尾矿库加高扩容坝体动力反应与抗震性能分析

Analysis of dynamic response and seismic behavior of tailings dam for heightening and expansion

地震是引起尾矿坝事故的主要原因之一,对尾矿坝抗震性能的准确评估对于预防尾矿坝震害具有重要意义。尾矿坝的抗震性能包括液化可能性、动力稳定性和永久变形3个方面。以云南省狮子山铜矿的大沙河尾矿库加高扩容工程为背景,基于有限元时程分析法,对该尾矿坝在现状条件下、直接加高后和加高中增设排渗措施3种条件下的动力反应和抗震性能进行了计算和分析。结果表明,浸润线对尾矿坝的抗震性能有至关重要的影响。尾矿库加高扩容后,浸润线有明显抬升,在地震作用下会导致下游坡面发生液化,产生较大的永久变形,安全系数降低至规范值以下;采取增设坝体排渗设施后,有效地降低浸润线的埋深,能显著提升坝体抗震性能,使其满足相应抗震设防要求。另外,地震作用下尾矿坝的加速度放大系数相对较小,与坝高并非呈单调关系,这些特点与土石坝有差别。采用滑动位移分析法、等效节点力法和简化弹塑性分析法对尾矿坝的永久变形进行了计算,尽管具体量值和表现形式有明显差别,但均表现出永久变形随总坝高增高而增大、随浸润线降低而减小的趋势。

Earthquake is one of the main causes of tailings dam accident. It is very important to evaluate the seismic behavior of tailings dam in order to prevent earthquake damage of tailings dam. The seismic performance of the tailings dam includes three aspects：liquefaction possibility,dynamic stability and permanent deformation. Based on the finite element time-history analysis method,the dynamic response and seismic behavior of the Dashahe tailings dam in Yunnan Province,which is need to be heightened and expanded,were calculated and analyzed on the conditions of current state,heightening directly and heightening with additional drainage facilities. The results show that the phreatic line has an important influence on the seismic behavior of the tailings dam. When the tailings dam is directly heightened,the phreatic line is obviously uplifted,resulting in that some tailings of the downstream slope are liquefied,a large permanent deformation occurs and the safety factor is reduced to below the standard value. Additional seepage facilities can increase the depth of the phreatic line effectively and improve the seismic behavior of the dam significantly,so as to meet the corresponding seismic fortification requirements. The acceleration amplification factor of tailings dam under earthquake is relatively small and not monotonous with the dam height,which is different with earth-rock dam. The permanent deformation of the tailings dam was calculated by using the sliding displacement analysis method,the equivalent nodal force method and the simplified elastoplastic analysis method respectively. The results of the three methods have obvious differences in their specific values and forms of expression. But a tendency was showed by all three methods that the permanent deformation increased with the dam heightening and decreased with the phreatic line dropping.