施工期水电站坝址环境水化学特征研究及其意义——以向家坝水电站为例

Study on damsite groundwater chemistry during construction and its significance, a case of Xiangjiaba dam

处于施工期的水电站往往缺乏足够的渗流宏观原型监测资料,此可通过其微观动态——水质特征的分析以反映施工过程中区内地质体的水文地质特性以及坝基、坝肩等不同部位处帷幕的防渗性能。本文以向家坝水电站为例,在对不同位置水样进行水化学分析的基础上,首先采用水化学图示法定性地反映各部位的水质特征,然后利用系统聚类方法对各水样点进行划分从而得到4个族群,并对各族群内的水质指标进行统计分析;最后,应用PHREEQC软件进行反向模拟,计算获得坝址渗流过程中各类矿物溶解/沉淀的量及不同渗漏水源所占的比例,从而达到定量解析水—岩相互作用的目的。通过综合应用水文地球化学的各类方法,可以弥补在建工程原型监测资料短缺的困难,达到了解施工期坝址渗漏水体的来源以及评价对大坝基础潜在影响的目的,从而为后续的施工提供科学指导。

For the lack of macro prototype monitoring data during construction of a hydropower station, water quality as one of seepage micro regimes can be used to reflect hydrogeology features and anti-seepage effect of an impervious curtain concerned. The Xiangjiaba dam was taken as a case and its groundwater samples were collected and analyzed. First, a qualitative evaluation of water quality characteristics at different dam sections was shown by using hydrochemistry diagrams, and then saturation indexes were calculated for each of the four major location groups divided by a hierarchical cluster analysis. Last, inverse geochemical models of the groups were developed using PHREEQC to elucidate the dissolution or precipitation quality of different minerals and the percentage of different seepage sources. The conclusion is that the hydrogeochemical methods previously described, both qualitatively and quantitatively, are useful for revealing the seepage behaviors around the damsite during construction.