The Experts below are selected from a list of 1917 Experts worldwide ranked by ideXlab platform

Toshihiro Noda - One of the best experts on this subject based on the ideXlab platform.

  • simulation and evaluation of improvement effects by vertical drains vacuum consolidation on peat ground under embankment loading based on a macro element method with water absorption and discharge functions
    Soils and Foundations, 2015
    Co-Authors: Hongson Nguyen, Mutsumi Tashiro, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The authors previously extended the macro-element method proposed by Sekiguchi to include water absorption and discharge functions and incorporated this into a soil–water coupled finite deformation analysis code capable of accounting for inertial forces. The primary objective of this study is to validate the ability of the proposed method to simulate actual ground behavior by comparing the simulation results with the actual measurements of the embankment loading of a soft peat ground improved with vertical drains and vacuum consolidation. It was found that the proposed method is capable of comprehensively and closely simulating not only the magnitude of Settlement, but also various ground behaviors, including the deformation of the surrounding ground and pore water pressure distributions. Furthermore, additional simulations were performed to elucidate the effect of a continuous middle sand layer found to exist and to span the entire improved area at an actual embankment site. The next objective of this study is to investigate the impact of ground improvement, using vertical drains and vacuum consolidation with embankment loading on a soft ground, placing a particular focus on the effect of drain spacing. In this case, an ultra-soft ground with alternating peat and clay layers was modeled to represent a typical ground to which vacuum consolidation would be applied. Based on a series of simulations, it was found that, although the use of vacuum consolidation in combination with vertical drains is effective in cases where it is necessary to limit the deformation of the surrounding ground, the same reduction in Residual Settlement can be achieved using vertical drains alone, provided that the drains are deployed at a sufficient frequency.

  • simulation of large scale deformation of ultra soft peaty ground under test embankment loading and investigation of effective countermeasures against Residual Settlement and failure
    Soils and Foundations, 2015
    Co-Authors: Mutsumi Tashiro, Son Hong Nguyen, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The construction of a test embankment on ultra-soft ground containing an approximately 50-m-deep soft peat layer with N -values of 0 to 1 did not result in catastrophic slip failure during construction but did cause substantial deformation of the adjacent ground. In addition, large-scale Settlement in excess of 11 m occurred in the approximately 3 years following embankment construction. Based on field observations, it became evident that this large Settlement was attributable to delayed compression of the deep peat layer, which was assumed at the design stage not to be subject to Settlement. Based on laboratory tests and site investigations, it was deduced that due to depositions under continuous artesian conditions, this peat layer had an extremely low consolidation yield stress and was in a state such that even a slight increase in stress would result in large-scale compression. After confirming the ability of the analysis code based on soil–water coupled finite deformation theory, which included an elasto-plastic constitutive equation describing the behavior of the soil skeleton, to reproduce the observed ground behavior, the code was used to predict future Settlement. These simulations were then used to evaluate the effectiveness of countermeasures aimed not only at improving stability during construction, but also at reducing Residual Settlement. The results of these analyses were applied in the planning of large-scale repair work performed on the test embankment. Also, when an embankment was subsequently constructed near the test embankment on similar ultra-soft ground, ground improvements were conducted prior to embankment construction as a countermeasure against Residual Settlement. In this paper, valuable field data related to these latter construction efforts is also presented.

  • prediction of Settlement in natural deposited clay ground with risk of large Residual Settlement due to embankment loading
    Soils and Foundations, 2011
    Co-Authors: Mutsumi Tashiro, Motohiro Inagaki, Toshihiro Noda, Masaki Nakano, Akira Asaoka
    Abstract:

