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岩土体抗剪强度是分析评价斜坡稳定性的关键指标。为了弄清可溶盐在黄土抗剪特性中的作用程度及控制机制,以兰州重塑黄土为对象,基于直剪试验,研究了黄土抗剪强度及其参数在不同溶滤次数下的变化特征。结果显示,可溶盐对非饱和黄土抗剪强度及黏聚力具有明显非线性弱化作用,而对内摩擦角的影响则相对微弱。其中,抗剪强度与黏聚力随可溶盐的变化规律存在临界分段现象,其降低幅度在溶滤1次时达到最大值,在溶滤5次后近似于0;而降低速率以易溶盐含量2 620 mg/100 g干土为分界值,呈先快后慢的变化特征。上述关系的内在机制是,在溶滤初始阶段,黄土抗剪特性弱化主要源于易溶盐与部分难溶盐分解;随溶滤次数增加,则更多依赖于易溶盐分解与基质吸力减弱。
Shear strength of rock and soil is a key index for analyzing and evaluating slope stability. In order to clarify the role and control mechanism of soluble salt in the shear-resistant behavior of loess, taking Lanzhou remolded loess as an example, the change characteristics of shear strength of loess and its parameters under different leaching times were studied based on the direct shear test . The results show that soluble salt has a significant nonlinear weakening effect on the shear strength and cohesion of unsaturated loess, while the influence on the internal friction angle is relatively weak. Among them, the shear strength and cohesion with the variation of soluble salt critical segmental phenomenon exists, the reduction rate reached the maximum value in the first filtration, after leaching five times to approximate 0; and reduce the rate of easy The dissolved salt content of 2 620 mg / 100 g dry soil was the cutoff value, showing the characteristics of fast and slow changes. The intrinsic mechanism of the above relationship is that in the initial stage of leaching, the weakening of shear-resistant properties of loess is mainly due to the decomposition of soluble salts and some insoluble salts. With the increase of filtration cycles, the dependence of soluble salt decomposition and matrix suction is more dependent .