胶凝砂砾石坝抗震特性及其地震作用计算方法

Seismic behavior of Cement-Sand-Gravel dam and the calculation method of its seismic loads

胶凝砂砾石坝具有独特的结构型式,且由低强度材料填筑而成,因此其动力特性和抗震性能具有独自的特征。采用时程动力法,计算分析了胶凝砂砾石坝的动力特性及地震响应规律,探讨了坝体材料、基岩刚度以及坝高变化对该类大坝地震动力响应的影响规律。研究结果表明,与同等高度混凝土重力坝相比这种坝的地震动力响应明显较小,即使在强震作用下,坝体地震动应力仍处于较低水平;胶凝砂砾石坝具有明显不同于重力坝的动力特性和地震响应规律,按现有重力坝拟静力法不能正确计算胶凝砂砾石坝的地震作用效应。在大量分析成果的基础上,研究提出适用于该坝的地震动态分布系数和动水压力分布系数计算方法,可方便用于坝体地震惯性力和坝面动水压力的计算,为采用拟静力法进行该坝抗震设计工作提供了参考依据。

As a new type of dam with Symmetric trapezoidal cross section, Cement-Sand-Gravel（CSG）dam is built up with CSG material, so its seismic resistance and dynamic characteristics are unique. Tostudy its seismic safety, time history analysis method is taken in this paper. Based on FEM, the dynamiccharacteristics and seismic response of CSG dam are analyzed. The effects of stiffness of dam and bedrockand height of dam on its seismic responses are studied. The results show that the seismic responses of thisdam are evident low compared with concrete gravity dam, and the seismic stresses within dam are notlarge enough to endanger dam safety even during strong earthquake. This type of dam has different seismicresponse and dynamic characteristic with gravity dam,so the calculation method of seismic loads for gravi-ty dam cannot deal with CSG dam well. Based upon FEM analysis results,the methods for estimating seis-mic distribution coefficient and the hydrodynamic pressure coefficient, which is suitable for this new typeof dam, are proposed to calculate the seismic loads and hydrodynamic pressure on this dam. The conclu-sions of this paper can provide reference for aseismic design of CSG dam.