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针对李家峡大坝6号坝段坝基扬压力产生异常的现象,建立了该坝及坝基的三维渗流有限元模型。详细介绍了模型中防渗帷幕及坝基、坝体排水孔模拟的方法,并且利用人工神经网络反演了岩体的渗透系数张量,对坝基进行了渗流有限元分析,分析不同防渗、排水以及基岩地质条件下的坝基渗流场,评估了各种因素对坝基渗流场的影响,结合坝基钻孔取芯、水质分析等试验成果,分析了扬压力异常的物理成因。研究结果表明,引起扬压力异常的原因是防渗帷幕局部存在缺陷,且帷幕前浅部岩层存在强透水带。建议对右岸6号坝段坝基进行灌浆处理,以阻断渗漏通道,提高防渗帷幕的阻水效果,并加强对渗水的抽排工作,以有效地降低扬压力。
Aiming at the abnormal phenomenon of the uplift pressure of dam foundation of No.6 dam section in Lijiaxia Dam, a three-dimensional finite element model of seepage dam and dam foundation is established. The method of simulating seepage prevention curtain and dam foundation and dam drainage hole in the model is introduced in detail. The permeability coefficient tensor of the rock mass is retrieved by artificial neural network, and the seepage finite element analysis of the dam foundation is conducted. As well as the seepage field of foundation under geologic condition of base rock, the influence of various factors on seepage field of dam foundation is evaluated. Combined with the test results of coring of core of dam foundation and water quality analysis, the physical causes of uplift anomaly are analyzed. The results show that the cause of the abnormal upward pressure is due to the partial imperfections of the curtain and the presence of strong permeable belt in the shallow fore part of the curtain. It is suggested to grout the dam foundation on the right bank of Dam 6 so as to block the seepage channel, improve the water blocking effect of the seepage curtain, and enhance the drainage work on seepage water so as to effectively reduce the uplift pressure.