白鹤滩水电站坝基排水廊道施工期涌水成因分析

A Causal Analysis of Water Gushing in the Foundation Drainage Gallery during the Construction Period in Baihetan Hydropower Station

白鹤滩水电站坝区地质条件复杂,发育有多条横穿上下游的层间错动带及断层,左岸及河床P2β3地层内存在裂隙发育柱状节理玄武岩,地下水埋藏分布复杂,坝区渗流状态复杂。2020年5月中旬,17号、18号坝段基础排水廊道排水孔施工完成后产生涌水,最大涌水量达410 L/min。现场取样进行水化学分析,并追踪涌水量变化情况,参照近期水文气象资料,结合前期工程及水文地质资料,对涌水来源及涌水渗漏通道进行了综合分析,确认左岸山体深部裂隙水为涌水主要来源,P_(2)β_(3)地层内第一、二类柱状节理玄武岩与C_(2)、C_(3)、C_(3-1)等结构面为主要渗漏通道,据此为大坝蓄水过程及正常运行阶段坝区渗流状态监测布置提供建议。

The interlayer staggered zones and faults are widely distributed in Baihetan Hydropower Station in Jinsha River Basin,China.The columnar joints basalts found in left bank and riverbed are abundant in fissures.Complex distribution of groundwater table perplexes the seep⁃age state of the dam site area.In late May 2020,water gushed in the foundation drainage galleries of 17&18#dam sections,with maximum gush of water up to 410 L/min.On-site sampling for hydro-chemistry analysis,tracking changes of gush water amount,referring to hydrologi⁃cal data of recent months and consulting previous engineering geology datum and hydro-geological data are done for comprehensive analysis of gush water sources and gush water leakage paths,which confirms that deep fissures water in the left bank is the main gushing water source.The columnar arthritic basalts in the P_(2)β_(3) rock formation,and layers C_(2),C_(3),C_(3-1) are the main leakage paths.Proposals are offered for arrang⁃ing seepage state monitoring during impoundment and normal operation stages with reference to this conclusion.