存在高渗透区的黏土心墙土石坝渗流稳定性分析

黏土心墙土石坝是重要的挡水建筑物，心墙的低渗透性可以大幅降低坝体水力梯度，减少坝体发生渗透破坏的风险。然而心墙的质量问题（如局部高渗透区）会影响坝体的渗透稳定性，甚至酿成管涌溃坝等严重后果。以瀑布沟心墙土石坝为原型开展坝体渗流大型水槽模型试验，并结合有限元数值模拟方法研究高渗透区对坝体内部渗流场和渗流稳定性的影响。试验表明高渗透区域将改变心墙的渗流场，成为优势渗流通道，导致高渗透区域附近孔压值大幅上升，同时高渗透区域的存在将显著提升坝体渗漏速率。试验与模拟结果一致表明，随着高渗透区域逐步上移，高渗透区所在位置处的孔隙水压力增大，坝体渗漏量减小。高渗透区和心墙的渗透系数增加都会使心墙孔压值和渗漏量增加；随着高渗透区的渗透系数的增大，心墙坝渗流稳定性系数降低，导致坝体稳定性下降；随着心墙渗透系数的增大，高渗透区水力梯度略微减小，但心墙整体临界水力梯度下降，坝体稳定性降低。所得结论可为基于监测数据反演分析心墙的质量问题和评估坝体的安全性能提供依据。

Seepage stability analysis of earth and rockfill dam with clay core by considering high permeability zones

Rockfill dams with clay core are important water-retaining structures. The low permeability of the core wall can highly reduce the hydraulic gradient of the rest dam body and the risks of seepage failure to the dam body. However, the quality of the core wall (such as local high-permeability zones,) will affect the seepage stability of the dam body, which may lead to serious consequences such as piping failure. In this paper, large-scale water flume tests of seepage stability is performed with the prototype of the Pubugou soil and rockfill dam. A numerical model of finite element which was validated with the test results was used to study the influence of the high-permeability zone (HPZ) on the seepage field and stability of the model dam. The test shows that the HPZ will change the seepage field of the clay core and become a dominant seepage channel, and meanwhile, the existence of high permeability area will significantly increase the seepage rate of the dam body. The test and simulation results both show that the pore water pressure of the upper part of the clay core increased with the rising of the HPZ position; while the leakage volume of the dam decreased at the same time because of lower water pressure of the HPZ. With the increase of the permeability of the clay core and the HPZ, the pore water pressure of clay core and the leakage rate both increased. The seepage stability of the dam would be reduced with the increase of the permeability of the HPZ and the water level. Although the increase of the permeability of the clay core will leading to decrease of the hydraulic gradient in the HPZ,the increase of the hydraulic gradient in the clay core would lead to decrease of the seepage stability of the clay core. The results obtained in the paper offer basis on the back analysis of the clay wall quality and the assessment of the safety and performance of the dams.