merit of the cost reduction of transportation and construction. In this study, the applicability of the mortar using granulated paper sludge ash for aggregate (PS mortar) to precast lining form is examined. Firstly, the flowability and the strength of the PS mortar are examined and the curing performance of the PS mortar form is indirectly evaluated by measuring strength and air tightness of back filling concrete. Secondly, the drying shrinkage of the PS mortar is measured and its prediction equation is proposed. Finally, Practicality of the PS mortar to precast materials is evaluated by observing deformation and crack occurring of the precast PS mortar walls constructed tentatively in this study. From results of the above examinations, it is found that the PS mortar form has a high curing performance. However, the PS mortar may not be unconditionally utilized because its drying shrinkage strain is relatively large.

DOI： 10.2473/journalofmmij.128.611

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

There are many paper mills in the eastern area of Ehime Prefecture where the pulp and paper industry has been well developed. Paper sludge containing large amounts of water is generated during paper manufacturing processes. The paper sludge is incinerated to reduce its volume, and then the paper sludge ash is produced. The greater part of the paper sludge ash has been disposed to landfills and an effective utilization of the paper sludge ash has not been promoted. Due to environmental policy and regulations in Japan, it will become difficult to obtain supplies of river sand and sea-bed sand which have been used for concrete aggregate. On the other hand, demands for the effective utilization of industrial wastes for construction materials that are typically made of natural resources will rise in future. From this background, the authors propose an effective utilization of granulated paper sludge ash produced from the paper mills as concrete aggregate.&lt;BR&gt;In this study, the applicability of granulated materials made of the paper sludge ash to concrete aggregate is evaluated by carrying out the following experiments. Firstly, the physical and chemical properties of the paper sludge ash are evaluated and a mixture proportion of the granulated paper sludge ash is examined through its strength measured by point load tests. Secondly, Particle size distribution, density, water absorption rate, and solid content of the granulated paper sludge ash are evaluated from the view point of concrete aggregate. Finally, durability, mechanical and physical properties of concretes mixed with the granulated paper sludge ash used as proxy of sand aggregate are also evaluated. From results of the above experiments, it is found that the concrete using the granulated paper sludge ash is lighter, and its water absorption is much higher than those of ordinary concretes. The strength can satisfy the requisite for design standards of reinforced concretes. The drying shrinkage strain is larger and the air tightness is lower than those of ordinary concretes.

DOI： 10.2473/journalofmmij.128.576

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

From the viewpoints of multiple-utilization of land, environmental safeguards, energy conservation, etc, a temporary storage of hot water in openings excavated in rock may be worthwhile. In this case, the rock mass around the openings will respond by coupled thermo-mechanical effects induced by the hot water.&lt;BR&gt;In this study, flow-through experiments on a single fracture in granite has been carried out under confining pressures of 5-10 MPa, and at temperatures of 20-90°C. The fracture aperture and the permeability monotonically decreased with time at room temperature, and reached a quasi-steady state. Then, after the temperature was raised to 90°C, the aperture decreased again throughout the rest of the experiments. Fluid samples were taken from the outlet to examine the elemental concentrations that were evaluated by inductively-coupled plasma atomic emission spectrometry (ICP-AES) . The elemental concentrations increased with increase of temperature. After the flow-through experiments, the fracture surface was observed by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) . The formation of a few kinds of precipitated minerals such as silica and calcite was revealed. The precipitation was limited to quite local and small areas. However, the precipitated minerals seemed to have had some influences on the permeability.

DOI： 10.2473/journalofmmij.128.72

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

When considering a geological isolation of high level radioactive wastes, the evolutions of the mechanical, hydraulic, and transport properties of the targeted rocks should be evaluated in advance because those may be degraded by the coupled thermal, hydraulic, mechanical, and chemical effects induced by the emplacement of the wastes. Chemical reactions such as mineral dissolution and precipitation that is dependent on temperature and pH conditions, may be one of the key issues that may trigger off the degradation. Therefore, the dissolution mechanism of the targeted rocks should be thoroughly examined under various temperature and pH conditions.&lt;BR&gt;In this work, a suit of flow-through experiments in granite has been conducted at temperatures of 30, 50, and 70°C, and at pHs of 6, 9, and13, to examine the granite dissolution behavior. An apparent dissolution rate equation of the granite is defined under arbitrary temperature and pH conditions. The acquired dissolution rates are compatible to those evaluated in the literature. Utilizing the dissolution rates, the evolution of the element concentrations measured in the permeability experiments on the granite fracture is replicated. The predicted concentrations follow the experimental measurements both qualitatively and quantitatively. Although showing in a good agreement with the experimental measurements, the predictions slightly underestimate the actual. This is attributed likely to the unaccounted effects of mineral dissolution at the contacting asperities, indicating that a more sophisticated dissolution equation should be achieved by considering such a dissolution mechanism.

