The mechanisms and causes of the sudden failure of the Aznalcóllar tailings pond were investigated. The dam underwent displacements of up to 55 m along a 700 m length, releasing large quantities of acidic waters and 5.5 million m3 of pyrite and pyroclastic tailings. It was a progressive type of failure, allowed by the brittle response of the pre-consolidated and cemented Guadalquivir blue clays and the high pore pressures left from the incomplete consolidation of the dam’s foundation. Special modelling difficulties were posed by the need to incorporate the strain softening behaviour of the clays. The results show that although the timing of the failure could have been approximated using equivalent ductile properties, predicting the shallow, planar geometry of the failure surface observed would have required a precise representation of the brittle response. The failure triggered liquefaction of the tailings, which accelerated at more than 0.1 g. This transition was modelled by migrating from a coupled effective stress approach employing implicit integration to a total stress formulation using an explicit solver.

中文翻译：

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Aznalcóllar（西班牙）尾矿坝故障的解释

研究了 Aznalcóllar 尾矿池突然失效的机制和原因。大坝沿 700 m 长位移了 55 m，释放了大量酸性水和 550 万立方米的黄铁矿和火山碎屑尾矿。这是一种渐进的破坏类型，这是由于预固结和胶结的 Guadalquivir 蓝色粘土的脆性响应以及大坝地基不完全固结所留下的高孔隙压力造成的。由于需要结合粘土的应变软化行为，造成了特殊的建模困难。结果表明，虽然可以使用等效延性属性来估计失效的时间，但可以预测浅层、观察到的破坏表面的平面几何形状需要精确表示脆性响应。失败引发尾矿液化，液化速度超过 0.1 克。这种转变是通过从使用隐式积分的耦合有效应力方法迁移到使用显式求解器的总应力公式来建模的。