干湿循环条件下干燥应力历史对粉质黏土饱和力学特性的影响

以大连地区典型粉质黏土为研究对象,对经历不同干燥应力历史的粉质黏土试样在饱和条件下进行了固结不排水三轴剪切试验。通过对各组试样固结不排水剪切试验的应力-应变关系、孔隙水压力和有效应力路径等试验结果的对比分析,探讨了干燥应力历史对粉质黏土饱和力学特性的影响。固结不排水三轴剪切试验结果表明:干湿循环过程中粉质黏土在饱和条件下的力学特性变化与历史干燥应力有关,历史干燥应力越大,土体在饱和条件下的力学特性变化越明显。相同围压条件下,干湿循环试样的初始剪切刚度比未经历干湿循环的原始试样要高,历史干燥应力越大,初始剪切刚度增长越明显。随着历史干燥应力的增加,干湿循环试样的应力-应变曲线逐渐由应变硬化转变为应变软化,孔隙水压力的发展由先增加后减小转变为孔压持续增长,有效应力路径逐渐由"S"型转变为向左下方发展。干湿循环过程引起了土体的不可逆体积压缩和微裂隙的发展,进而影响土体的饱和力学特性。

Influence of drying stress history on the mechanical behaviors of silty clay under saturated condition

A series of consolidated undrained triaxial tests were performed to measure variations of mechanical behaviors of silt clay from Dalian, China during drying/wetting process. These tests were conducted under the saturated condition after the specimens were subjected to different drying stress histories. By contrastively analyzing the stress-strain relationship,pore-water pressure,and effective stress path of different cases, the influence of drying stress history on the mechanical behaviors of silty clay under saturated condition was studied. The test results show that the influence of drying/wetting on mechanical behaviours of silty clay under saturated condition relates to the drying stress, and the mechanical behaviours are varied more significant with higher drying stress. At the same confining pressure, the shear stiffness of the specimens subjected to drying/wetting cycle are higher than that of the initial specimens during the initial stage of shearing. The higher drying stress that specimens experienced,the higher initial shear stiffness produced. With the increase of the drying stress, the stress-strain relationship curves of silty clay alter from strain hardening to strain softening, and the development of pore water pressure converts from increase following by decrease to continue growing. The effective stress path of the initial specimens is similar to a shape of "S",whereas,the effective stress path of the specimens experienced high drying stress turns to develop towards the lower left side. Irreversible compression of soil skeleton and the micro-cracks develop during drying/wetting process,impacting the mechanical behaviors of silty clay under saturated condition.