地震作用下金沙江某跨江桥梁岩质岸坡动力响应分析

Dynamic Response Analysis of Rock Bank Slope of a Bridge Across Jinsha River Under Earthquakes

由于地震波的随机性及地质构造的复杂性,导致岩质边坡的地震响应特征变得十分复杂。以金沙江地区某跨江桥梁岩质岸坡为例,采用有限元方法研究了地震波在岩质边坡内的传播特征,分析了不同类型结构面对边坡动力响应特征的影响;采用振动台模型试验验证了数值计算结果,探究了边坡的动力变形演化规律及其破坏机制。研究结果表明:软弱结构面对岩质边坡的波传播特征影响较大,在波传播过程中结构面使坡内出现局部的放大效应,相同条件下边坡的动力放大效应为:块状边坡>顺层边坡>反倾边坡;边坡高程、坡表微地貌及结构面对边坡的动力放大效应具有较大的影响,边坡动力放大系数随高程增加而增加,坡表微地貌变化使平台区域出现局部放大现象,块状边坡中放大效应主要集中于最上层顺向结构面以上的表层坡体;地震作用下块状边坡的动力放大效应随激震强度的增加而增加,边坡动力变形演化过程主要包括弹性变形、塑性变形和滑动破坏3个阶段;软弱结构面对块状边坡的地震破坏模式具有控制性作用,最上层顺向结构面为潜在滑面,其地震破坏模式为拉裂—滑移—倾覆式破坏。

Due to the randomness of seismic waves and the complexity of geological structure,the seismic dynamic response characteristics of rock slopes become very complicated.Taking a rocky bank slope of a bridge across the Jinsha River as an example,the propagation characteristics of seismic waves in rock slope were studied by using finite element method(FEM),and the influence of different types of structural planes on the dynamic response characteristics of slopes was analyzed.Shaking table model test was used to verify the numerical results,and the dynamic deformation failure evolution law and failure mechanism of the slope were deeply investigated.The propagation characteristics of seismic waves in rock slope were studied by using FEM,and the dynamic deformation evolution law and failure mechanism of the slope were analyzed.The results showed that weak structural plane had a great influence on the wave propagation characteristics of slopes.In the wave propagation process,structural plane caused local amplification effect in the slopes.Under the same conditions,the dynamic amplification effect of the slopes is as follows:block slope>bedding slope>anti-dip slope.Slope elevation,surface microtopography and structural planes had a great influence on the dynamic amplification effect of slopes.The dynamic amplification coefficient of the slopes increased with the elevation,and the variation of the slope surface microtopography resulted in the phenomenon of local amplification at the platform area.The amplification effect in the block slope was mainly concentrated on the surface slope above the topmost bedding structural plane.Under the action of earthquake,the dynamic amplification effect of the block slope increased with the increase of the seismic intensity.The evolution process of dynamic deformation of the block slope mainly included three stages:elastic deformation,plastic deformation and sliding failure.Weak structural plane had a controlling effect on the seismic failure mode of massive slope,and the topmost structural plane was the potential sliding surface,and its seismic failure mode was split—slip—overturning failure.