重力坝沿建基面失稳破坏的真实安全度研究

采用强度储备系数法，对重力坝建基面破坏过程进行非线性有限元模拟，并分析了坝体地基弹性模量比和建基面应力分布状态对破坏过程和强度储备系数的影响。研究结果表明：破坏过程可划分为4个阶段：贯通率平稳期、加速期、短暂平稳过渡期、急剧增加失稳期。当弹性模量比一定时，应力状态越趋于均匀分布，大坝处于稳定状态时的强度储备系数越大，坝趾坝踵处的应力比值越大，大坝处于稳定时的强度储备系数越小；当建基面应力分布状态一定时，弹性模量比的变化不改变建基面的总体破坏特征，强度储备系数与弹性模量比成正比。综合考虑应力分布及弹性模量比的影响，给出了正常荷载作用下重力坝沿建基面失稳破坏的真实安全度取值范围为1．5～2．5。

Study of true safety degree of failure along foundation surface of gravity dam

Strength reserve coefficient method based on nonlinear FEM is adopted to analyze the failure process of gravity dam along the foundation surface. Meanwhile, the influences of elastic modulus ratio of dam to foundation and stress distribution along foundation surface on the failure process and strength reserve coefficient (SRC) are studied. The results indicate that the failure process can fall into four periods: smooth connectivity period, acceleration period, short smooth transition, sharp accelerating failure period. With a constant elastic modulus ratio of dam to foundation, the more uniform the stress distribution is, the greater SRC is. The greater the ratio of stress at dam’s toe to dam’s heel is, the smaller SRC is. When stress distribution along foundation surface is invariable, the variation of elastic modulus ratio does not affect the overall failure feature of the foundation surface and the SRC is in proportion with the elastic modulus ratio. Finally, the true safety degree at the range of 1.5－2.5 is proposed for the failure evaluation of gravity dam along the foundation surface under normal loads.