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Natural Hazards, 2014
Your article is published under the Creative Commons Attribution license which allows users to re... more Your article is published under the Creative Commons Attribution license which allows users to read, copy, distribute and make derivative works, as long as the author of the original work is cited. You may selfarchive this article on your own website, an institutional repository or funder's repository and make it publicly available immediately.
Marine Georesources & Geotechnology, 2016
Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No... more Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No. 1 nuclear power plant is an urgent requirement. The purpose of this study was to develop a sealing material which can be used as an engineered barrier for a final disposal facility for the soils and wastes contaminated by radioactive cesium. The analyses conducted based on 4-m-thick sealing layer revealed that the hydraulic conductivity of the sealing material needs to be kept below 5.0 � 10 À 10 m/s to avoid the seepage of contaminants below the environmentally safe limits. Sealing material was developed using marine clay-bentonite mixture and the engineering characteristics were examined. The results of laboratory experiments showed that, with the addition of bentonite, the hydraulic conductivity equal to or less than 5.0 � 10 À 10 m/s was achieved when the effective consolidation stress is equal to or more than 27 kPa. From the tests for adsorption properties for cesium, it was found that the sealing material showed the significant capacity of adsorption for cesium in seawater. It was concluded that the construction of waste disposal facility on the sandy seafloor is feasible using the sealing layer proposed in this study.
SOILS AND FOUNDATIONS, 2011
Lecture Notes in Civil Engineering
Geotechnical Engineering for Disaster Mitigation and Rehabilitation, 2008
Shallow slope failures, induced by torrential rainfall, are common in the western Japan, where Ma... more Shallow slope failures, induced by torrential rainfall, are common in the western Japan, where Masado, a regional soil made of decomposed granite, is widely distributed in natural slopes. There is quite a few information on the geotechnical conditions, because of the difficulty of ground investigation on steep slopes with lush vegetation. The lightweight dynamic cone penetration test (LWDCPT) has been
Doboku Gakkai Ronbunshuu C, 2007
Slope failures caused by rainfall on weathered granite are common occurrences in many parts of th... more Slope failures caused by rainfall on weathered granite are common occurrences in many parts of the world and it is more severe in Japan where there are a significant number of slopes susceptible to failure. At present, about 31,987 natural, and valley slopes are found to be susceptible to landslide disasters in Hiroshima Prefecture, the highest number of any prefecture in Japan. In Hiroshima Prefecture, the prefectural land is divided into 350 units of 5 km 2 , and the hazard of each unit was assessed based on the rainfall data and past records of failures. However, the existing hazard assessment system was found not to be adequate of making better predictions of individual failures in the region, and moreover the system was developed without carrying out any reliable slope stability analyses. In this study, an attempt has been made to understand the mechanism of individual slope failure through seepage analyses and stability analyses. A series of laboratory model tests were conducted to develop the relationships among volumetric water content, degree of saturation, suction, and coefficient of hydraulic conductivity under unsaturated conditions. Field investigation and laboratory tests were conducted based on the four valleys which were identified as potentially hazardous zones in Higashi-Hiroshima city in Hiroshima Prefecture. Graphical relationships were developed among the volumetric water content, suction, rainfall intensity, coefficient of hydraulic conductivity, and degree of saturation for Masado soils. Based on the relationships developed, suction was calculated along the soil profile of natural valleys with the lapse of time. Thus, shear strength parameters were determined based on the degree of saturation calculated from the data of volumetric water contents. The stability analyses revealed that the factor of safety gradually decreases with the formation of High Moisture Content Belt (HMCB) and drastically reduces with the formation of the water table. The susceptibility of failure for each of the four valleys is given based on the hazard assessment system, and is compared and discussed.
A major problem in the geotechnical approach to the stability of natural slopes is that there is ... more A major problem in the geotechnical approach to the stability of natural slopes is that there is usually little information on the in-situ geotechnical conditions, because of the extreme di‹culty associated with ground investigations of steep slopes covered with vegetation. In this study, a lightweight dynamic cone penetration test (LWDCPT) has been introduced for a geotechnical survey of natural weathered granitic (Masado) slopes. Based on a series of direct shear tests, the internal friction angle and the apparent cohesion of reconstituted Masado soil were found to be fairly closely related to the void ratio and the degree of saturation in the soil. From the laboratory calibration tests, an equation was created to relate the dynamic cone resistance (q d ) and the void ratio of reconstituted Masado under diŠerent degrees of saturation. Equations were developed to calculate the internal friction angle and the apparent cohesion from the value of qd for Masado at a known degree of saturation. LWDCPT and direct shear tests were carried out on undisturbed samples taken from a natural Masado slope. The estimated internal friction angle and the apparent cohesion calculated with the value of qd in the LWDCPTs agreed fairly well with those of tests on the undisturbed samples obtained in laboratory shear tests.
