河谷地形对深覆盖层中防渗墙应力变形影响分析

为研究河谷地形对深厚覆盖层中防渗墙应力、变形的影响，以某沥青混凝土心墙堆石坝为工程背景，模拟了狭窄河谷和宽深河谷并分别建立有限元模型，坝体材料及覆盖层采用邓肯-张E-B模型，防渗墙与覆盖层、基岩之间的接触关系采用无厚度接触面模拟，进行三维非线性有限元计算，对比分析两种河谷情况下防渗墙的应力、变形情况。计算结果表明：狭窄河谷中，防渗墙沉降和水平向位移及防渗墙与覆盖层的不均匀变形均比宽深河谷小，其中不均匀变形最大减小了24.8%；宽深河谷中，防渗墙受河谷地形约束作用较弱，竖直向压应力较狭窄河谷更大，最大增加了40.3%；防渗墙的竖直向压应力最大值位置受中性点位置和河谷地形的共同影响，其中竖直向压应力最大值约30%来自墙顶坝体土压力，70%来自与覆盖层之间的负摩擦力。其研究结果可为不同地形条件下坝基防渗墙的设计提供参考。

Analysis of effect of canyon terrain on stress and displacement of cutoff wall in dam foundation with deep overburden

In order to research the effect of the canyon terrain on the stress and displacement of cutoff wall in dam foundation with deep overburden, taking an asphalt concrete core rockfill dam project as a background, a narrow canyon and a broad canyon were simulated and corresponding finite element models were also established respectively. The filling materials of dam and overburden were simulated by the Duncan-Chang E-B model. The interface without thickness was used to simulate the contact relation between the cutoff wall, overburden and bedrock. A 3-D nonlinear finite element calculation was carried out to analyze the stress and displacement of cutoff wall in different canyon terrains. Results indicate that vertical deformation and horizontal displacement of cutoff wall, as well as unequal settlement between cutoff wall and overburden in narrow canyon are less than that in a broad one; the maximum unequal settlement reduced 24.8%. The cutoff wall is less restrained by the broad canyon than that in a narrow one; thus the vertical stress in the broad canyon is greater and increases by 40.3% utmost. The position of the maximum vertical stress of cutoff wall is affected both by the position of neutral point and canyon terrain. The maximum vertical stress is approximately 30% by the weight of embankment and 70% by negative skin friction. The studied results can provide a reference for the design of cutoff wall in dam foundation in different canyon terrains.