不同含水量及渗透特性下强风化砂岩土边坡稳定性分析

Stability analysis of strongly weathered sandstone soil slopes with different water contents and permeability characteristics

为了探究风化砂岩土含水量的变化及其降雨强度对滑坡稳定性的影响,以万州区恒合乡黄草坪滑坡强风化砂岩土为例,运用非饱和土力学理论,得出土体抗剪强度指标与含水量之间的关系,对强风化砂岩土进行了快剪试验、压缩试验、渗透试验,并运用数值模拟方法对不同含水量以及不同降雨历时下风化砂岩土边坡的最大位移、基质吸力、饱和度及边坡稳定性系数的变化规律进行了分析。结果表明:以最优含水量为临界点,当含水量从11.31%增加至21.57%时,黏聚力从7.28 kPa增加至最大值10.23 kPa后减小到5.10 kPa,内摩擦角从15.28°缓慢减小至7.94°,变形模量由8.97 MPa减小至2.06 MPa,渗透系数与含水量之间呈线性关系其拟合公式为y=5×10^(-6)x+7×10^(-6),在不同含水量作用下,边坡稳定性系数先增大后减小,潜在滑动面的位置由深到浅逐渐增大;在不同降雨历时作用下,基质吸力和饱和度变化速率的大小均依次为坡顶>坡面>坡体内部,边坡的稳定系数由1.71降低至1.01。研究成果可以为强风化砂岩类似边坡在降雨及不同含水量作用下的边坡稳定性研究和治理工程设计的相关研究提供指导。

In order to explore the changes in water content of weathered sandstone soil and the impact of rainfall intensity on landslide stability,taking the strongly weathered sandstone soil of Huangcaoping landslide in Henghe Township,Wanzhou District as an example,the relationship between soil shear strength index and water content was obtained using unsaturated soil mechanics theory.Fast shear tests,compression tests,and permeability tests were conducted on the strongly weathered sandstone soil,and numerical simulation methods were used to analyze the maximum displacement,matrix suction,saturation,and slope stability coefficient of the weathered sandstone soil slope with different water contents and rainfall durations.The results show that with the optimal moisture content as the critical point,when the moisture content increases from 11.31%to 21.57%,the cohesion increases from 7.28 kPa to the maximum value of 10.23 kPa and then decreases to 5.10 kPa;the internal friction angle slowly decreases from 15.28°to 7.94°,and the deformation modulus decreases from the initial 8.97 MPa to 2.06 MPa;there is a linear relationship between the permeability coefficient and moisture content,and the fitting formula is y=5×10^(-6)x+7×10^(-6);with different moisture contents,the slope stability coefficient first increases and then decreases,and the position of the potential sliding surface gradually increases from deep to shallow;with different rainfall durations,the magnitude of substrate suction is in the order of slope top>slope surface>slope interior,and the rate of saturation change is in the order of slope top>slope surface>slope interior;the stability coefficient of the slope decreases from 1.71 to 1.01.The research results can provide guidance for the stability research and treatment engineering design of slopes similar to strongly weathered sandstone with rainfall and different water contents.