某大坝右岸防渗缺陷和新增防渗排水措施效果分析

Analysis on the impervious defect and new drainage measures for seepage control on the rightbank of a dam

某大坝是国内已建工程中覆盖层最深的,尤其是其右岸覆盖层最大深度达420 m。工程运行中发现右岸渗漏量较大,且右岸山坡地下水位整体偏高,局部山坡和排水廊道发生渗透破坏。结合工程现场检查情况和现有监测资料,对该大坝右岸渗流性状进行综合分析,分析渗水主要来源和途径、渗流稳定以及防渗系统存在的缺陷。根据现阶段右岸出现的问题,初拟两种防渗系统延长方式及新增排水廊道的处理方案,运用有限元对渗流场进行计算,对比分析两种初拟方案对减少渗漏量和降低地下水位的效果。结果表明在0+610~0+710底部新增封闭式防渗墙与帷幕灌浆,能有效减少渗漏量并能降低防渗系统右端沿线的水头,新增排水廊道排水孔能有效降低排水廊道附近的水头,对右岸边坡渗透稳定有利。所以,截渗与导排相结合是较为有效的防渗处理措施。

The overburden of a dam is the deepest in China, whose maximum depth ot the right bank is 420 m. There is a large amount of leakage on the right bank during operation. The underground water level of right bank is high and seepage failure has occurred at the local hillside and the drainage gallery. Combining site inspection and the existing monitoring records, seepage character analysis is conducted. The main source, seepage path, seepage stability and defect are analyzed. Aiming at the problems of the right bank, two kinds of seepage control system and new drainage gallery is planned. As well, FEM is used to calculate the effect on reducing leakage and the underground water level. The calculation results show that the bottom of the new cut-off wall and curtain grouting in the section 0＋610-0＋710 can effec- tively reduce the leakage and the local water head, and the additional drainage holes can lower the water head of gallery, which is beneficial to the right bank slope stability.