干湿循环作用下滑带土的变形演化和强度

干湿循环是一种常见的水—土相互作用方式，对岩土体的变形和强度以及库岸滑坡的稳定性有着重要影响。本文在分析粉土和粉质黏土两种滑带土基本特征的基础上，通过室内干湿循环试验和直接剪切试验，对不同类型的滑带土在干湿循环作用下的变形演化和强度弱化特征进行了试验研究。结果表明：在干湿循环变化下，粉土滑带土的变形表现为风干时土样内部产生裂隙，且随着干湿循环次数的增加，裂隙不断扩展贯穿和增宽，饱和后裂隙又闭合；粉质黏土滑带土变形则为风干时体积收缩，饱和后体积膨胀；两种滑带土在干湿循环条件下的强度弱化规律基本相同，第一次干湿循环造成滑带土强度弱化程度最大，第二次后强度基本趋于稳定值；两种滑带土的黏聚力与干湿循环次数呈对数曲线形式降低，内摩擦角呈线性降低；干湿循环过程中滑带土抗剪强度的降低主要是由于其黏聚力的降低引起的，同时黏聚力受干湿循环的影响较为显著。

Research on the deformation evolution and the strength weaking of slip soil under wetting-drying cycle

Wetting-drying cycling is a common water-soil interaction mode; it plays an important role in the strength and deformation of rock and soil and the stability of landslide. Based on the analysis of the basic characteristics of the slip soil of silt and silty clay, this paper studies on the deformation evolution and strength weakening characteristic of different types of slip soil under the effect of wetting-drying cycle through the indoor dry- wet cycling test and direct shear test. The research results show that in the state of air dried, the deformation behavior of silty soil of slip soil crack in the internal of soil, and with the increase of cycle number, the cracks continue expansion and widening, then the cracks close after saturation; on the other hand, the volume of silty clay is shrinking in air dried condition and expanding after saturation. The strength weakening of the two kinds of slip soil present the same rules under the effect of wetting-drying cycling, the degree of strength weakening is largest at the first cycle of dry and wet, and the strength reaches a certain value after the third cycle. As for shear strength parameters of the two types of slip soil, the reduction of the cohesion in a logarithmic curve form with cycle number, and the angle of internal friction in a linear form with cycle number. Finally, this paper analyzes the sensitivity and significant of the shear strength parameters, we can found that the shear strength of slip soil decrease is mainly due to the lower of cohesive force under the effect of wetting-drying, compared with the internal friction angle, cohesion is affected by the dry-wet circulation is more significant.