DOI： 10.2473/journalofmmij.128.79

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Society for Rock Mechanics  

In this study, a series of permeability experiments on both intact rock and a single fracture in sandstone and on a single fracture in siliceous mudstone has been conducted under confining pressures of 3 – 15 MPa, and at temperatures of 20 – 90 °C for several hundred days in each experiment. Spontaneous alteration of permeability and dissolved mass fluxes have been observed. In sandstone, the permeability of intact rocks little changed until a couple of hundred days, then it started to increase with time. In mudstone, the permeability in a single fracture monotonically decreased with time and reached a quasi-steady state within one month. However, it started to increase with time after ~100 days. This augmentation in the permeability in sandstone and mudstone should be attributed to mineral dissolution within the void spaces. In contrast with the sandstone results, the fracture permeability in mudstone resumed decreasing with time throughout the rest of the experiment. A coupled chemomechano conceptual model, accounting for pressure and free-face dissolutions, is utilizedto follow the evolution of the permeability observed in the experiments. The model predictions show a relatively fair agreement with the experimental measurements, although further considerations and modifications are found to be required.

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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)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Examining the evolution of fracture permeability under stressed and temperature-elevated conditions, a series of flow-through experiments on a single rock fracture in granite has been conducted under confining pressures of 5 and 10 MPa, under differential water pressures ranging from 0.04 to 0.5 MPa, and at temperatures of 20-90 degrees C, for several hundred hours in each experiment. Measurements of fluid and dissolved mass fluxes, and post-experimental microscopy, were conducted to constrain the progress of mineral dissolution and/or precipitation and to examine its effect on transport properties. Generally, the fracture aperture monotonically decreased with time at room temperature, and reached a steady state in relatively short periods (i.e., &lt;400 h). However, once the temperature was elevated to 90 degrees C, the aperture resumed decreasing and kept decreasing throughout the rest of the experimental periods. This reduction may result from the removal of the mineral mass from the bridging asperities within the fracture. Post-experimental observations by scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy (SEM-EDX), revealed the formation of several kinds of secondary minerals such as silica and calcite. However, the precipitated minerals seemed to have had little influence on the flow characteristics within the fracture, because the precipitation was limited to quite local and small areas. The evolving rates and ultimate magnitudes of the fracture aperture are likely to be controlled by the stress exerted over the contacting asperities and temperatures, and by the prescribed flow conditions. Thus, this complex behavior should be attributed to the coupled chemically-and mechanically-induced effect. A coupled chemo-mechano conceptual model, accounting for pressure and free-face dissolutions, is presented in this paper to follow the evolution of the fracture permeability observed in the flow-through experiments. This model addresses the two dissolution processes at the contacting asperities and the free walls within the fractures, and is also capable of describing multi-mineral dissolution behavior. The model shows that the evolution of a fracture aperture (or related permeability) and of element concentrations may be followed with time under arbitrary temperature and pressure conditions. The model predictions for the evolving fracture aperture and elements concentrations show a relatively good agreement with the experimental measurements, although it is not possible to replicate the abrupt reduction observed in the early periods of the experiments, which is likely to be due to an unaccounted mechanism of more stress-mediated fracture compaction driven by the fracturing of the propping asperities. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.apgeochem.2011.07.005

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASCE-AMER SOC CIVIL ENGINEERS  

The temporary storage of hot water in openings excavated in rock may be worthwhile for multiple land-use applications, environmental safeguards, and energy conservation. When used for hot water storage, the rock mass around the openings will respond by coupled thermomechanical effects induced by the hot water. In this study, a submergence test of granite and sandstone at 20 and 95 degrees C was used to examine the thermal behavior of the rock mass around the openings to obtain the mechanical properties of uniaxial compressive strength and elastic modulus. A uniaxial compression creep test of the rock at high temperatures was also performed and calculations with various constants for the creep were examined. With the results obtained in this work, the temperature and stress distribution around the openings when hot water is stored was analyzed by considering the creep properties. The thermal behavior and stability of the openings were also examined. The displacement of the openings was predicted to be approximately 2% of the diameter after 1,000 days. (C) 2011 American Society of Civil Engineers.