![Research paper thumbnail of Erratum to “Practical slip circle method of slices for calculation of bearing capacity factors” [Soils Found. 54 (6) (2014) 1127–1144]](https://attachments.academia-assets.com/37252340/thumbnails/1.jpg)
](Erratum Erratum to "Practical slip circle method of slices for calculation of bearing capacity fa... more Erratum Erratum to "Practical slip circle method of slices for calculation of bearing capacity factors" [Soils Found. 54 (6) (2014) 1127-1144] Soils and Foundations http://dx.
Soils derived from granitic rocks exhibit a complex degree of variability in space. A grid was es... more Soils derived from granitic rocks exhibit a complex degree of variability in space. A grid was established having 5 m intervals spanning 50 m in length and 20 m in width in order to investigate inherent random heterogeneity of areas covered with weathered granite. Six major patterns of cone resistance varies with the depth were identified. Main grid was further divided at selected locations in 1m grids and at one location in 25 cm grids spanning 1 m in both directions for better understanding of spatial variability at close proximity. The analyses revealed that the coefficient of variation of cone resistance can be presented as 20% independent of the depth. Geo-statistics has been shown to be a useful technique in the assessment of inherent random heterogeneity of weathered granitic profiles. Semi-variogram analyses showed that the Spherical Models is best fitted to represent the spatial autocorrelation and prediction of cone resistance for areas covered with weathering remnants of granitic rocks.
In monsoon periods, slope failures are major natural disasters in western Japan where most of the... more In monsoon periods, slope failures are major natural disasters in western Japan where most of the areas are covered with weathered Granite (Masado) or weathered Rhyolite. The present hazard assessment system available to predict such catastrophic events in the region is not adequate for early evacuation purposes as it is not based on any reliable geotechnical assessments. To incorporate geotechnical inputs and to enhance present risk assessment, this study was proposed and initially a method to determine shear strength parameters was established. Authors have been already established a sound methodology and relationships to determine shear strength parameters for weathered Granite and the present study focuses to develop the same for weathered Rhyolite and to propose a method to evaluate real time factor of safety based on real time rainfall data. A series of laboratory model tests based on lightweight dynamic cone penetrometer and direct shear tests were conducted on weathered Rhyolite collected at Shobara city, Japan. Good graphical relationships were developed with cone resistance, qd and void ratio e, void ratio e and apparent cohesion cd, and void ratio e and internal friction angle φd. Stability analyses were conducted considering shear strength parameters and the water table estimated based on real time rainfall data. It was found that the time of occurring slope failures are well evaluated from the proposed method logy from this study. This study can be extended to evaluate slope failures in forecasted rainfall conditions.
Geotechnical investigation of natural slopes is challengeable especially when natural slopes havi... more Geotechnical investigation of natural slopes is challengeable especially when natural slopes having higher gradients and access is difficult. Also, it is even more problematic to find the shear strength parameters spatially to evaluate the stability of slopes as most of the methods available to find the shear strength parameters in the literature are uneconomical or such methods cannot be applied in vegetated slopes. Recently, authors have conducted a series of in situ investigations based on the newly developed lightweight dynamic cone penetrometer to examine its applicability in analyzing the slopes covered with weathering remnants of decomposed granite. Six patterns were identified based on the penetration resistance varies with the depth. Spatial variability analysis conducted on different grid spaces showed that the coefficient of variation of cone resistance varies from 0 to 35 %. Semi-variogram analysis showed that the Spherical Models can be used to evaluate the spatial variability of weathering remnants of decomposed granite. A series of laboratory calibration tests based on the lightweight dynamic cone penetration tests and direct shear tests with pore pressure measurements were conducted at different void ratios and degrees of saturation. Based on the laboratory calibration test results, a method to determine the void ratio, e, from the data of q d was presented. Based on this, two formulas to evaluate the shear strength parameters, apparent cohesion and friction angle, were established with the cone resistance and degree of saturation. Slight modification was proposed in evaluating the apparent cohesion with respect to the different fine content in the soils. As a whole, the proposed method can be successfully applied to individual slopes to determine the profile thickness and to evaluate the shear strength parameters spatially. Based on this, hazard assessment of individual slopes can be made.
