弱透水层深度对深厚覆盖层坝基渗控的影响研究

摘要

Monolayer, continuous and equal thickness weak aquifer usually exists at different depth of dam foundation with thick overburden layer, it is necessary to combine the cut-off wall with weak aquifers to form a unified seepage prevention sys-tem. Aiming at the thick overburden layer of dual-structure consisted of strong and weak aquifers, we analyze seepage discharge at dam foundation, the seepage gradient at water evolution points and cut-off wall bottom by seep/w, and study the relation be-tween dam foundation seepage and the depth of weak aquifer. It is found that for the dam foundation without cut-off wall, the shallower the weak aquifer is, the smaller the seepage discharge and gradient are;the seepage control under deeper weak aquifer would be more difficult. When the cut-off wall is set, the cut-off wall and the deeper weak aquifer formed a combined seepage system, which can better reduce seepage discharge and resist the seepage gradient, compared with the closed combined seepage system at shallower part. The weak aquifer in thick overburden layer can effectively reduce the cost of seepage prevention meas-ures, the simulation results can provide reference for seepage prevention in strong and weak interbedded dam foundation.%在深厚覆盖层坝基中不同深度处常含有单层、连续、等厚弱透水层，如何将防渗墙和弱透水层优化结合形成联合防渗体以减小防渗体的深度，值得深入探讨。采用Seep/w软件分析了强、弱透水层二元结构深厚覆盖层坝基的渗流量、出逸坡降、防渗墙底部坡降，探讨了不同深度处的弱透水层对坝基渗流影响的规律。研究发现，坝基中未设置垂直防渗墙时，弱透水层所处的位置越浅，越能有效降低渗流量、抑制坝基坡降；弱透水层所处的位置较深时，对大坝掺控则不利。坝基中设置垂直防渗墙时，较深的弱透水层与防渗墙形成的封闭式联合防渗体系，相比较浅的封闭式联合防渗体系，更能有效降低渗流量、抑制坝基出逸坡降。深厚覆盖层中弱透水层的存在能有效降低坝基控渗的成本。研究成果可为强弱透水互层的坝基掺控方案确定提供参考依据。