基于三场耦合的膨胀土边坡浅层坍滑数值分析

Numerical Analysis for Shallow Landslides of Expansive Soil Slopes Based on Three Fields Coupling

为研究膨胀土边坡浅层坍滑的原因,利用有限差分软件FLAC^(2D),借鉴已有多场耦合数值计算思路,通过二相流与热模块模拟了降雨条件下坡体内的非饱和渗流过程及膨胀土的吸湿膨胀;并依据膨胀土饱和度与温度及热膨胀系数的转换关系,利用FISH软件编制了程序调用两模块的信息,实时模拟了土的吸湿膨胀效应,实现了考虑地下水位和渗透系数变化、强度衰减三因素下的膨胀土坡渗流场-位移场-应力场的三场耦合。并基于此,建立了考虑和未考虑膨胀变形的数值模型,分别模拟了降雨条件下计及和未计吸湿膨胀的边坡非饱和渗流过程及其稳定性,对比分析同降雨强度但不同历时、是否计及吸湿膨胀边坡的渗流场及稳定性的差异,揭示膨胀土吸湿膨胀是引起边坡浅层坍滑的重要原因;据此进一步研究不同降雨强度、降雨历时下膨胀土边坡的稳定性,同时对比分析边坡渗流场和应力场的变化及其分布规律,得到不同降雨条件对边坡浅层坍滑的影响。

To revealing the reasons for shallow landslides of expansive soil slopes,in reference to the existing calculation ways of multifield-coupling numerical analysis,the seepage processes from unsaturation to saturation in expansive soil slopes and hygroscopic expansion processes were simulated by the two-phase flow module and thermal module of the finite difference software FLAC^(2D);based on the transformation relations for saturation degrees,temperatures and thermal expansion coefficients of expansive soil and integrating and extracting the information from both of the modules simultaneously,the hygroscopic expansion effect of expansive soil was simulated in time;the three fields involving the seepage field,displacement field and stress field were coupled under consideration for the changes of groundwater levels and permeability coefficients and intensity attenuation.And then,the numerical model with or without expansive deformation was constructed.The seepage processes from unsaturation to saturation in slopes considered and not considered the hygroscopic expansion during rainfall and the stability of slopes were simulated individually;the difference of seepage fields and slopes stability between considering and not considering the hygroscopic expansion effect in the same rainfall intensities but different rainfall duration was contrasted and analyzed.The important reason caused shallow landslides of expansive soil slopes was revealed,it was hygroscopic expansion of expansive soil.Furthermore,the stability of expansive soil slopes under different rainfall intensities and durations was further studied,the variation and distribution of the seepage field and stress field in slopes were compared and analyzed at the same time,and the effects of different rainfall conditions on shallow landslides were obtained.