DOI： 10.1061/(ASCE)GM.1943-5622.0000063

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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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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

A conceptual model, accounting for pressure and free-face dissolutions, is presented to follow the evolution of fracture permeability in granite that was observed in a flow-through experiment. This model addresses the two dissolution processes at contacting asperities and free walls within fractures, and also describes the multi-mineral dissolution behavior, showing a capability that the evolution of fracture aperture (or related permeability) may be followed with time under an arbitrary temperature and pressure conditions. Predictions utilizing the model proposed in this study show a relatively good agreement with the experimental measurements, although the concentrations predicted underestimate the actual.

DOI： 10.2208/jscejc.65.41

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

It is quite important to mine ores with forming a stable retaining wall from the viewpoints of the safety for miners and the scenic preservation of the mine. However, there have been always a lot of the collapse of retaining wall. Four collapses in 2004, one in 2005 and two in 2006 occurred in the Shikoku, Japan. Therefore, the Shikoku branch of Chugoku Shikoku industry. safety and inspection department established a technical committee in the Chugoku Shikoku mine safety committee in 2005 and 2006. The technical committee summarized the present status of the retaining wall in Shikoku. From the summarized materials, all cases of the collapse of retaining wall were investigated. Moreover, they were reviewed and considered from the viewpoints of cause, foresight and provision.

DOI： 10.2208/jscejc.64.57

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

A conceptual model is presented to follow the evolution of permeability in siliceous rocks mediated by pressure solution. Specifically, the main minerals of siliceous rocks that are quartz, cristobalite, and amorphous silica, are focused to examine differences of the permeability evolutions among them at effective pressures of 1, 5, and 10 MPa, and temperatures of 20 and 90 °C. The rates and magnitudes of permeability reduction increase with increases of the pressures and temperatures applied. Ultimate permeabilities reduced by the order of 90 % at the completion of dissolution-mediated compaction at 10 MPa and 90 °C. Precipitation may augment more degradation of flow transport in time.

DOI： 10.2208/jscejc.63.1091

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The authors have proposed and discussed temporary storage of heated water in openings excavated in rock moun-tain from the viewpoints of multiple-utilization of land, environmental safeguards, energy conservation, etc. When used for heated-water storage, the rock mass around the openings will receive the effects of the heated water. In this study, for obtaining physical properties used for analysis of thermal behavior of rock mass around openings, the effect of the difference between Wet (the water-retaining condition) and Dry and physical properties on strength, deformation characteristics and thermal properties at high temperatures were examined using 5 kinds of rock (granite, andesite, sandstone, tuff and mudstone). In addition, a uniaxial compression creep test at high temperatures of the rock was also carried out, then compared with the creep property at room temperature. The calculation of various constants on the creep was tried using Burgers model. In outline, the results show the strength of Wet rock is smaller than that of Dry, and strength lowers with the rise in the temperature, the lowering proportion being larger in Wet. The elastic modulus of tuff and mudstone are smaller than those of granite, andesite and sandstone. In particular, the lowering proportion at high temperatures is also large in Wet. Thermal property can be considered almost constant for practical use, and the effect of the temperature is small. As the difference of Dry and Wet is large, it seems that the effect of pore water is large. Especially, the tendency is remarkable in tuff and mudstone in which porosity is large. Temperature influences the uniaxial compression creep property of rock.

DOI： 10.2472/jsms.55.489

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

As one of the quiet rock fracture methods, a slide-type hydraulic rock fracture machine was made on a trial basis. This machine was able to add a concentrated load in the pressure hole using a wedge in four directions perpendicularly for obtaining an effective fracture.<br>Using this machine, the effect of empty holes and size of pressure plate on rock fracture was investigated by theoretical analysis, laboratory and field tests. Results of the investigations showed that empty holes are effective to reduce the force required for fracture. It was also found that the force and energy required for fracture decrease with increasing size of the pressure plate.

DOI： 10.2208/jscej.2004.771_147

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Society of Materials Science Japan  

When high and low temperature materials, such as heated water, LNG, LPG and frozen food etc. actually are stored temporally in openings excavated in rock mountain, as the quantity of these changes continually, the rock mass around openings will receive the effects of thermal hysteresis of high and low temperatures. Therefore, obtaining the strength and deformation characteristics of rocks after receiving thermal hysteresis becomes important for discussing the stability of the openings. In this study, these characteristics of rocks were examined. From the results of the tests, it was found that strength and deformation characteristics of rocks decrease with the increasing amount of thermal hysteresis. However, the ratio of the decrease also decreases. From these facts, it is supposed that the strength and deformation characteristics of rocks will converge to a constant value. Then using the results of the tests, thermal behavior of rock mass around openings were analyzed and discussed.