    This study endeavors to predict the Settlement that could occur in the future at a site where Settlement due to embankment loading is already occurring at present. In the site studied here, large Residual Settlement of as much as 70 cm has already occurred in the 4 years since it entered into service. It is believed that Settlement will also continue in the future because excess pore pressure is still present within the clay layers. Furthermore, according to the method of evaluation proposed previously by the authors, which is based on the sensitivity and compression index ratios, it can be judged that the ground includes clays that are sensitive to disturbance and have a strong possibility of large Residual Settlement. In this paper, simulation of the Settlement observed up to now at the site as well as prediction of the Settlement that could occur in the future was carried out by deducing the higher compressibilities possessed by the in-situ clays compared with the undisturbed clay specimens in the laboratory. The soil-water coupled finite deformation analysis was employed using the analysis program GEOASIA, in which the constitutive equation for the soil skeleton is mounted with the SYS Cam-clay model. In addition, the effect of modifying the vertical section of the embankment by overlaying in order to counter the Settlement was also investigated by numerical analysis. The results showed that such a countermeasure cannot be expected to lead to faster consolidation and that it may require massive funding over a long period of time to cover the maintenance and management costs involved.

Mutsumi Tashiro - One of the best experts on this subject based on the ideXlab platform.

  • simulation and evaluation of improvement effects by vertical drains vacuum consolidation on peat ground under embankment loading based on a macro element method with water absorption and discharge functions
    Soils and Foundations, 2015
    Co-Authors: Hongson Nguyen, Mutsumi Tashiro, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The authors previously extended the macro-element method proposed by Sekiguchi to include water absorption and discharge functions and incorporated this into a soil–water coupled finite deformation analysis code capable of accounting for inertial forces. The primary objective of this study is to validate the ability of the proposed method to simulate actual ground behavior by comparing the simulation results with the actual measurements of the embankment loading of a soft peat ground improved with vertical drains and vacuum consolidation. It was found that the proposed method is capable of comprehensively and closely simulating not only the magnitude of Settlement, but also various ground behaviors, including the deformation of the surrounding ground and pore water pressure distributions. Furthermore, additional simulations were performed to elucidate the effect of a continuous middle sand layer found to exist and to span the entire improved area at an actual embankment site. The next objective of this study is to investigate the impact of ground improvement, using vertical drains and vacuum consolidation with embankment loading on a soft ground, placing a particular focus on the effect of drain spacing. In this case, an ultra-soft ground with alternating peat and clay layers was modeled to represent a typical ground to which vacuum consolidation would be applied. Based on a series of simulations, it was found that, although the use of vacuum consolidation in combination with vertical drains is effective in cases where it is necessary to limit the deformation of the surrounding ground, the same reduction in Residual Settlement can be achieved using vertical drains alone, provided that the drains are deployed at a sufficient frequency.

  • simulation of large scale deformation of ultra soft peaty ground under test embankment loading and investigation of effective countermeasures against Residual Settlement and failure
    Soils and Foundations, 2015
    Co-Authors: Mutsumi Tashiro, Son Hong Nguyen, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The construction of a test embankment on ultra-soft ground containing an approximately 50-m-deep soft peat layer with N -values of 0 to 1 did not result in catastrophic slip failure during construction but did cause substantial deformation of the adjacent ground. In addition, large-scale Settlement in excess of 11 m occurred in the approximately 3 years following embankment construction. Based on field observations, it became evident that this large Settlement was attributable to delayed compression of the deep peat layer, which was assumed at the design stage not to be subject to Settlement. Based on laboratory tests and site investigations, it was deduced that due to depositions under continuous artesian conditions, this peat layer had an extremely low consolidation yield stress and was in a state such that even a slight increase in stress would result in large-scale compression. After confirming the ability of the analysis code based on soil–water coupled finite deformation theory, which included an elasto-plastic constitutive equation describing the behavior of the soil skeleton, to reproduce the observed ground behavior, the code was used to predict future Settlement. These simulations were then used to evaluate the effectiveness of countermeasures aimed not only at improving stability during construction, but also at reducing Residual Settlement. The results of these analyses were applied in the planning of large-scale repair work performed on the test embankment. Also, when an embankment was subsequently constructed near the test embankment on similar ultra-soft ground, ground improvements were conducted prior to embankment construction as a countermeasure against Residual Settlement. In this paper, valuable field data related to these latter construction efforts is also presented.

