深厚覆盖层中新型扩底防渗墙对防渗效果的影响

Influence of a new cutoff wall of expanded base type on the seepage controlling in deep overburden foundation

为降低防渗墙端部的渗透坡降,提出改变防渗墙端部局部的结构形式,将常规长方体结构形式改为新型扩底结构形式,并对比分析了常规结构形式和扩底结构形式防渗墙端部渗透坡降的分布规律。研究表明:与常规结构形式相比,扩底结构形式能够显著降低防渗墙端部和下游坝脚出溢处的最大坡降;扩底结构的半径越大,防渗墙端部的最大渗透坡降越小,下游坝脚出溢处的最大渗透坡降越小;对于概化模型,常规结构形式防渗墙贯入深度为35 m时,防渗墙端部最大坡降为0.85,下游坝脚处最大渗透坡降为0.27,要达到相同防渗效果,半径1.5 m的扩底结构形式防渗墙的贯入深度仅需23 m;扩底结构形式显著优于常规形式,它能够大幅度降低防渗墙建设的工程量和工程造价,显著缩短防渗墙施工工期。

The hydraulic gradient at the bottom of cutoff wall in a deep overburden foundation is large,and may cause the local seepage failure near the bottom of cutoff wall,which may induce the differential settlement and crack of anti-seepage structure threatening the dam safety.In order to reduce the hydraulic gradient at the bottom of cutoff wall,a new cutoff wall of expanded base type was proposed to change the local structure type of the cutoff wall tip.The distributions of the hydraulic gradient at the bottom of cutoff wall were compared and analyzed with different types of local structure.The results show that the expanded base structure could significantly reduce the maximum hydraulic gradient at the bottom of cutoff wall and the maximum hydraulic gradient at the downstream side;the larger the radius of expanded base structure was,the smaller the maximum hydraulic gradient was.For the generalized model,when the penetration depth of cutoff wall with the conventional type was 35m,the maximum hydraulic gradient at the bottom of cutoff wall was 0.85,and the maximum hydraulic gradient at the downstream side was 0.27.For the cutoff wall of expanded base type with a radius of 1.5m,in order to achieve the same anti-seepage effect,the penetration depth was only 23 m.It can be seen that the type of a expanded base structure was significantly superior to the conventional type.It can significantly reduce the construction quantity,the investment,and the construction period of cutoff wall.