Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on th...Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers(HCTs) during direct shear of infilled joints under constant normal stiffness(CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using threedimensional(3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients(JRCs) of 8-10 and 18-20 with the ratios of infill thickness to asperity height(t/a)equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness.展开更多
The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this pap...The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.展开更多
A simplified analytical approach is proposed for predicting the load-displacement behavior of single piles in unsaturated soils considering the contribution from the nonlinear shear strength and soil stiffness influen...A simplified analytical approach is proposed for predicting the load-displacement behavior of single piles in unsaturated soils considering the contribution from the nonlinear shear strength and soil stiffness influenced by matric suction.This approach includes a Modified Load Transfer Model(MLTM)that can predict the nonlinear relationships between the shear stress and pile-soil relative displacement along the pile shaft,and between the pile base resistance and base settlement.The proposed model is also extended for pile groups to incorporate the interaction effects between individual piles.The analytical approach is validated through a comparative analysis with the measurements from two single pile tests and one pile group test.In addition,a finite element analysis using 3D modeling is carried out to investigate the behavior of pile groups in various unsaturated conditions.This is accomplished with a user-defined subroutine that is written and implemented in ABAQUS to simulate the nonlinear mechanical behavior of unsaturated soils.The predictions derived from the proposed analytical and numerical methods compare well with the measurements of a published experimental study.The proposed methodologies have the potential to be applied in geotechnical engineering practice for the rational design of single piles and pile groups in unsaturated soils.展开更多
为获取盐渍土蒸发过程中总吸力、基质吸力及渗透吸力的大小,阐明不同水盐条件下各吸力动态变化特征及其对蒸发的影响,将冷镜露点水势仪(WP4C)和并行接触式滤纸法相结合,对不同含盐量土壤蒸发过程中总吸力、基质吸力与渗透吸力的动态过...为获取盐渍土蒸发过程中总吸力、基质吸力及渗透吸力的大小,阐明不同水盐条件下各吸力动态变化特征及其对蒸发的影响,将冷镜露点水势仪(WP4C)和并行接触式滤纸法相结合,对不同含盐量土壤蒸发过程中总吸力、基质吸力与渗透吸力的动态过程及其对土壤蒸发的影响进行了分析;选取4种常用土壤水分特征曲线模型,利用SWRC-Fit对基质吸力与含水量之间的关系进行了拟合。结果表明:盐渍土在蒸发过程中基质吸力与渗透吸力占总吸力的比例不断发生变化,相同含水率下渗透吸力占比始终大于基质吸力;含水率与盐分均会影响土壤渗透吸力的大小,其中盐分的影响更显著。土壤蒸发.强度及持续时间均会受到土壤盐分影响。通过WP4C与并行接触式滤纸法可以同时获取蒸发过程中非饱和土壤的总吸力、基质吸力与渗透吸力,Fredlund and Xing(FX)模型能够较好地拟合实验蒸发过程中的实测数据,在蒸发各阶段均有较好拟合精度,也进一步证明了实验方法与数据的可靠性。展开更多
基金The financial support provided by the China Scholarship Council (Grant No. 201406420027)
文摘Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers(HCTs) during direct shear of infilled joints under constant normal stiffness(CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using threedimensional(3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients(JRCs) of 8-10 and 18-20 with the ratios of infill thickness to asperity height(t/a)equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness.
基金the National Natural Science Foundation of China (Grant No. 19972068).
文摘The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.
基金financially supported by NSERC,CanadaDiscovery Grant 2020(Grant No.5808).
文摘A simplified analytical approach is proposed for predicting the load-displacement behavior of single piles in unsaturated soils considering the contribution from the nonlinear shear strength and soil stiffness influenced by matric suction.This approach includes a Modified Load Transfer Model(MLTM)that can predict the nonlinear relationships between the shear stress and pile-soil relative displacement along the pile shaft,and between the pile base resistance and base settlement.The proposed model is also extended for pile groups to incorporate the interaction effects between individual piles.The analytical approach is validated through a comparative analysis with the measurements from two single pile tests and one pile group test.In addition,a finite element analysis using 3D modeling is carried out to investigate the behavior of pile groups in various unsaturated conditions.This is accomplished with a user-defined subroutine that is written and implemented in ABAQUS to simulate the nonlinear mechanical behavior of unsaturated soils.The predictions derived from the proposed analytical and numerical methods compare well with the measurements of a published experimental study.The proposed methodologies have the potential to be applied in geotechnical engineering practice for the rational design of single piles and pile groups in unsaturated soils.
文摘为获取盐渍土蒸发过程中总吸力、基质吸力及渗透吸力的大小,阐明不同水盐条件下各吸力动态变化特征及其对蒸发的影响,将冷镜露点水势仪(WP4C)和并行接触式滤纸法相结合,对不同含盐量土壤蒸发过程中总吸力、基质吸力与渗透吸力的动态过程及其对土壤蒸发的影响进行了分析;选取4种常用土壤水分特征曲线模型,利用SWRC-Fit对基质吸力与含水量之间的关系进行了拟合。结果表明:盐渍土在蒸发过程中基质吸力与渗透吸力占总吸力的比例不断发生变化,相同含水率下渗透吸力占比始终大于基质吸力;含水率与盐分均会影响土壤渗透吸力的大小,其中盐分的影响更显著。土壤蒸发.强度及持续时间均会受到土壤盐分影响。通过WP4C与并行接触式滤纸法可以同时获取蒸发过程中非饱和土壤的总吸力、基质吸力与渗透吸力,Fredlund and Xing(FX)模型能够较好地拟合实验蒸发过程中的实测数据,在蒸发各阶段均有较好拟合精度,也进一步证明了实验方法与数据的可靠性。
