Investigation of Soil-water Coupled Behavior of Saturated Clay near/at Critical State and Its Application to Deformation and Failure Problems

为了研究正常固结/超固结粘土的“时间相关性”，进行了三轴压缩试验和亚加载面Cam粘土模型的土-水耦合分析。分叉分析可以用孔隙水迁移效应代替粘塑性效应来解释粘土的“时间相关性”。试验结果表明：1）土样的不排水蠕变破坏是由于孔隙水迁移引起的土样1 ~#<st>破坏模式向2 ~<nd>#破坏模式的转变。2)在排水条件下，超固结粘土在恒定荷载作用下，由于试验过程中的吸水作用，表现为渐进破坏。超固结粘土试件的破坏时间约为6小时。随着轴向应变率的变化，土体逐渐发生破坏。不排水B饱和土柱缺陷敏感分岔 关于我们 采用土-水耦合有限变形分析方法研究了该问题。土样初始几何缺陷为二阶振型余弦曲线。在受载边界上施加了“无角度变化和无方向变化”的线性约束条件。假定土遵循次加载面剑桥模型。当荷载作用在分叉点附近时，荷载-位移曲线开始偏离主路径，最终接近不稳定的第一模态路径，这种模态转换是由于荷载-位移曲线峰值后孔隙水迁移引起的，产生较低的不排水抗剪强度，描述了传统上认为属于粘塑性的不排水蠕变。与试验结果相似，当荷载保持不变时，超固结土样轴向应变速率随轴向应变的增加而增加，说明了由于剪切带软化而导致的渐进破坏的开始。少

In order to investigate "time dependent behavior" of normally consolidated/overconsolidated clay, triaxial compression tests and the soil-water coupled analysis employing the sub-loading surface Cam clay model have been carried out. The bifurcation analysis can explain "time dependent behavior" of clays by using pore water migration effect instead of visco-plasticity. The triaxial compression tests carried out in this research showed that : 1) Undrained creep failure occurs due to the change of 1^<st> failure mode to 2^<nd> mode of soil specimen that associated with pore water migration. 2) Overconsolidated clay exhibits progressive failure under constant loading in drained condition due to the absorbed water during testing. It took about 6 hours for the failure of overconsolidated clay specimen. The progressive failure is observed with the fluctuations of axial strain rates against axial strain.Imperfection-sensitive bifurcation of a plane strain saturated soil column with undrained b … More oundaries is investigated by soil-water coupled finite deformation analysis. An initial cosine-curve geometrical imperfection of 2nd mode is applied to the soil specimen. The linear constraint conditions, "no angle change and no direction change" are imposed over the loaded boundary. The soil is assumed to follow the sub-loading surface Cam-clay model. When the load application to the specimen is held at a point near the bifurcation point, load displacement curve starts to deviate from the main path, ultimately approaching unstable 1st mode path. This mode switching due to pore-water migration after the peak in load-displacement curve, that yield low undrained shear strength describes the undrained creep, which is traditionally attributed to visco-plasticity. Similar to the experiment, the increase in axial strain rate against axial strain in heavily overconsolidated soil specimen when the applied load is kept constant, illustrates the initiation of progressive failure due to softening in the highly sheared zones. Less