基于孔压-应力耦合下考虑渗透系数各向异性对库水位骤降边坡的影响

Slopes with different permeability anisotropy characteristics affected by reservoir water level fluctuations based on pore pressure-stress coupling

库水位下降边坡稳定问题是三峡库区滑坡面临的主要问题之一。以往研究多将边坡土体视为渗流各向同性材料,或仅考虑其渗流各向异性程度(kr=kx/ky),而未考虑各向异性方向(α)的影响,且以往的数值模拟研究较少考虑孔压-应力耦合问题,因此,本文基于滑坡地下水渗透力分布与应力-应变分析相结合的数值分析方法,考虑到砂土与黏土土质及各向异性程度kr及α的影响,利用Geostudio中SIGMA/W与SLOPE/W模块对三峡库区蔡坡堆积体库水位下降的渗流、变形及稳定性进行了数值模拟,结果表明:各向异性程度kr及方向α使土体的排渗性能降低,浸润线滞后高程、最大水平位移增大而最小安全系数降低;库水位下降对砂土边坡渗流、变形及稳定性的影响要小于黏土边坡;对于砂土这种渗透系数较大的土体而言,必须考虑各向异性程度kr及各向异性方向α的影响,但是对于渗透系数较小的黏土而言,为简化计算可以仅考虑各向异性程度kr。

Evaluation of slope stability under water level fluctuations is an important topic in the Three Gorges Reservoir(TGR)in China.However,most of the previous studies regarded slope soil as isotropic material,or only considered the influence of anisotropy ratio(kr=k_(x)/k_(y))but ignored the anisotropy direction(α).Meanwhile,the pore pressure-stress coupling was rarely considered in the previ-ous numerical simulations.In the present study,the SIGMA/W and SLOPE/W modules in Geo-studio are utilized to carry out the nu-merical simulation of Caipo slope under the drawdown of the reservoir water level,and the anisotropy ratio(k_(r))as well as the anisotropy direction(α)of two kinds of soils(clay and sand)are included.Results show that the anisotropy ratio kr and anisotropy directionαdecrease the infiltration capacity of the soil,which increases the infiltration line hysteretic elevation as well as maximum horizontal dis-placement,and reduces the minimum safety factor.The influence of reservoir water level drop on seepage,deformation,and stability of the sand slope is less than that of the clay slope.For the sandy soil slope,it is not only necessary to consider the influence of kr,but also the influence ofα.For the soil slope,we can only considerαin order to simplify calculation.