DOI： 10.2472/jsms.51.333

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Mining and Materials Processing Institute of Japan  

Artificial rocks have been often used in aquariums, zoos, botanical gardens and parks etc. However, recently, opportunity to use the artificial rocks on surfaces of various structures is increasing. This probably comes from the reason that using the artificial rocks is effective from a view point of balancing with environment, so demand of them is expected to increase in near future. To meet the demand, it is desired to clarify strength, deformability and thermal properties of artificial rocks. In this study, these properties for two types of artificial rocks at high and low temperatures and effects if thermal hysteresis on them were examined. The results indicated that the artificial rocks are able to be used on the surfaces on structures exposed to temperature change in wide variety of natural environment.

DOI： 10.2473/shigentosozai.116.13

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Soc Mater Sci, Japan  

The authors have been proposed and discussed temporary storage of high and low temperature materials in openings excavated in rock mountain. Here, high temperature materials means such as heated water which is produced by surplus heat from garbage burning plants, while low temperature materials means such as LNG, LPG, frozen food etc. In this case, as the storage quantity of heated water, LNG and LPG will change with these use continually, rock masses around openings to store these materials will receive effects of thermal hysteresis of high and low temperatures. Therefore, obtaining the strength and deformation characteristics of rock affected by the thermal hysteresis becomes important for discussing the stability of the openings. In this study, strength and deformation characteristics of granite and tuff were examined after undergoing thermal hysteresis of high and low temperatures. From the results, it was found that the decreasing ratio of strength and deformation of rocks decrease with the increasing number of thermal hysteresis, and it is supposed that the value will converge to a constant value.

DOI： 10.2472/jsms.48.334

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

The authors have proposed temporary storage of heated water in openings excavated in rock mountain. In this case, countermeasures for the reduction of thermal stress around openings and preventing leakage of heated water from openings become important. In this study, the authors proposed the reduction of thermal stress by using adiabatical material, resin lining system and combination lining system of resin and adiabatical material as a countermeasure for preventing leakage and reduction of thermal stress. The results of the test of physical properties of adiabatical material and resin at high temperature are described. And using these values, temperature distribution and stability of openings were analyzed and discussed.

DOI： 10.2208/jscej.1998.610_57

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Strength and deformation characteristics of rock which has low porosity and high porosity were examined after undergoing thermal hysteresis of high and low temperatures using a thermal cycle apparatus. From the results, it was found that temperature, the number of hysteresis and porosity, etc. were important factors which have an influence on strength and deformation characteristics.

DOI： 10.1016/S1365-1609(97)00048-8

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

The thermal behavior of rock mass around openings when low temperature material are stored, will be different with each type of rock. In this study, Affect of the difference of water content in each rock on physical properties in wet state under low temperature were investigated by experiment. From results, it was found that the physical properties of rocks which have large porosity, were affected by pore water. Then, temperature distribution and behavior around openings were analyzed and the results which were discussed for mechanism of crack development are described. In the case of granite and sandstone, it was found that cracks were caused by tensile stress. On the other hand, in the case of tuff and mudstone, cracks were caused by shearing stress.

DOI： 10.2208/jscej.1996.547_211

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

For the purpose of improving the quality of life and saving enagy, heated water produced by using surplus heat from garbage-burning plant etc., will be utilized well in the near future for many purposes. To insure a stable supply, temporary storage in rock mass openings in mountain may become an important problem. In this study, stability and leakage of openings were estimated by analysis using the physical properties of rock which were obtained by experiment.

DOI： 10.2208/jscej.1990.424_227

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Copyright 2018 ARMA. We developed a coupled thermal-hydraulic-mechanical-chemical (THMC) simulator, iPSACC (interface for Pressure Solution Analysis under Coupled Conditions) that can consider the coupled processes including change of physical properties of the rocks due to the cracking by incorporating elastic damage theory. Especially, modeling the relationships between geochemical reactions such as pressure solution within rock fracture and rock damage is most important characteristic of this simulator. By using the developed simulator, long-term prediction of rock permeability was conducted by assuming subsurface environment near the radioactive waste repository. The predictions show that in EDZ many fractures occur near the disposal cavity and permeability increases in damaged zone during the excavation, and after excavation the permeability of the damaged zone decreases with time due to pressure solution at contacting asperities within fractures. It is concluded that pressure solution within the fractures has significant impact on the change of the permeability in EDZ area by cavity excavation.

