基于饱和多孔介质PSBFEM的闸坝—可液化地基动力响应分析

Dynamic Response Analysis of Sluice Dam-liquefiable Foundation Based on PSBFEM with Saturated Porous Media

近年来我国水利工程选址地质条件复杂,深厚覆盖层上建坝已难以避让,闸坝抗震设计与安评的难度显著提高,尤其对于覆盖层中存在可液化土层的情况,有关研究较少,不利于准确把握与评价闸坝的动力响应和抗震性能.本文引入高效四分树方法,建立了闸坝-可液化地基体系的跨尺度分析模型,同时采用饱和多孔介质多边形比例边界有限单元和土体广义塑性模型以模拟地基孔隙水压力的产生、扩散和消散过程,精确地分析了体系的动力反应.结果表明:闸坝底部土体液化程度低于上下游地基土;闸坝呈整体向下游水平移动,并略有向下游倾斜的趋势;地震致使部分土体弱化,加剧了闸坝及防渗墙的变形,应采取适当的加固措施,避免影响机组安全运行.本文方法更加准确地反映了实际情况,且适应性强,为地基抗液化措施的对比与验证研究提供了可靠的技术支持.

In recent years,the geological conditions of water conservancy project site selection are complex in China,and it is difficult to avoid dam constructed on deep overburden.The difficulty of seismic design and safety assessment of gate dam is significantly increased.Especially for the situation of liquefiable soil layer in overburden layer,the relevant research is few,which is not conducive to the evaluation of the seismic performance of the dam.In this paper,an efficient quadtree cross-scale method is introduced to establish an analytical model of the dam and foundation system.The generation,diffusion and dissipation of pore water pressure are calculated by using the polygonal scaled boundary finite element method of saturated porous media and the generalized plastic model of soil,and the dynamic response of the system is analyzed accurately.The results show that the liquefaction degree of the soil at the bottom of the dam is lower than that of the foundation soil at the upstream and downstream;the dam moves horizontally downstream as a whole,and inclines slightly to the downstream.The soil is weakened due to the earthquake,resulting in an obvious deformation of the cut-off wall and the dam.Appropriate reinforcement measures should be taken to ensure the safe operation of the structures.The method in this paper reflects the actual situation more accurately and has strong adaptability,which provides reliable technical support for the comparison and verification of anti-liquefaction measures of foundation.