干湿循环下花岗岩残积土抗剪强度及边坡稳定性分析

Analysis of the shear strength of granite residual soil and slope stability under wetting-drying cycles

为研究干湿循环对花岗岩残积土抗剪强度特性和抗剪强度参数的影响,分析花岗岩残积土边坡的稳定性,改进了常规的单元试验方法.以整个花岗岩残积土边坡为试验对象进行干湿循环模拟,在每次循环后直接在边坡坡面上切取花岗岩残积土试样进行直剪试验.在此基础上,利用有限元软件ABAQUS对一实际边坡进行了干湿循环的数值模拟,在每次循环模拟前对上一次模拟结果进行分析,将等效塑性应变较大区域的土体强度进行适当折减,分析每次循环后花岗岩残积土边坡的应力应变、稳定性以及塑性变形.试验结果表明:花岗岩残积土的抗剪强度随干湿循环次数、循环幅度的增加而减小,其中黏聚力值衰减明显,内摩擦角的变化相对较小,在3~5次干湿循环后抗剪强度趋于稳定;通过数据分析得到干湿循环的黏聚力公式,进一步得到了干湿循环条件下花岗岩残积土的抗剪强度公式;干湿循环作用导致边坡稳定性降低,安全系数减小,且第一次干湿循环后安全系数的降幅最大.

In order to study the shear strength parameters and characteristics of granite residual soil and stability of slope under wetting-drying cycles,wetting-drying cycles were simulated on the whole granite residual soil slope,instead of the conventional unit test method.After each cycle,direct shear tests on the soil samples fetched from the slope surface were performed.On this basis,wetting-drying cycles were simulated on an actual slope by the finite element software ABAQUS to analyze the stress,strain,stability and plastic deformation of granite residual soil slope under wetting-drying cycles.The last simulation results were analyzed before each cycle simulation and the strength of soils which had large plastic strain was reduced properly.The results showed that the shear strength of granite residual soil decreases with the increase of the number and amplitude of wetting-drying cycles,in which the cohesion decreases obviously and the friction angle changes relatively little.The shear strength is about to stable after third to fifth times of cycles.The cohesion formula and shear strength formula of granite residual soil under wetting-drying cycles are obtained based on the data analysis.Wetting-drying cycles lead to the decrease of slope stability and safety factor,and the decline is the largest after the first cycle.