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© 2017 ARMA, American Rock Mechanics Association. We improved our thermal-hydraulic-mechanical-chemical (THMC) simulator to predict the long-term permeability change of the fractured rocks. The model evaluates the influence of the geochemical reaction on the evolution of the permeability in fractured rocks by considering pressure solution in detail. Pressure solution that occurs at both grain contacts and contacting asperities within fractures was incorporated in the model. By using the developed THMC numerical model, long-term prediction of rock permeability was conducted by replicating the subsurface environment near the radioactive waste repository. As a result of the analyses, the permeability decrease by two orders of magnitude smaller than the initial value occurs due to pressure solution at contacting asperities within fractures in the EDZ area. In carrying out radioactive waste disposal, it is apparent that pressure solution within the fractures has significant impact on minimizing the increase of the permeability in EDZ area.

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Copyright 2016 ARMA American Rock Mechanics Association. A coupled thermos-hydro-mechanical-chemical (THMC) numerical model is presented to predict the long-term change in permeability of the porous rocks that are composed purely of quartz. Especially, the chemo-mechanical process of the pressure dissolution is explicitly taken into account in the model. By simulating the burial of high-level radioactive wastes in the deep subsurface (i.e., by applying the simulated confining pressure and temperature conditions), the long-term evolution of the rock permeability was predicted using the model. The predictions obtained a significant influence of the pressure dissolution on the change in permeability with time. The predicted permeability of the rocks close to the wastes decreased by roughly one order of magnitude in 104 years when considering the pressure dissolution, while the permeability changed little during the same period when the pressure dissolution was not considered. The reduction should delay the transportation of the radioactive materials.

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This paper discusses the experimental and numerical work on Enzyme Mediated Calcite Precipitation, EMCP, technique along with the improved mechanical properties of sand achieved by employing this technique. The homogenous sand specimen having a diameter of 57 cm and a height of 60 cm is prepared inside a steel drum. Freshly prepared grout solution (urea-CaCl2 and urease) is injected at the centre of the sand specimen. Afterwards, the improved samples within the treated specimen is taken and subjected to the compressive strength tests. The calcite distribution throughout the specimen is also evaluated. A multi-component, fluid flow and geo-chemical transport simulator that can incorporate the precipitation reaction during the flow, is used to predict the calcite distribution. The experimental results are compared with the numerical predictions. The evaluated simulator can approximately predict the distribution of calcite within the sand specimen. The small amount of calcite precipitated within the soil mass appreciably improves the mechanical properties of sandy soil. The improved mechanical properties are enough to increase the resistance of soil against liquefaction.

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Copyright (2014) ARMA, American Rock Mechanics Association In this study, evolution of mechanical and hydraulic properties in Berea sandstone with initial porosity of 20 % is examined quantitatively by replicating mineral trapping process within pore spaces. The artificially accelerated mineral trapping is achieved by injecting a grout, resulting in calcite precipitation. The amount of calcite precipitated can be controlled by changing the concentrations of the grout and the total injection volume. The preliminary experiments indicate that the change of the mechanical and hydraulic properties is significant even if the calcite amount is relatively small - The values of Young&#039;s modulus/permeability increase/decrease with increase of the calcite amount. Specifically, the permeability decreases by one order of magnitude as the initial porosity of 20 % reduces to 18 %. This intense decrease of permeability may not be able to be replicated by existing numerical models, although distribution of the calcite precipitated within rock samples should be adequately examined because uniform distribution may not be achieved.

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A series of long-term permeability experiments using Berea Sandstone and Horonobe Mudstone has been conducted so as to understand the evolution of rock permeability under stressed and temperature-elevated conditions. The well-controlled experiments are carried out at confining pressures of 3.0-15 MPa and temperatures of 20 or 25 and 90°C. Flow-through experiments are conducted regularly (i.e., 5 or 10 day interval) to examine the evolution of rock permeability throughout the experiments - it should be noted that each experiment is kept always more than 500 days. Effluent concentrations are also measured for the ten elements of Si, Al, K, Fe, Ca, Na, Mg, Ti, S, and Cl that are included mainly in the targeted rocks. Rock samples were prepared for a SEM-EDX and/or a micro-focus X-ray CT to observe its microstructure. The SEM-EDX observation revealed that mineral dissolution dominates over mineral precipitation, and the micro-focus X-ray CT observation shows a slight increase in pore volume for the sandstone sample that has experienced long-term confining pressure and temperature. Copyright 2013 ARMA, American Rock Mechanics Association.

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Publisher：John Wiley & Sons, Inc.  