Natural Hazards, 2014
Your article is published under the Creative Commons Attribution license which allows users to re... more Your article is published under the Creative Commons Attribution license which allows users to read, copy, distribute and make derivative works, as long as the author of the original work is cited. You may selfarchive this article on your own website, an institutional repository or funder's repository and make it publicly available immediately.
Marine Georesources & Geotechnology, 2016
Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No... more Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No. 1 nuclear power plant is an urgent requirement. The purpose of this study was to develop a sealing material which can be used as an engineered barrier for a final disposal facility for the soils and wastes contaminated by radioactive cesium. The analyses conducted based on 4-m-thick sealing layer revealed that the hydraulic conductivity of the sealing material needs to be kept below 5.0 � 10 À 10 m/s to avoid the seepage of contaminants below the environmentally safe limits. Sealing material was developed using marine clay-bentonite mixture and the engineering characteristics were examined. The results of laboratory experiments showed that, with the addition of bentonite, the hydraulic conductivity equal to or less than 5.0 � 10 À 10 m/s was achieved when the effective consolidation stress is equal to or more than 27 kPa. From the tests for adsorption properties for cesium, it was found that the sealing material showed the significant capacity of adsorption for cesium in seawater. It was concluded that the construction of waste disposal facility on the sandy seafloor is feasible using the sealing layer proposed in this study.
SOILS AND FOUNDATIONS, 2011
Lecture Notes in Civil Engineering
Geotechnical Engineering for Disaster Mitigation and Rehabilitation, 2008
Shallow slope failures, induced by torrential rainfall, are common in the western Japan, where Ma... more Shallow slope failures, induced by torrential rainfall, are common in the western Japan, where Masado, a regional soil made of decomposed granite, is widely distributed in natural slopes. There is quite a few information on the geotechnical conditions, because of the difficulty of ground investigation on steep slopes with lush vegetation. The lightweight dynamic cone penetration test (LWDCPT) has been
Doboku Gakkai Ronbunshuu C, 2007
Slope failures caused by rainfall on weathered granite are common occurrences in many parts of th... more Slope failures caused by rainfall on weathered granite are common occurrences in many parts of the world and it is more severe in Japan where there are a significant number of slopes susceptible to failure. At present, about 31,987 natural, and valley slopes are found to be susceptible to landslide disasters in Hiroshima Prefecture, the highest number of any prefecture in Japan. In Hiroshima Prefecture, the prefectural land is divided into 350 units of 5 km 2 , and the hazard of each unit was assessed based on the rainfall data and past records of failures. However, the existing hazard assessment system was found not to be adequate of making better predictions of individual failures in the region, and moreover the system was developed without carrying out any reliable slope stability analyses. In this study, an attempt has been made to understand the mechanism of individual slope failure through seepage analyses and stability analyses. A series of laboratory model tests were conducted to develop the relationships among volumetric water content, degree of saturation, suction, and coefficient of hydraulic conductivity under unsaturated conditions. Field investigation and laboratory tests were conducted based on the four valleys which were identified as potentially hazardous zones in Higashi-Hiroshima city in Hiroshima Prefecture. Graphical relationships were developed among the volumetric water content, suction, rainfall intensity, coefficient of hydraulic conductivity, and degree of saturation for Masado soils. Based on the relationships developed, suction was calculated along the soil profile of natural valleys with the lapse of time. Thus, shear strength parameters were determined based on the degree of saturation calculated from the data of volumetric water contents. The stability analyses revealed that the factor of safety gradually decreases with the formation of High Moisture Content Belt (HMCB) and drastically reduces with the formation of the water table. The susceptibility of failure for each of the four valleys is given based on the hazard assessment system, and is compared and discussed.
A major problem in the geotechnical approach to the stability of natural slopes is that there is ... more A major problem in the geotechnical approach to the stability of natural slopes is that there is usually little information on the in-situ geotechnical conditions, because of the extreme di‹culty associated with ground investigations of steep slopes covered with vegetation. In this study, a lightweight dynamic cone penetration test (LWDCPT) has been introduced for a geotechnical survey of natural weathered granitic (Masado) slopes. Based on a series of direct shear tests, the internal friction angle and the apparent cohesion of reconstituted Masado soil were found to be fairly closely related to the void ratio and the degree of saturation in the soil. From the laboratory calibration tests, an equation was created to relate the dynamic cone resistance (q d ) and the void ratio of reconstituted Masado under diŠerent degrees of saturation. Equations were developed to calculate the internal friction angle and the apparent cohesion from the value of qd for Masado at a known degree of saturation. LWDCPT and direct shear tests were carried out on undisturbed samples taken from a natural Masado slope. The estimated internal friction angle and the apparent cohesion calculated with the value of qd in the LWDCPTs agreed fairly well with those of tests on the undisturbed samples obtained in laboratory shear tests.
