干湿循环条件下不同初始干密度土体的力学特性

利用应力-应变控制式三轴剪切渗透试验仪,测试了大连地区典型粉质黏土试样干湿循环前后的力学特性。通过对干湿循环前后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，探讨了干湿循环对不同初始干密度土体力学特性的影响，结果表明：土体对干湿循环的响应与土体的初始干密度有关。干湿循环使得初始干密度为1.61g/cm3的试样的应力-应变关系曲线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，循环前后有效应力路径的发展趋势发生了明显变化。初始干密度1.71g/cm3和1.76g/cm3试样干湿循环前后的应力-应变关系曲线形式未发生明显改变，干湿循环致使孔隙水压力的峰值所有增加，剪切初始阶段的有效应力路径位于未循环试样的左侧。干湿循环前后土体的电镜扫描（SEM）试验发现，干湿循环导致土骨架的结构性转变。干湿循环过程中试样内部结构调整和基质吸力的压密作用使得土体的力学特性发生了不可逆转的变化。

Mechanical behaviors of soils with different initial dry densities under drying-wetting cycle

A series of consolidation undrained tests were performed using the stress-strain controlled triaxial apparatus to measure variations of mechanical behaviors of silt clay in Dalian during drying-wetting cycle. The stress-strain-relation, effective stress path, pore water pressure of the remolded specimens and the ones subjected to drying-wetting cycles were contrastively analyzed to discuss the effect of drying-wetting cycle on the mechanical behaviors of specimens under different initial dry densities. The test results indicate that the influence of drying-wetting cycle on soils related to the initial dry density of soils. For the specimens with initial dry density of 1.61g/cm3, drying-wetting cycle altered the stress-strain relationship curves from strain hardening to strain softening, the development of pore water pressure converted from increase following by decrease to continue growing, and the effective stress path changed significantly. However, the stress-strain curve form was not changed for the specimens with initial dry density of 1.71g/cm3 and 1.76g/cm3, while the peak value of pore water pressure was increased resulting from drying-wetting, the effective stress path in the initial stage of shear was on the left side of the ones without subjected to drying-wetting cycle. The scanning electron micrographs proved that the drying-wetting cycle resulted in irreversible variation of soils skeleton structure. Rearrangement of the soil microstructure and compaction of the soil skeleton during drying-wetting cycle led to the irreversible change of mechanical behaviors of the soil.