DOI： 10.1002/9781118623565.ch46

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A suite of permeability experiments on intact rocks in sandstone and on a single fracture in siliceous mudstone has been conducted under confining pressures of 3-15 MPa, and at temperatures of 20-90°C for several hundred days in each experiment. For the mudstone experiments, oil-flow experiments are also conducted to examine the effect of mineral dissolution on the flow behavior - the oil-saturated condition refrains from the mineral dissolution and enables to certify if mechanical creep occurs under the stressed conditions. Evolution in permeability and dissolved mass fluxes were periodically measured to examine the flow behavior under stress and temperature conditions. In sandstone, the permeability of intact rocks little changed until a couple of hundred days, then started to increase with time. In mudstone, the permeability in a single fracture monotonically decreased with time and reached a quasi-steady state within one month. However, it started to increase with time after ?100 days. This augmentation in the permeability in sandstone and mudstone should be attributed to mineral dissolution within void spaces. Copyright 2012 ARMA, American Rock Mechanics Association.

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Language：English   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

A suite of flow-through experiments in granite fracture is conducted under various temperature, confining pressure, and pH conditions, to examine the evolution of the fracture permeability. The well-controlled experiments are carried out at temperatures of 25 and 90 degrees C, confining pressures of 5 and 10MPa, and pH's of 7 and 11. At 25 degrees C, generally, the fracture permeability decreases with time and reaches a quasi-steady state within a few hundred hours. However, after the temperature is raised to 90 degrees C, the permeability again resumed decreasing throughout the rest of the experimental periods. The higher temperature, confining pressure, and pH are prescribed, the faster evolutions of the fracture permeability are observed. These results may indicate that the near-field rock mass of HLW may become safer with time in terms of solute transport behavior.

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Language：Japanese   Publisher：日本技術士会四国支部  

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A suite of flow-through experiments in granite fracture is conducted under various temperature, confining pressure, and pH conditions, to examine the evolution of the fracture permeability. The well-controlled experiments are carried out at temperatures of 25 and 90 degrees C, confining pressures of 5 and 10MPa, and pH's of 7 and 11. At 25 degrees C, generally, the fracture permeability decreases with time and reaches a quasi-steady state within a few hundred hours. However, after the temperature is raised to 90 degrees C, the permeability again resumed decreasing throughout the rest of the experimental periods. The higher temperature, confining pressure, and pH are prescribed, the faster evolutions of the fracture permeability are observed. These results may indicate that the near-field rock mass of HLW may become safer with time in terms of solute transport behavior.

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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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A series of stirred-flow-through experiments using granite powder has been conduced under temperature and pH conditions controlled so as to evaluate the dissolution kinetics of the Mizunami granite. The well-controlled experiments are carried out at temperatures of 30-70°C, and pH 6-13, and a constant flow rate of the permeant fluid is set to be 0.1 mL/min. The system likely reaches a quasi-steady state roughly 100 hrs after the experiments get started. Effluent concentrations are measured by regular sampling for the seven elements of Si, Al, K, Fe, Ca, Na, and Mg that are included mainly in the targeted rock. Relatively high concentrations of Si, K and Ca are observed throughout the experiment. Generically, the higher temperature and pH are prescribed, the faster dissolution rates are evaluated. Subsequently, dissolution rate constants of the granite itself are evaluated using a typical Arrhenius equation and an extended formation taking into account the dependence of pH. Copyright 2010 ARMA, American Rock Mechanics Association.

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DOI： 10.14824/jakoka.2009.0.11.0

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A coupled chemo-mechano conceptual model is presented to follow the evolution of fracture permeability observed in flow-through experiments in a single rock fracture in granite. The experiments are conducted under constant confining pressures of 5 and 10 MPa with differential water pressures ranging 0.01-0.5 MPa, and temperatures of 20 and 90°C. Permeability measured shows a monotonic decrease with time, via apparent steady state after relatively short periods at 20°C. A presented model addresses the two dissolution processes at contacting asperities and free walls within fractures, and also describes the multimineral dissolution behavior, showing a capability that the evolution of fracture aperture (or related permeability) may be followed with time under an arbitrary temperature and pressure conditions. Predictions utilizing the model proposed in this study show a relatively good agreement with the experimental measurements, although an abrupt reduction observed is incapable of being replicated, that is due to an unaccounted effect in the current model. Copyright 2009 ARMA, American Rock Mechanics Association.

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The authors have proposed and discussed temporary storage of heated water in openings excavated in rock mountain from the viewpoints of multiple-utilization of land, environmental safeguards, energy conservation, etc. When used for heated-water storage, the rock mass around the openings will receive the effects of the heated water. In this study, a uniaxial compression creep test at high temperatures of the rock was also carried out, then the calculation of various constants on the creep was tried. Using the results obtained in this work, temperature and stress distribution around the openings when heated water were stored was analyzed by considering the creep properties. The thermal behavior and stability of the openings were also examined. The displacement of the openings was predicted to be 1.96 % of the diameter after one thousand days.