Erratum Erratum to "Practical slip circle method of slices for calculation of bearing capacity fa... more Erratum Erratum to "Practical slip circle method of slices for calculation of bearing capacity factors" [Soils Found. 54 (6) (2014) 1127-1144] Soils and Foundations http://dx.
Soils derived from granitic rocks exhibit a complex degree of variability in space. A grid was es... more Soils derived from granitic rocks exhibit a complex degree of variability in space. A grid was established having 5 m intervals spanning 50 m in length and 20 m in width in order to investigate inherent random heterogeneity of areas covered with weathered granite. Six major patterns of cone resistance varies with the depth were identified. Main grid was further divided at selected locations in 1m grids and at one location in 25 cm grids spanning 1 m in both directions for better understanding of spatial variability at close proximity. The analyses revealed that the coefficient of variation of cone resistance can be presented as 20% independent of the depth. Geo-statistics has been shown to be a useful technique in the assessment of inherent random heterogeneity of weathered granitic profiles. Semi-variogram analyses showed that the Spherical Models is best fitted to represent the spatial autocorrelation and prediction of cone resistance for areas covered with weathering remnants of granitic rocks.
In monsoon periods, slope failures are major natural disasters in western Japan where most of the... more In monsoon periods, slope failures are major natural disasters in western Japan where most of the areas are covered with weathered Granite (Masado) or weathered Rhyolite. The present hazard assessment system available to predict such catastrophic events in the region is not adequate for early evacuation purposes as it is not based on any reliable geotechnical assessments. To incorporate geotechnical inputs and to enhance present risk assessment, this study was proposed and initially a method to determine shear strength parameters was established. Authors have been already established a sound methodology and relationships to determine shear strength parameters for weathered Granite and the present study focuses to develop the same for weathered Rhyolite and to propose a method to evaluate real time factor of safety based on real time rainfall data. A series of laboratory model tests based on lightweight dynamic cone penetrometer and direct shear tests were conducted on weathered Rhyolite collected at Shobara city, Japan. Good graphical relationships were developed with cone resistance, qd and void ratio e, void ratio e and apparent cohesion cd, and void ratio e and internal friction angle φd. Stability analyses were conducted considering shear strength parameters and the water table estimated based on real time rainfall data. It was found that the time of occurring slope failures are well evaluated from the proposed method logy from this study. This study can be extended to evaluate slope failures in forecasted rainfall conditions.
Geotechnical investigation of natural slopes is challengeable especially when natural slopes havi... more Geotechnical investigation of natural slopes is challengeable especially when natural slopes having higher gradients and access is difficult. Also, it is even more problematic to find the shear strength parameters spatially to evaluate the stability of slopes as most of the methods available to find the shear strength parameters in the literature are uneconomical or such methods cannot be applied in vegetated slopes. Recently, authors have conducted a series of in situ investigations based on the newly developed lightweight dynamic cone penetrometer to examine its applicability in analyzing the slopes covered with weathering remnants of decomposed granite. Six patterns were identified based on the penetration resistance varies with the depth. Spatial variability analysis conducted on different grid spaces showed that the coefficient of variation of cone resistance varies from 0 to 35 %. Semi-variogram analysis showed that the Spherical Models can be used to evaluate the spatial variability of weathering remnants of decomposed granite. A series of laboratory calibration tests based on the lightweight dynamic cone penetration tests and direct shear tests with pore pressure measurements were conducted at different void ratios and degrees of saturation. Based on the laboratory calibration test results, a method to determine the void ratio, e, from the data of q d was presented. Based on this, two formulas to evaluate the shear strength parameters, apparent cohesion and friction angle, were established with the cone resistance and degree of saturation. Slight modification was proposed in evaluating the apparent cohesion with respect to the different fine content in the soils. As a whole, the proposed method can be successfully applied to individual slopes to determine the profile thickness and to evaluate the shear strength parameters spatially. Based on this, hazard assessment of individual slopes can be made.