降雨条件下斜坡软弱地基路堤瞬态稳定性分析

Transient Stability of Embankment over Sloped Weak Ground Subjected to Rainfall Condition

依据Fredlund非饱和土双应力变量强度理论,结合瞬态饱和—非饱和渗流的有限元法和极限平衡法,运用GeoStudio软件中的SEEP/W模块和SLOPE/W模块,进行降雨条件下斜坡软弱地基路堤瞬态稳定性的分析。结果表明:斜坡软弱地基路堤的稳定安全系数随着路堤土和软弱土吸附强度的减小呈近似线性降低趋势;降雨强度越大,雨中和雨后的路堤稳定安全系数降低的速率越快;路堤的稳定安全系数随降雨持时的增长不断下降,直至处于相对恒定状态;当雨水入渗引起地下水位线抬升时,路堤的瞬态稳定安全系数将大幅降低;初始地下水位线越高,路堤的瞬态稳定性受降雨入渗影响而衰减的趋势越明显;当软弱地基的坡度较大或软弱土层较厚时,虽然路堤的瞬态稳定性受降雨的影响相对较小,但因路堤的初始稳定安全系数偏低,故仍需特别注意降雨条件下路堤的瞬态稳定性;路堤的入渗防护措施受到较小破坏时,也会大幅降低路堤的稳定安全系数。

Based on Fredlund＇s two stress state variables theory for unsaturated soil, combined transient saturated-unsaturated seepage finite element method with limit equilibrium method, the SEEP/W module and SLOPE/W module of GeoStudio software were used to analyze the transient stability of embankment over sloped weak ground subjected to rainfall condition. Results show that the stability safety factor of embankment over sloped weak ground presents an approximately linear decrease trend with the decrease of the suctional strength of embankment soil and soft soil. The greater is the rainfall intensity, the higher is the decrease rate of embankment stability safety factor during and after rainfall. Embankment stability safety factor continuously decreases to a relatively constant value as the increase of rainfall duration. When rainwater infiltrates to water table and leads to water level rise, embankment stability safety factor will decrease dramatically. The higher is the initial water level, the more significant is the decrease of embank- ment transient stability influenced by rainfall infiltration. When the gradient of weak ground is larger or the thickness of soft soil layer is thicker, the embankment transient stability affected by rainfall is relatively small, but special attention should be paid to the transient stability of embankment subjected to rainfall condition because of the lower initial stability safety factor. The minor damage of protection measures for embankment infiltration will greatly reduce the stability safety factor of embankment.