面板砂砾石坝异常状态渗流计算及稳定分析

运用非饱和土渗流与强度理论,把渗流计算的水力条件用于边坡稳定分析之中,对沟后面板砂砾石坝进行了渗流场分析与边坡稳定计算,得到一些新的结论,可补充以前相关的研究结果。计算结果表明:坝料填筑分离造成的渗透各向异性尽管使浸润线升高,但是由于水平排水能力的提高反而使坝体的孔隙水压力总体上降低,从而也就提高了边坡的抗滑稳定安全性;当顶部面板与坝体脱开并导致异常状态渗流时,坝体顶部有一饱和区并且渗流出逸点很高,但坝体中部仍未饱和,异常状态渗流增加的孔隙水压力有限,对坝坡的抗滑稳定影响也很小,因此,按照最高浸润线的位置确定孔隙水压力进行抗滑稳定计算会导致错误的结果;坝顶异常状态渗流增加的孔隙水压力并不会导致下游坝坡滑动失稳,而坝体顶部渗透破坏会导致局部坍塌,最终发生溃坝事故。

The Analysis on the Abnormal Seepage and Stability in a Faced Rockfill Dam

The seepage and stability analyses for Gouhou faced rockfill dam was conducted using unsaturated soil seepage and strength theory.In the calculation,the hydraulic condition of seepage computation had been used in the stability analysis.The new conclusion provided a reference and complement for the former related research.The conclusion were: the hydraulic anisotropy caused by stratification elevates the height of phreatic table in case of steady seepage,however the safety factor will increase because of horizontal drainage.When the crack between the face and the material resulted in an abnormal seepage,the flow exited from the top of the dam,the top of the dam also was saturated,however the unsaturated zone still existed in the middle of the dam,the additional value of pore water pressure would not affect the slope stability so much.If the pore pressure was determined by the highest phreatic table as hydrostatic pressure,the stability analysis would obtain a wrong result.According to the calculation result of seepage and stability,the additional pore pressure from abnormal seepage would not lead to downstream slope failure,while the seepage failure on the top of the dam caused a local collapse and resulted in the breach at last.