地震作用下孔隙水压力对边坡动力稳定性的影响

以某水库堤坝为研究对象,研究了地震作用下孔隙水压力对边坡动力稳定性的影响。先分析地震荷载引起的渗流场时程变化,再与应力场进行耦合,分析坝坡稳定性。渗流场和震动场分析采用有限元法,坡体稳定性分析采用极限平衡法。结果表明:地震作用会激发超孔隙水压力的增长,是否考虑地震荷载和孔压变化的耦合效应会使得稳定性分析结果有较大差异。不考虑该耦合作用时,边坡易发生浅层滑动,滑动面较平坦,易高估堤坝的抗震稳定性;考虑该耦合作用时,滑面位置明显深入,易发生深层滑动。孔压的累积效应可能是两相介质边坡动力失稳的关键因素。因此,地震作用下孔隙水压力对边坡动力稳定性分析具有至关重要的作用。

Effect of Pore Water Pressure on Dynamic Stability of Slope under Seismic Action

The influence of pore water pressure on the dynamic stability of slope under seismic action is studied in this paper with a reservoir dam as research object. The temporal changes of seepage field caused by seismic load are analyzed first, and then the stability of dam slope is investigated by coupling the stress field with the seepage field. Finite element method is used to analyze seepage field and vibration field, while limit equilibrium method is used to analyze slope stability. Results demonstrate that seismic action stimulates the increase of excess pore water pressure, and whether to consider the coupling effect of seismic load and pore pressure change will make the results of stability analysis quite different. When the coupling effect is not considered, the slope is prone to shallow sliding, with flat sliding surface; as a result, the seismic stability of dam slope is overestimated. On the contrary, when the coupling effect is taken into account, the position of slip surface is obviously deeper, which easily leads to deep sliding. The cumulative effect of pore pressure may be the crucial factor of the dynamic instability of two-phase media slopes. In conclusion, pore water pressure under seismic action plays an important role in the analysis of slope dynamic stability.