基于VOF法的碾压混凝土坝自由渗流场数值模拟

Numerical simulation of free seepage field in RCC dams based on VOF method

碾压混凝土坝渗流属于有浸润面的自由渗流,如何准确地确定浸润面位置是自由渗流场分析的关键及难点。同时,目前大坝渗流研究中多对地质条件、坝体细节以及排水孔进行较大程度的简化处理。针对上述问题,本文建立了包含不同地层、不良地质体、帷幕、排水孔以及坝体的碾压混凝土坝三维统一模型,采用耦合VOF法的三维非稳态水气两相流渗流模型,实现了对碾压混凝土坝复杂自由渗流场的数值模拟。运用该模型模拟某水电站碾压混凝土坝段正常蓄水位下的渗流场,结果表明:防渗帷幕和排水孔能够有效地改善渗流场分布,渗流控制作用明显;上游帷幕处的水力梯度最大值达到32.64,可能会对帷幕造成破坏,应引起足够重视。最后将现场监测点水头和排水孔出水量的模拟值与现场实测值进行对比,平均误差分别为1.57%和8.70%,模拟值与现场实测值基本吻合,验证了该模型的可靠性。

Seepage in roller compacted concrete （RCC） dams is the free seepage with saturated surface, and how to accurately determine the position of saturated surface is the key and difficulty in the analysis of the free seepage field. Meanwhile, the geological conditions, the details of the dam and the drainage holes are generally simplified significantly in the seepage research at present. Aiming at these problems, a three-dimensional unified model of RCC dam, included formations, unfavorable geological body, curtains, drainage holes and dam body, was firstly established in this paper. Then, coupled with the volume of fluid （VOF） method, a three-dimensional seepage mathematical model of air-water two-phase flow was devel- oped to achieve the numerical simulation of the complicated free seepage field in RCC dam. Finally, a RCC dam section of a hydropower station was taken as a case. The results showed that the curtains and the drainage holes could improve the distribution of seepage field effectively, and the hydraulic gradient in the upstream curtain reached a maximum value of 32.64, threatening the curtain＇s security, to which enough attention should be paid. Furthermore, comparing the simulation value with the measuring value of the head and the water yield, the average errors were 1.57 % and 8.70 % respectively, which verified the reliability of the method.