深厚覆盖层坝基防渗墙地震反应规律研究

为探讨深厚覆盖层中坝基防渗墙地震反应规律并评价其抗震安全性,以金平堆石坝为工程背景,在三维非线性静力分析基础上,采用子模型技术对坝基防渗墙进行了地震动力时程分析,坝体材料及覆盖层采用Hardin-Drnevich动力本构模型,防渗墙与覆盖层的接触关系采用薄层接触单元模拟。计算成果表明：防渗墙上部靠两岸侧动应力反应较大,动静叠加后其应力变形规律相对静力工况变化较小；受深窄河谷及右岸折坡地形影响,竖直向压应力极值并未如一般规律所反映的出现在墙体中下部,而是位于墙身中上部的右岸侧折坡处；在设计地震作用下,防渗墙拉裂状况基本没有恶化,压应力极值增幅仅3.5%。综合来看,设计地震对防渗墙的运行状态影响不大。

Features of Seismic Response of Cutoff Wall in Dam Foundation with Deep Overburden

The present research is to explore the seismic response features of the cutoff wall in dam foundation with deep overburden and to evaluate its seismic safety. Jinping rockfill dam was taken a case study. On the basis of 3-dimensional nonlinear static analysis, submodeling method was used to carry out time-history analysis on the foundation’s cutoff wall. The filling materials of dam and the alluvium deposit were simulated by Hardin-Drnevich dynamic constitutive model. The thin-layer contact element was used to simulate the contact relationship between the cutoff wall and the overburden. Results indicated that dynamic stresses showed a strong response in the upper part of the cutoff wall near the bank sides. After superposing the dynamic response with static response, the deformation and stress distribution rules changed slightly compared with those in the static state. Influenced by the terrain of deep and narrow valley and the turning point of the right bank, the vertical compressive stress extremum occurred in the turning point of the right bank of the mid-upper part of the wall instead of the mid-lower part as general rule shows. During the seismic history, the rupture area of the cutoff wall extended little, and the growth rate of vertical compressive stress extremum was only 3.5%. In conclusion, the influence of seismic load on the work condition of cutoff wall was not obvious.