考虑高压水劈裂的高重力坝安全性试验研究

Research on the safety of high gravity dams considering hydraulic fracturing

高压水劈裂是高水压驱动裂缝扩展的一种现象,常是影响涉水工程安全的一大因素。由于高坝需抵挡巨大水头,且混凝土坝具有"无坝不裂"的特性,高压水劈裂也逐渐成为高混凝土坝安全研究的重要内容。为了评价高压水劈裂对混凝土重力坝的影响,本文针对重力坝上游面水平裂缝设计了高压水劈裂试验,并参照重力坝可能承受的工况进行了系列试验,讨论了混凝土强度和应力状态对高压水劈裂的影响。根据试验结果,对有限元模型进行了校核,并用此模型计算了3种不同准则设计的重力坝在高压水劈裂方面的差异。分析表明,目前准则在设计200 m以上重力坝时可能存在高压水劈裂风险,且不同国家的准则对高压水劈裂影响较大,具体优化方案还需对坝体的应力指标进行深入研究。

Hydraulic fracturing is a phenomenon in which crack is fractured by a pressurized liquid. It isoften a factor influencing the safety of hydraulic structures. This study presents a test method to evaluatethe safety of high concrete gravity dams in the presence of hydraulic fracturing. A large concrete specimenwith embedded crack was designed according to the stress condition of gravity dam heel, and a series oftests at various concrete ages and under different uniaxial stress conditions were performed. The influenceof concrete strength and stress on the test results was discussed. On the basis of the tests, a finite ele-ment method was developed to analyze the influence of hydraulic fracturing on high gravity dams. Further-more,safety of different dams designed by specifications in China,the USA and Switzerland was comparedwith the finite element method. It revealed that gravity dams higher than 200 m designed by current specifi-cations will be in risk considering hydraulic fracturing and dams designed by different specifications havesignificant differences in anti-hydraulic fracturing. The vertical compressive stress at the dam＇s upstream sur-face might be the key for improving the resistance of hydraulic fracturing. However, more studies need tobe conducted to quantify this indicator.