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In this study, the development of adiabatical material using the industrial waste such as paper sludge incineration ash, crushed stone sludge, iron slag and gypsum was tried. That is the thermal insulation performance was examined. And, the case in which the vacuum was used jointly was also examined. Then, the development of insulator was tried. The soundproofing performance was also examined and discussed.

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Other Link： http://iyokan.lib.ehime-u.ac.jp/dspace/handle/iyokan/1472

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The large paper sludge is discharged from the paper industry which is key industry in the Toyo district in Ehime Prefecture. However, the recycling rate of the paper sludge is low. The paper sludge is utilized as a usual combustion aid material. Most is disposed in ground the paper sludge incineration ash. It gropes for the utility value of incinerated ash. The part has already been used as an improved material for earth worker, and in search of further value added, the examination begins to have been made at present In this study, from the background like the above, the development of adiabatical material using the paper sludge incineration ash was tried. To begin with, the granular sample was produced experimentally by the granulator by the agitation granulation system in respect of the paper sludge ash. Next, adiabatical material was produced experimentally using the granulation sample, and the thermal insulation performance was examined. And, the case in which the vacuum was used jointly was also examined.

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When heated water is stored in openings excavated in rock mass, the rock mass around openings will receive the affect of high temperatures. From the results of the previous research, it is found that non-steady heat conduction and thermal stress occurred in the rock mass. Therefore evaluation of the temperature distribution around openings becomes one of the important problems for the stability of openings. In the case that heated water is stored in the opening, the convection is generated in the heated water and the distribution of temperature in the openings is not a general phenomenon. In this study, temperature distribution around openings when heated water was stored was analyzed considering convection of the heated water and discussed. From the results of the analysis, it is supposed that the convection of heated water affects on the temperature distribution around openings.

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The authors have proposed and discussed temporary storage of heated water in caverns excavated in rock mountains. In this case, the rock mass around caverns will receive the affects of high temperatures due to the storage of heated water. From the results of previous research, it was found that non-steady heat conduction and thermal stress occurred in the rock mass around caverns. Therefore, the evaluation of the temperature distribution around caverns is one of the important problems for the stability of caverns. In this study, temperature distribution around caverns when heated water was stored was analyzed considering convection of the heated water. From the results of the analysis, it was supposed that the convection of heated water affects the temperature distribution around caverns. Then using the results of the temperature analysis, the thermal stress distribution was analyzed and the stability of the caverns was discussed.

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When low temperature materials such as LNG, LPG and frozen food, are stored in rock caverns excavated in mountain, rock mass around caverns is received effect of low temperatures. Therefore, it is necessary for behavior analysis of rock cavern to obtain strength, deformation characteristics and thermal properties of rocks at low temperatures. Their properties for thermal behavior analysis were obtained by the tests at low temperatures. Then using these value, temperature and stress distribution around rock caverns were analyzed by Finite Divided Element Method and Crack Analysis Method which have been proposed by the authors. From the result of the analysis, thermal behavior of rock mass around caverns was discussed.

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The authors have proposed and discussed temporary storage of heated water in openings excavated in rock mountains. Heated water, produced by surplus heat from garbage burning plants, should be used for many purposes such as district heating heated water supply, green houses, etc. In this case, the rock mass around openings will receive the affect of thermal hysteresis of high temperatures as the storage quantity of heated water continually changes according to its use. In this study, strength and deformation characteristics of some types of rocks were examined after receiving thermal hysteresis of high temperatures. The effects of the amount of thermal hysteresis, atmospheric temperature, porosity, etc, on strength and deformation characteristics of rocks were discussed. The results of the tests mentioned above were used for analyzing temperature and stress distribution around openings by using the Finite Divided Element Method and FEM. Then the effect of thermal hysteresis of high temperatures on thermal behavior of some types of rock mass around openings was discussed.

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The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. In this case, as the rock mass around the openings will receive thermal hysteresis of low temperatures, it is necessary to obtain strength and deformation characteristics of rocks undergoing thermal hysteresis of low temperatures to consider the thermal behavior of rock mass around openings and the stability of openings. In this study, strength and deformation characteristics of some types of rocks were examined after undergoing thermal hysteresis of low temperatures. Then using the results of the tests, thermal behavior of the rock mass around openings was analyzed and discussed. From the results of analysis, it was found that in the case of undergoing thermal hysteresis, length of cracks and freezing zone were almost same as in the case of not undergoing thermal hysteresis.

