中文摘要：

为获取浅层坍滑膨胀土边坡滑面的真实抗剪强度，设置不同干密度和低应力条件，用常规直剪仪对南宁膨胀土开展饱和快剪、固结快剪、慢剪和残余剪试验，并对干密度1．7g·cm^-3的土样进行干湿循环饱和慢剪试验，系统研究了干密度、试验条件及方法对抗剪强度的影响。结果表明：干密度和应力条件对饱和快剪、固结快剪、慢剪的强度影响显著；低应力下饱和慢剪强度最小；3种抗剪强度线均呈非线性变化，宜用乘幂函数拟合；残余剪与干湿循环慢剪强度值较为接近；与规范法直线回归的残余强度值相比，低应力下的实测值仍小很多。根据该结果提出分析膨胀土坡浅层破坏时，选取土体抗剪强度参数的建议。

英文摘要：

In order to obtain the shear strength of expansive soil for shallow failure slope, the saturated quick shear, consolidated quick shear, slow shear and residual shear tests on Nanning expansive soil were carried out with low stresses and various initial dry densities with the application of conventional direct shear apparatus. In addition, the dry-wet cycle saturated slow shear test was conducted on the soil with initial dry density of 1.7 g · cm a. The influences of low stresses and various initial dry densities on these shear strengths were systematically studied. The results indicate that the saturated quick shear strength, consolidated quick shear strength and slow shear strength are remarkably influenced by low stresses and initial dry densities. Under low stresses, the saturated slow shear strength is the smallest. Three strengths are in nonlinear change and the nonlinear properties can be fitted with the strengths are close to those of the dry-wet cycle low stresses are still far less than those linearly selecting shear strength to analyze expansive so slow shear, power function. The residual shear both measured values of which under fitted values. Therefore, the recommendation for il is provided.