干湿循环下粉质黏土强度及变形特性试验研究

Experimental study on strength and deformation characteristics of silty clay during wetting-drying cycles

为了研究干湿循环作用下粉质黏土强度及变形特性的变化规律,以取自三峡库区某边坡的原状粉质黏土为研究对象,通过干湿循环和三轴剪切试验,对不同荷载条件下,经历不同干湿循环次数的粉质黏土的强度和变形进行了研究。结果表明:随着干湿循环次数的增加,强度峰值、有效黏聚力和割线模量都逐渐降低,且先快后慢;而有效内摩擦角保持稳定。干湿循环对原状粉质黏土强度和变形特性的劣化是因为裂隙的开展破坏了土体的结构。荷载约束了干湿循环时裂隙开展,从而抑制了干湿循环的劣化作用,荷载越大,抑制能力越强。最后,通过拟合试验数据,对干湿循环作用下的原状粉质黏土的摩尔-库仑强度准则表达式进行了修正。

To study the strength and deformation characteristics of silty clay during wetting-drying cycles, the undisturbed silty clay is taken from a slope located in Three Gorges Reservoir Region, China. A series of triaxial shear tests are conducted under different load conditions after wetting-drying cycles. The test results indicate that the peak strength, effective cohesion and secant modulus all decrease slowly with the increasing number of wetting-drying cycles. While the effective internal friction angle stays at a steady state. The reason for the deterioration of strength and deformation of the silty clay in wetting-drying cycles is the crack development, which undermines the soil structure. However, external loading can positively restrict the crack development caused by wetting-drying cycles. By fitting the test data, the expression of Mohr-Coulomb yielding criterion for the undisturbed silty clay under wetting-drying cycles is modified.