宝珠寺水电站廊道析出物中钙质成因分析

Analysis of the formation mechanism of the calcareous sludges from the drainage galleries in Baozhusi hydropower plant,Sichuan,China

大坝廊道排水孔析出物的产生是一个普遍现象,正确认识析出物的成因,是评价坝基渗透变形、坝基灌浆帷幕的工作状态的基础。析出物中的钙质一般有两个成因,其一是渗透库水自身的化学反应形成,其二是渗透库水对渗透途径上的岩体中的钙质成分或是对灌浆帷幕的溶蚀形成。若是后者,则标志着渗透库水对坝基、帷幕产生了溶蚀作用,这对坝基的稳定、帷幕的防渗作用将产生不利的影响。通过对析出物、坝前后不同深度库水取样的化学分析鉴定,坝基渗水通道的研究,以及对电站运行至今扬压力监测资料的分析,认为大坝廊道中钙质析出物是由于渗流库水脱硫酸作用促使HCO-3浓度升高而引发的渗流水中所含钙质析出的结果,而与坝基或帷幕的溶蚀无关,坝基以及灌浆帷幕中没有或基本没有发生渗透变形,钙质析出物的排出未损坏防渗帷幕体。

It is a general phenomenon that there are some sludges from the drain holes in drainage galleries of dams.To understand the causes of the sludges correctly is the basis of evaluating the seepage failure and the working state of grout curtains of a dam foundation.Usually,there are two mechanisms for the formation of calcareous sludges.One is the mechanism of the self chemical reaction of seepage water,and another is the dissolution mechanism of calcareous materials in dam foundation rocks or in grout curtains by seepage water.If the latter is confirmed,there is dissolution of calcareous materials in the dam foundation or grout curtains.This will exert an unfavorable influence on the dam foundation stability and seepage control of grout curtains.The authors analyze and determine the samples of the sludges and the water fetched from drainage galleries and various depths of water upstream and downstream the dam of Baozhusi hydropower plant in Sichuan,study seepage channels in the dam foundation and analyze the monitoring data of seepage discharge and uplift pressure collected since the operation of the plant.According to those studies,they believe that the calcareous sludges in drainage galleries in the dam of Baozhusi hydropower plant are formed by slugging of calcareous materials in the seepage water because of the increasing density of HCO-3 caused by the desulphurization of seepage water,and has nothing to do with the dissolution of calcareous materials in the dam foundation rocks or in the grout curtains.This study demonstrates that no chemical seepage failure happens in the dam foundation and grout curtains and the formation of the calcareous sludge does not damage the grout curtains.