高面板坝土工格栅加固机制及抗震加固效果分析

Reinforcement mechanism and seismic evaluation of reinforced high CFRD with geogrid

现有土石坝震害调查、模型试验以及动力反应分析等研究结果表明,靠近坝顶区的上部坝坡是土石坝抗震的薄弱部位。目前强震区高土石坝抗震设计多采用土工格栅来加固上部坝坡,以提高坝顶区抗震稳定性,如何合理评价土工格栅的加固效果是国内外学者关注的焦点。本文在系统总结土工格栅加固机理的基础上,基于准黏聚力加固机理和等效复合体计算模型模拟土工格栅加固作用,从坝坡抗震稳定、坝体地震永久变形和面板防渗体系安全等方面对土工格栅加固高面板坝的加固机制及抗震加固效果进行了综合分析评价。结果表明:(1)格栅和堆石料的相互作用使得堆石料具有了一定的整体性,其刚度和强度均有一定程度的提高;(2)格栅加固可以限制堆石体侧向移动,提高坝坡整体性和稳定性,减少坝体地震永久变形,从而改善面板应力分布和减少面板接缝位移,提高防渗系统的安全性;(3)土工格栅对高面板坝具有综合的加固效果,需要采用综合性评价方法进行总体评价。

Based on the seismic investigations,shaking table model tests and dynamic response analyses of earth-rock dams,the greatest weakness of high concreted faced rock-fill dam subjected to strong earthquake loading usually locate at the upper slope near the dam crest.Although,the geogrid reinforcement techniques have been widely adopted in dam seismic design,how to evaluate reasonably the effect of geogrid in seismic reinforced high CFRD under seismic loading is still unclear.In this paper,based on the systematically summarizes of the reinforcement mechanism of geogird,pseudo-cohesion concept and the equivalent compound model,which was used to simulate geogrid reinforcement effect,the key factors including the slope stability,earthquake-induced settlement and the safety of impervious body are considered to evaluate the safety of reinforced CFRD with geogrid.The studies show:(1)the interaction between the geogrid and gravel makes the reinforced rockfill material have some degree of continuity,and can enhance its stiffness and strength.(2)The reduced lateral displacement and settlement,improvement of dam slope stability and stress distribution of concrete face-slab,can be achieved.(3)Geogrids have comprehensive reinforcement effect on high CFRD.It is necessary to use appropriate comprehensive method to evaluate its reinforcement effect.