地震荷载作用下非饱和土边坡稳定性数值模拟

Numerical simulation of stability of unsaturated soil slopes under earthquakes

以非饱和土土水特征曲线为依据,建立了可同时考虑基质吸力与体积含水率影响的非饱和土强度公式,进而以非饱和土广义黏聚力和饱和土的内摩擦角为强度参数,将强度折减有限元理论推广到了非饱和土边坡的稳定性分析中。在短时地震荷载作用时间段内不考虑非饱和土含水率(或饱和度)与基质吸力变化的前提下,采用黏弹性人工边界模拟地基辐射阻尼的影响,建立了基于静动力有限元的非饱和土边坡地震稳定性简化分析方法,并以有限元数值计算、关键点相对位移时程曲线是否收敛和塑性区分布分别探讨了非饱和土边坡的地震稳定性。分析结果显示基质吸力虽然对非饱和土边坡的静力稳定性影响显著,但地震作用力仍然在边坡的地震稳定性分析中起主导作用。

Based on the soil-water characteristic curve of unsaturated soils, a new formula for strength of unsaturated soils taking into account the influence of matric suction and volumetric water content simultaneously is established. The strength reduction FEM is introduced into the stability analysis of unsaturated soil slopes in which the generalized cohesion of unsaturated soils and internal friction angle of saturated soils are adopted as strength parameters. Without considering the change of water content(or saturation) and matric suction under short-term seismic loading, a static and dynamic finite element method for analyzing the seismic stability of unsaturated soil slopes is established. The effect of foundation radiation damping on seismic response is simulated by combing viscoelastic artificial boundary. The seismic stability analysis is validated through numerical simulations in which the finite element calculation, convergence of time-history of relative displacement on key points and plastic zone distribution are used to judge the dynamic stability of the slopes. The analyses show that although the matric suction has significant effect on the static stability of unsaturated soil slopes, the earthquake force still plays a leading role in the seismic stability analysis of the slopes.