考虑弱化效应的加高扩容尾矿坝地震可靠度分析及风险评价

Seismic Reliability Analysis and Risk Assessment of an Expanded Tailings Dam Considering Seismic Weakening Effect

地震荷载下的坝体稳定性及溃坝风险始终是岩土工程界的研究重点之一。引入弱化系数考虑地震对尾矿坝筑坝材料的弱化效应,采用极限平衡拟静力法与光滑粒子流体动力学方法结合进行尾矿坝地震可靠度分析及风险评价。利用极限平衡拟静力法与蒙特卡罗方法寻求可能的失效样本,进而采用自主研发的SPH(smoothed particle hydrodynamics)程序模拟失效样本下尾矿坝失稳过程以及最终堆积状态,引入临界位移值确定滑动面积以评估尾矿坝的失效后果。应用本文方法对云南省斑毛沟加高扩容尾矿坝的稳定性及风险进行了评价,算例分析表明:随尾矿坝扩容高度的上升,旧坝的稳定性基本保持不变,而新坝的稳定性持续降低,扩容高度完成后,尾矿坝最小安全系数与规范要求值接近,需要重点关注其稳定性。可靠度分析结果表明:当尾矿坝筑坝材料变异系数为0.1时,其相应的失效概率为1%,该失效概率值的变异系数约为0.3。不考虑地震作用对筑坝材料的弱化效应,扩容尾矿坝的失稳风险为309.17 m^(2),考虑弱化效应后,随弱化系数减小,扩容尾矿坝的失稳风险增大。随着弱化系数的减小,临界位移值对失稳风险的影响逐渐减弱,弱化系数大于0.5时,临界位移值对扩容尾矿坝的失稳风险影响显著。

The stability of dam and risk of dam failure under seismic load are always one of the research focuses in geotechnical engineering.The limit equilibrium pseudo-static method and smoothed particle hydrodynamics(SPH)method were combined to perform seismic reliability analysis and risk assessment of tailings dam by introducing weakening factor to account for the weakening effect of soil properties due to earthquake actions.The limit equilibrium pseudo-static method and Monte Carlo method were used to find possible failure samples,which were subsequently transferred to the self-developed SPH(smoothed particle hydrodynamics)program to simulate the instability process and to obtain the final depositions of the failed tailings dam.The sliding area of the failed tailings dam was determined based on the specified critical displacement value and was adopted to quantify the consequence of failed tailings dam.The method presented was used to evaluate the stability and to quantify the risk of an expanded tailings dam in Yunnan Province.The calculation results have demonstrated that the stability level of the old dam remains almost unchanged,whereas the stability of the new constructed dam deteriorates as the expansion work progresses.The minimum safety factor of the final expanded tailings dam approaches to the value documented in the code implying the necessity of conducting reliability analysis.The failure probability of final expanded tailings dam is determined to be 1%with a coefficient of variation of 0.3 when the coefficients of variation of soil properties are all assumed to be 0.1.Without considering the seismic weakening effect,the risk of the final expanded tailings dam is 309.17 m^(2) and it rises as the weakening factor decreases.The effect of critical displacement value on the calculated risk of final expanded tailings dam diminishes as the weakening factor decreases.When the weakening factor is greater than 0.5,the critical displacement value has a significant influence on the calculated risk of the expanded tailings dam.