水位下降对边(滑)坡稳定性的影响

通过PLAXIS有限元程序对一边坡算例进行分析,根据实际工程的需要选择理想弹塑性模型和莫尔-库仑屈服准则进行数值模拟,并对比分析了土体分别设置为排水条件和不排水条件时的情况。计算结果表明,当土体设置为排水条件时,在库水水位下降过程中,安全系数随水位的下降逐渐减小,但当水位下降了20 m以后,由于孔隙水压力给滑面提供了竖直方向的作用力,随着水位的继续下降安全系数反而略有上升。当土体设置为不排水条件时,坡体内产生的超孔隙水压力对边坡安全系数的降低更为明显。考虑坡体内超孔隙水压力时安全系数的计算结果比不考虑坡体内超孔隙水压力时的计算结果低10%左右,因此实际工程中应该充分考虑超孔隙水压力的积累和消散,并根据"最不利水位"所对应的安全系数进行校核。在计算过程中PLAXIS程序能较好地模拟水位下降引起的渗流作用对边(滑)坡稳定性的影响。

The Effect on Stability of Slope under Drawdown Conditions

The program of PLAXIS is adopted to analyse the slope stability.The ideal elastic-plastic model and the yield criterion of Mohr-Coulomb theory are simulated numerically for the realistic project.The drainage condition and undrained condition of the soil body are compared.The calculation shows that the safety factor declines with the drawdown of the water level under the drainage condition.However,the safety factor would rise after the water level drops by 20 meters,which is caused by the vertical acting force of the pore pressure,and its influence on the safety factor of the slope is more obvious under the undrained condition.The safety factor with the excess pore pressure is 10% lower than that without regard to the pressure.As a result,the accumulation and dissipation of the excess pore pressure should be taken into consideration in the practice.What's more,the safety factor should be checked according to the "least favorable water level".The program of PLAXIS can simulate the effect of seepage on the slope stability when the water level drawdown in calculation.