深厚库底回填料上面板堆石坝动力反应分析

深厚库底回填料是影响面板堆石坝动力响应的重要因素之一。为深入研究深厚库底回填料对面板堆石坝动力响应的影响,基于某拟建抽水蓄能电站,采用三维动力有限元分析系统研究其上库面板坝的地震反应,主要包括坝体加速度、面板动力响应、接缝变位情况以及库底防渗土工膜的动应变等。计算结果表明:由于库底回填料的存在,坝体加速度放大效应被明显削弱;面板周边以受拉为主,中部大部分区域受压;垂直缝呈现出周边张开、中间闭合的趋势;土工膜的顺河向和坝轴向的动拉应变皆小于屈服应变,最大应变出现在库底材料分界处,为提高坝体渗透安全性,建议对主堆石区与连接板相接处的回填料进行适当范围换填的处理措施。研究成果可以为类似工程提供参考。

Dynamic Response Analysis of Concrete-faced Rockfill Dam on Deep Reservoir Bottom Backfill

The pumped-storage power station is widely used and can change the excess electric power at low grid load into high-value power during the peak period.Limited by the topography and geological conditions,the main dam of the reservoir of many pumped-storage power stations has to be built on reservoir bottom backfill.The existence of the reservoir bottom backfill in the concrete-faced rockfill dam will affect the modulus decay,damping ratio,and natural cycle of the dam,and is one of the important factors affecting the dynamic response of concrete-faced rockfill dams.In order to further study the influence of deep reservoir bottom backfill on the dynamic response of concrete-faced rockfill dams,by using a three-dimensional finite-element method and equivalent linear model based on a pumped-storage power station under construction,the seismic response of the upstream concrete-faced rockfill dam,including dam acceleration,dynamic response of the concrete panel,displacement of joints,and dynamic strain of the geomembranes,are studied and evaluated systematically.The results show that,because the existence of the reservoir bottom backfill material makes the dam body prolong the natural period of vibration,a high-order natural vibration period can easily coincide with the seismic predominant period and the high-mode vibration can be amplified,resulting in an acceleration distribution that is different from the standard distribution and an acceleration amplification that is weakened significantly.Surrounding areas of the concrete panel were in tension,most of the regional was pressed,the net tensile stress of the concrete in the panel was within the bearing capacity of the concrete,and the concrete panel is safe,but it is still necessary to take reasonable measures in corresponding parts in order to avoid the hazard due to potential cracks.Vertical joints were open around slabs and closed on the river valley.Vertical joints present a peripheral open-middle-close trend,and the results closer to the condition of no reservoir bottom backfill show that the effect of the joint deformation is small when built on either rock or rockfill.The dynamic strain of the geomembrane along and vertical to the river was less than the yield strain;the maximum strain appears on the boundary of the materials due to the obvious difference in material properties between the main rockfill zone and reservoir bottom backfill zone.We recommend that the replacement method used in an appropriate zone between the main rockfill zone and concrete plate can improve the dam safety of penetration.This paper can provide a reference for similar projects.