干湿循环含低应力条件下百色膨胀土抗剪强度试验研究

Experimental Study on Shear Strength of Baise Expansive Soil under Low Stress and Dry-wet Cycle

浅层坍滑是膨胀土边坡在大气干湿循环作用下必然发生的地质灾害,常给膨胀土地区工程建设带来极大困扰。为探究特定边界条件下膨胀土的真实强度,文章开展了干湿循环含低应力条件下百色膨胀土常规饱和慢剪试验,对比分析了摩尔库伦直线、双直线、广义幂函数法拟合所得抗剪强度参数及低应力段三法拟合值与实测值的差异,得到随循环次数增加,三法拟合所得抗剪强度参数均呈大幅衰减,且衰减主要体现在粘聚力(或纵轴交点值)的大幅降低上,内摩擦角虽有减小,但降幅不大;低应力段抗剪强度实测值与摩尔库伦直线法拟合值差异大,而双直线、广义幂函数法差异小,表明低应力下膨胀土强度包线具有明显非线性特征,验证了已有研究成果的合理性。

Shallow slump is a kind of geological disaster of expansive soil slope which is inevitable under the action of atmospheric dry-wet cycle,which often brings great trouble to the engineering construction in expansive soil area.In order to explore the true strength of expansive soil under specific boundary conditions,this article conducted the conventional saturated slow-shear test of Baise expansive soil under low stress and dry-wet cycle condition, compared and analyzed the anti-shear strength parameters obtained from the fitting of Mohr-Coulomb straight line, double straight line and generalized power function method and the difference between actual measured value and three- methods fitting value at low stress section, then obtained that, with the increase of cycling number, the shear strength parameters obtained from the fitting of three methods are significantly attenuated, and attenuation is mainly reflected in the significant decrease of cohesion（or vertical axis junction value）, although the internal friction angle is reduced, the reduction is not but; the difference between the measured value of shear strength at low stress section and the fitting value of Mohr-Coulomb straight line method is large,while the difference by the double straight line and generalized power function method is small, indicating that the strength of expansive soil under low stress has obvious nonlinear characteristics,which proves the rationality of existing research results.