基于时程分析法的尾矿坝动力稳定性研究

Study of the dynamic stability of tailings dam based on time-history analysis method

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,为对其扩容前后坝体动力反应和稳定性进行系统研究和合理评估.采用动三轴试验,对库内3种尾矿(尾细砂、尾粉砂和尾粉土)的动强度和动模量与阻尼比进行了测试;综合运用时程分析法、剪应力对比法、有限元极限平衡法和软化模量法,对扩容前后尾矿坝的液化范围、安全系数和坝顶震陷等进行了定量分析,并对常规极限平衡法的局限性和适用条件进行了探讨.研究结果表明:1)尾矿的动剪应力比随围压的增大而有所降低,破坏时动孔隙水压力比随着破坏振次的增加而增大;2)在设置有效的排渗措施的情况下,尾矿坝的液化区域主要位于尾水覆盖区域表层;3)永久变形表现为坝坡上部沉降、下部向下游方向挤出的形式,且加高后坝顶震陷量和震陷率均有所增大.扩容后大沙河尾矿库坝体的动力稳定性有所降低,但仍能满足相关安全控制标准的要求.

The dynamic response and slope stability of Dashahe tailings dam in southern China during earthquake was studied for the scenarios before and after dam raise.Dynamic triaxial tests were carried out to obtain the dynamic shear strength,shear modulus,and damp ratio of three different tailings samples,namely,fine sand,silty sand,and silt.Numerical analyses were then conducted to determine the extent of liquefaction zone,factor of safety of the dam,and subsidence of the dam crest,using time-history analysis,shear stress contrast,finite element limit equilibrium,and softening modulus method.In addition,the limitations of conven-tional limit equilibrium methods were discussed.The results show:1)dynamic shear stress ratio of the tailings decreases with the increase of confining pressure due to dam raise,and dynamic pore water pressure ratio at failure increases with the increase of loading cycles;2)Liquefaction mainly occurs at shallow depth underneath tailings pond both before and after dam raise,provided effective drainage system is in-place;3)Permanent deformation takes place in the form of subsidence in upper part of the dam and toe extrusion at the lower part.The subsidence of the dam crest increases with the dam raise.Nevertheless,the Dashahe tailings dam still meets Chinese tailings dam safety standards under design earthquake load.