  • prediction of Settlement in natural deposited clay ground with risk of large Residual Settlement due to embankment loading
    Soils and Foundations, 2011
    Co-Authors: Mutsumi Tashiro, Motohiro Inagaki, Toshihiro Noda, Masaki Nakano, Akira Asaoka
    Abstract:

    This study endeavors to predict the Settlement that could occur in the future at a site where Settlement due to embankment loading is already occurring at present. In the site studied here, large Residual Settlement of as much as 70 cm has already occurred in the 4 years since it entered into service. It is believed that Settlement will also continue in the future because excess pore pressure is still present within the clay layers. Furthermore, according to the method of evaluation proposed previously by the authors, which is based on the sensitivity and compression index ratios, it can be judged that the ground includes clays that are sensitive to disturbance and have a strong possibility of large Residual Settlement. In this paper, simulation of the Settlement observed up to now at the site as well as prediction of the Settlement that could occur in the future was carried out by deducing the higher compressibilities possessed by the in-situ clays compared with the undisturbed clay specimens in the laboratory. The soil-water coupled finite deformation analysis was employed using the analysis program GEOASIA, in which the constitutive equation for the soil skeleton is mounted with the SYS Cam-clay model. In addition, the effect of modifying the vertical section of the embankment by overlaying in order to counter the Settlement was also investigated by numerical analysis. The results showed that such a countermeasure cannot be expected to lead to faster consolidation and that it may require massive funding over a long period of time to cover the maintenance and management costs involved.

Motohiro Inagaki - One of the best experts on this subject based on the ideXlab platform.

  • simulation and evaluation of improvement effects by vertical drains vacuum consolidation on peat ground under embankment loading based on a macro element method with water absorption and discharge functions
    Soils and Foundations, 2015
    Co-Authors: Hongson Nguyen, Mutsumi Tashiro, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The authors previously extended the macro-element method proposed by Sekiguchi to include water absorption and discharge functions and incorporated this into a soil–water coupled finite deformation analysis code capable of accounting for inertial forces. The primary objective of this study is to validate the ability of the proposed method to simulate actual ground behavior by comparing the simulation results with the actual measurements of the embankment loading of a soft peat ground improved with vertical drains and vacuum consolidation. It was found that the proposed method is capable of comprehensively and closely simulating not only the magnitude of Settlement, but also various ground behaviors, including the deformation of the surrounding ground and pore water pressure distributions. Furthermore, additional simulations were performed to elucidate the effect of a continuous middle sand layer found to exist and to span the entire improved area at an actual embankment site. The next objective of this study is to investigate the impact of ground improvement, using vertical drains and vacuum consolidation with embankment loading on a soft ground, placing a particular focus on the effect of drain spacing. In this case, an ultra-soft ground with alternating peat and clay layers was modeled to represent a typical ground to which vacuum consolidation would be applied. Based on a series of simulations, it was found that, although the use of vacuum consolidation in combination with vertical drains is effective in cases where it is necessary to limit the deformation of the surrounding ground, the same reduction in Residual Settlement can be achieved using vertical drains alone, provided that the drains are deployed at a sufficient frequency.

  • simulation of large scale deformation of ultra soft peaty ground under test embankment loading and investigation of effective countermeasures against Residual Settlement and failure
    Soils and Foundations, 2015
    Co-Authors: Mutsumi Tashiro, Son Hong Nguyen, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The construction of a test embankment on ultra-soft ground containing an approximately 50-m-deep soft peat layer with N -values of 0 to 1 did not result in catastrophic slip failure during construction but did cause substantial deformation of the adjacent ground. In addition, large-scale Settlement in excess of 11 m occurred in the approximately 3 years following embankment construction. Based on field observations, it became evident that this large Settlement was attributable to delayed compression of the deep peat layer, which was assumed at the design stage not to be subject to Settlement. Based on laboratory tests and site investigations, it was deduced that due to depositions under continuous artesian conditions, this peat layer had an extremely low consolidation yield stress and was in a state such that even a slight increase in stress would result in large-scale compression. After confirming the ability of the analysis code based on soil–water coupled finite deformation theory, which included an elasto-plastic constitutive equation describing the behavior of the soil skeleton, to reproduce the observed ground behavior, the code was used to predict future Settlement. These simulations were then used to evaluate the effectiveness of countermeasures aimed not only at improving stability during construction, but also at reducing Residual Settlement. The results of these analyses were applied in the planning of large-scale repair work performed on the test embankment. Also, when an embankment was subsequently constructed near the test embankment on similar ultra-soft ground, ground improvements were conducted prior to embankment construction as a countermeasure against Residual Settlement. In this paper, valuable field data related to these latter construction efforts is also presented.

