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本文采用二维有效应力动力分析方法分析了1976年7月28日唐山地震时密云水库白河主坝斜墙砂砾石保护层滑落的原因。文中对于计算模式和计算方法也作了较系统的阐述。用等参数静力有限单元法计算了白河主坝的非线性静应力,用等参数动力有限单元法计算了非线性动应力、反应加速度、振动孔隙水压力的产生、扩散和消散过程及其不同时刻的分布规律、地震引起的沉降(残余垂直位移)及其与时间的关系。最后,结合算出的孔隙水压力对保护层作了一般的稳定分析。分析结果指明,白河主坝砂砾石保护层滑落的原因是:在地震剪应力作用下保护层内积累了大量的残余孔隙水压力,导致保护层与斜墙接触面的有效应力减小,抗剪强度大量降低之故。
In this paper, two-dimensional effective stress dynamic analysis method was used to analyze the reason why the gravel protective layer slipped on the inclined wall of the main dam of Baihe River in Miyun Reservoir on July 28, 1976, Tangshan earthquake. The article also made a systematic exposition of the calculation mode and calculation method. The static finite element method is used to calculate the nonlinear static stress of the main dam of Baihe River. The dynamic stress, reaction acceleration, generation and propagation of the dynamic pore water pressure and their dispersion are calculated by the equivalent finite element method The distribution law of time, the settlement caused by earthquake (residual vertical displacement) and its relation with time. Finally, a general stability analysis of the protective layer is made based on the calculated pore water pressure. The analysis results indicate that the reason why the gravel protective layer of the main dam of the Baihe River slipped off is that a large amount of residual pore water pressure accumulates in the protective layer under the shear stress of the earthquake and the effective stress at the contact surface between the protective layer and the inclined wall decreases. The intensity is reduced a lot.