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The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. In this case, as the rock mass around the openings will receive effects of low temperature, it is necessary to consider the thermal behavior and the stability of openings. In this study, strength and deformation characteristics obtained by the uniaxial tension test and by the compression test at low temperatures were discussed. Using the results of the test, temperature and stress distribution around openings when LNG was stored within, were analyzed. Then thermal behavior of the rock mass around openings was analyzed and discussed.

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The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. In this study, strength and deformation of some types of rocks were examined after receiving thermal hysteresis of low temperatures. The effects of the amount of thermal hysteresis, temperature range, porosity, etc, on strength and deformation of rocks were discussed. Using the results of the tests, temperature and stress distribution around openings were analyzed. Then the effect of thermal hysteresis of low temperatures on thermal behavior of the rock mass around openings was discussed.

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The demand for LNG and LPG have tended to increase in Japan. Frozen food also shows a similar tendency. With these points as background, it is expected there will be an increase in the need for storage establishments in the near future. The authors have proposed and discussed temporary storage of low temperature materials in openings excavated in rock mountains. In this case, the rock mass around the openings will receive thermal hysteresis of low temperatures. For this, it is necessary to obtain strength and deformation characteristics of rocks affected by thermal hysteresis to consider the thermal behavior of rock mass around openings and the stability of openings. In this study, some of these types of rocks were examined after receiving thermal hysteresis of the range between room temperature and -160 degrees C. The effects of range and amount of thermal hysteresis, atmospheric temperature, etc. were discussed. Then, using the results of the experiments, for the case where LNG will be stored in openings, temperature acid stress distribution around openings were analyzed. Then the effect of thermal hysteresis of low temperatures on thermal behavior of the rock mass around openings was discussed.

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The authors have proposed and discussed temporary storage of low temperature materials such as LNG, LPG and frozen food in openings excavated in rock mountains. In this case, as the rock mass around the openings will receive thermal hysteresis of low temperatures, it is necessary to obtain strength and deformation characteristics of rocks undergoing thermal hysteresis of low temperatures to consider the thermal behavior of rock mass around openings and the stability of openings. In this study, strength and deformation characteristics of some types of rocks were examined after undergoing thermal hysteresis of low temperatures. Using the results of the experiments, temperature and stress distribution around openings were analyzed. From the results of analysis, it was found that in the case of undergoing thermal hysteresis, crack length and freezing zone are about same as in the case of not undergoing thermal hysteresis.

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To prevent the problem of noise and vibration which occurs in rock excavation work using explosives or machinery, a hydraulic fracture machine has been made on a trial basis. The machine was able to add a concentrated load in the pressure hole by a wedge in four directions perpendicularly for obtaining an effective fracture. Cement mortar was used as a homogeneous specimen, the fracture experiment was carried out using two types of machines. Then, the effective distance between the pressure hole and the empty hole was investigated by a field test. The effect of the wedge was investigated by an experiment. Using the results of the experiment, mechanical behavior around the pressure hole and the development of the cracks were simulated by using "Crack Analysis Method". Then, the results were compared with the results of the field tests and discussed.

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The authors propose a "resin lining system" as a countermeasure for preventing leakage of gas and liquid in case of low temperature materials storage in openings excavated in rock mountain. On the other hand, to reduce thermal stress around the openings, the authors propose to use adiabatical materials. Then, a "combination lining system of resin and adiabatical material" are also proposed as a countermeasure for preventing leakage of gas and liquid from openings and reduction of thermal stress at the same time.

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When low temperature materials such as LNG, LPG and frozen food, actually are stored in openings excavated in rock mountain, as the quantity of LNG and LPG change continually, the rock mass around openings will receive the effects of thermal hysteresis of low temperatures. Therefore, obtaining the strength and deformation characteristics of rocks after undergoing thermal hysteresis of low temperatures becomes important for discussing the stability of the openings. In this study, strength and deformation characteristics of rocks which had undergone thermal hysteresis of low temperatures were investigated. Using these values, stress distribution around openings were analyzed theoretically, and the affect of thermal hysteresis of low temperatures on cracks and the cracked zone around openings are discussed. Then, countermeasures for preventing leakage of gas and liquid from openings and reduction of thermal stress around openings are also discussed.

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The authors have proposed temporary storage of heated water in openings excavated in rock mountain. In this case, the rock mass around openings will receive the effects of thermal hysteresis of high temperatures. In this study, strength and deformation characteristics of rocks were examined at high temperatures and after undergoing thermal hysteresis of high temperatures by using a thermal cycle apparatus. From the results, it was found that temperature, number of cycles and porosity etc, were the most important factors which have an influence on strength and deformation characteristics. Using these values, stress distribution around openings was analyzed theoretically, and the affect of thermal hysteresis of high temperatures on rock mass around openings for storage of heated water was discussed.

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