不同水力路径下非饱和粉质土的破坏与变形特性

摘要

Capillary hysteresis is an intrinsic phenomenon of the unsaturated soil.At the same matric suction,the degree of saturation of a soil with hydraulic histories is different,and the shear strength of the soil is also different.By conducting direct shear tests on the silty soil samples with different hydraulic histories,the result shows that,if the experimental data are represented by net stress,the effective cohesion decreases with degree of saturation and increases with matric suction,whereas the internal friction angle remains constant.If the experimental data are expressed using the effective stress,the shear strength curve can be normalized into a single line,independent of saturation and hydraulic history.Based on the modified Cam clay model,a hardening function of yield stress is developed,which treats the matric suction and saturated degree as internal variables.The proposed model is useful in analyzing the effect of antecedent rainfall on the stability of unsaturated soil slopes.%通过压力板仪、temple仪和直剪仪对非饱和粉土经过脱湿之后和不同含水量状态分别进行抗剪强度试验研究.试验结果表明:如果采用净应力来描述,非饱和土的有效粘聚力随着含水量的增大而减小,或随着基质吸力的增大而增大,但有效内摩擦角基本保持不变.当饱和度相同时,经过脱湿之后的土体有效粘聚力较大,反映出滞回效应.如果采用有效应力来描述,抗剪强度曲线则归一化为一条临界状态线,而与含水量大小和水力路径无关,从而证明了采用有效应力的合理性与有效性.在修正剑桥模型基础上,将饱和度和基质吸力作为内变量,提出屈服强度的硬化函数,建立渗流与变形耦合模型,从而可以考虑前期降雨历史对非饱和土边坡稳定性的影响.