  • prediction of Settlement in natural deposited clay ground with risk of large Residual Settlement due to embankment loading
    Soils and Foundations, 2011
    Co-Authors: Mutsumi Tashiro, Motohiro Inagaki, Toshihiro Noda, Masaki Nakano, Akira Asaoka
    Abstract:

    This study endeavors to predict the Settlement that could occur in the future at a site where Settlement due to embankment loading is already occurring at present. In the site studied here, large Residual Settlement of as much as 70 cm has already occurred in the 4 years since it entered into service. It is believed that Settlement will also continue in the future because excess pore pressure is still present within the clay layers. Furthermore, according to the method of evaluation proposed previously by the authors, which is based on the sensitivity and compression index ratios, it can be judged that the ground includes clays that are sensitive to disturbance and have a strong possibility of large Residual Settlement. In this paper, simulation of the Settlement observed up to now at the site as well as prediction of the Settlement that could occur in the future was carried out by deducing the higher compressibilities possessed by the in-situ clays compared with the undisturbed clay specimens in the laboratory. The soil-water coupled finite deformation analysis was employed using the analysis program GEOASIA, in which the constitutive equation for the soil skeleton is mounted with the SYS Cam-clay model. In addition, the effect of modifying the vertical section of the embankment by overlaying in order to counter the Settlement was also investigated by numerical analysis. The results showed that such a countermeasure cannot be expected to lead to faster consolidation and that it may require massive funding over a long period of time to cover the maintenance and management costs involved.

Shotaro Yamada - One of the best experts on this subject based on the ideXlab platform.

  • simulation and evaluation of improvement effects by vertical drains vacuum consolidation on peat ground under embankment loading based on a macro element method with water absorption and discharge functions
    Soils and Foundations, 2015
    Co-Authors: Hongson Nguyen, Mutsumi Tashiro, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The authors previously extended the macro-element method proposed by Sekiguchi to include water absorption and discharge functions and incorporated this into a soil–water coupled finite deformation analysis code capable of accounting for inertial forces. The primary objective of this study is to validate the ability of the proposed method to simulate actual ground behavior by comparing the simulation results with the actual measurements of the embankment loading of a soft peat ground improved with vertical drains and vacuum consolidation. It was found that the proposed method is capable of comprehensively and closely simulating not only the magnitude of Settlement, but also various ground behaviors, including the deformation of the surrounding ground and pore water pressure distributions. Furthermore, additional simulations were performed to elucidate the effect of a continuous middle sand layer found to exist and to span the entire improved area at an actual embankment site. The next objective of this study is to investigate the impact of ground improvement, using vertical drains and vacuum consolidation with embankment loading on a soft ground, placing a particular focus on the effect of drain spacing. In this case, an ultra-soft ground with alternating peat and clay layers was modeled to represent a typical ground to which vacuum consolidation would be applied. Based on a series of simulations, it was found that, although the use of vacuum consolidation in combination with vertical drains is effective in cases where it is necessary to limit the deformation of the surrounding ground, the same reduction in Residual Settlement can be achieved using vertical drains alone, provided that the drains are deployed at a sufficient frequency.

