坝基两道防渗墙水头分担情况有限元分析

深覆盖层坝址上的高心墙堆石坝，在河床覆盖层中常设置两道混凝土防渗墙防渗。采用开发的有限元软件，参照砂卵石覆盖层深度近50 m的某心墙堆石坝工程的情况，分析了主、副防渗墙6种设置方案中坝基的稳定渗流场，得到了主墙、副墙和覆盖层的水头分担比例。所有方案中河床覆盖层上的水头都小于3 %。当主、副两道墙下部灌浆情况相同、端部之间设置灌浆帷幕封堵绕渗时，副墙承担的水头接近主墙；如果取消封堵绕渗的帷幕，副墙承担的水头下降到总水头的20 %～30 %；而副墙底部和主、副墙两端均不设帷幕的情况，副墙上承担的水头比例下降到总水头的8 %～11 %。副墙位于主墙的下游侧时，其上承担的水头比例比副墙位于主墙上游侧的情况略高。防渗墙承担的水头比例取决于墙整体的防渗能力，而对防渗墙本身的厚度变化不敏感。

FEM Analysis on hydraulic head ratio on the two diaphram walls under a dam

Two diaphram walls are frequently used in the rock-filled wall with a high core on the rock cover. Referring to the condition of a certain high rock-filled core dam with a nearly 50 m deep gravel-sand overburden, the steady seepage fields of the dam base in 6 set-up schemes of diaphram walls are analyzed using the finite element software developed by the first author, and the ratio of the hydraulic head acting on the main wall, secondary wall and gravel-sand layers in each scheme is obtained. The hydraulic head acting on the gravel-sand layers is less than 3 percent of the total in these schemes. In the schemes in which the water-tight curtain under the secondary wall is the same as that under the main wall and the round seepage between the two walls is blocked by the side water-tight curtains, the hydraulic head acting on the secondary wall is only slightly less than that on the main wall. If the side curtains are omitted, the hydraulic head on the secondary wall is only 20 percent to 30 percent of the total. If the curtain under the secondary wall is further canceled, the hydraulic head on the secondary wall will be decreased to 8 percent to 11 percent of the total. The hydraulic head on the secondary wall in the upstream side of the main wall is less than that in the downstream side. The hydraulic head ratio of the two walls is not sensitive to their thickness.