  • simulation of large scale deformation of ultra soft peaty ground under test embankment loading and investigation of effective countermeasures against Residual Settlement and failure
    Soils and Foundations, 2015
    Co-Authors: Mutsumi Tashiro, Son Hong Nguyen, Motohiro Inagaki, Shotaro Yamada, Toshihiro Noda
    Abstract:

    Abstract The construction of a test embankment on ultra-soft ground containing an approximately 50-m-deep soft peat layer with N -values of 0 to 1 did not result in catastrophic slip failure during construction but did cause substantial deformation of the adjacent ground. In addition, large-scale Settlement in excess of 11 m occurred in the approximately 3 years following embankment construction. Based on field observations, it became evident that this large Settlement was attributable to delayed compression of the deep peat layer, which was assumed at the design stage not to be subject to Settlement. Based on laboratory tests and site investigations, it was deduced that due to depositions under continuous artesian conditions, this peat layer had an extremely low consolidation yield stress and was in a state such that even a slight increase in stress would result in large-scale compression. After confirming the ability of the analysis code based on soil–water coupled finite deformation theory, which included an elasto-plastic constitutive equation describing the behavior of the soil skeleton, to reproduce the observed ground behavior, the code was used to predict future Settlement. These simulations were then used to evaluate the effectiveness of countermeasures aimed not only at improving stability during construction, but also at reducing Residual Settlement. The results of these analyses were applied in the planning of large-scale repair work performed on the test embankment. Also, when an embankment was subsequently constructed near the test embankment on similar ultra-soft ground, ground improvements were conducted prior to embankment construction as a countermeasure against Residual Settlement. In this paper, valuable field data related to these latter construction efforts is also presented.

Akira Asaoka - One of the best experts on this subject based on the ideXlab platform.

  • prediction of Settlement in natural deposited clay ground with risk of large Residual Settlement due to embankment loading
    Soils and Foundations, 2011
    Co-Authors: Mutsumi Tashiro, Motohiro Inagaki, Toshihiro Noda, Masaki Nakano, Akira Asaoka
    Abstract:

    This study endeavors to predict the Settlement that could occur in the future at a site where Settlement due to embankment loading is already occurring at present. In the site studied here, large Residual Settlement of as much as 70 cm has already occurred in the 4 years since it entered into service. It is believed that Settlement will also continue in the future because excess pore pressure is still present within the clay layers. Furthermore, according to the method of evaluation proposed previously by the authors, which is based on the sensitivity and compression index ratios, it can be judged that the ground includes clays that are sensitive to disturbance and have a strong possibility of large Residual Settlement. In this paper, simulation of the Settlement observed up to now at the site as well as prediction of the Settlement that could occur in the future was carried out by deducing the higher compressibilities possessed by the in-situ clays compared with the undisturbed clay specimens in the laboratory. The soil-water coupled finite deformation analysis was employed using the analysis program GEOASIA, in which the constitutive equation for the soil skeleton is mounted with the SYS Cam-clay model. In addition, the effect of modifying the vertical section of the embankment by overlaying in order to counter the Settlement was also investigated by numerical analysis. The results showed that such a countermeasure cannot be expected to lead to faster consolidation and that it may require massive funding over a long period of time to cover the maintenance and management costs involved.

  • Mass permeability concept in the analysis of treated ground with sand drains
    Soils and Foundations, 1995
    Co-Authors: Akira Asaoka, Masaki Nakano, G.s.k. Fernando, Mitsuo Nozu
    Abstract:

    When a soft clay foundation under embankment loading is considered, Settlement behavior is affected by the mass permeability and by the magnitude of applied load intensity, which is normalized by the initial undrained bearing capacity. Using these two parameters, the characteristic consolidation Settlement behavior of a clay foundation can be represented by a family of S shaped curves. The range of mass permeability affecting Residual Settlements is confined to a narrow limit. For an embankment foundation, when these two parameters are known, Settlement behavior can be determined uniquely. The effects of improvement of mass permeability by sand drains on a clay foundation are investigated using the macro element method (Sekiguchi et al., 1986). The sand drains improve the mass permeability to 30-300 times that of the non-treated ground. The above findings are applied to two case studies. In the first, where the ground is treated with sand drains under a high applied load it is found that only Settlement observations can be used to assess the usefulness of sand drains in this ground. The other case is on coral soils which exhibit high permeability and a high initial undrained bearing capacity compared with common clay deposits. The effectiveness of sand drains in this ground is evidenced by a significant decrease in Residual Settlement.