Pore-water pressure accumulation during closely spaced earthquakes: Fundão Tailings Dam

Pub Date : 2022-11-25 DOI:10.1080/25726838.2022.2147682

T. Stark, Jiale Lin, E. Gimenes

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Abstract

ABSTRACT This paper focuses on pore-water pressure accumulation in loose sandy tailings during three (3) earthquakes within four minutes and the accompanying decrease in effective stress to assess the dynamic stability of the Fundão Tailings Dam, which failed on 5 November 2015. Results of laboratory cyclic direct simple shear tests are used to illustrate the accumulation of pore-water pressures with closely spaced low-level cyclic events. The seismically-induced pore-water pressures in the loose sands below the left abutment downstream slope and setback area are used to estimate the decrease in factor of safety with time until failure occurred within 20–30 minutes of the earthquakes. Field cone penetration and standard penetration test conducted prior to the failure are used to calculate the factor of safety against liquefaction to estimate pore-water pressures generated during the fore, main, and aftershocks in the sandy tailings. The effective stress stability analyses utilise a liquefied shear strength ratio for the sand tailings below the left abutment downstream slope and toe of the plateau because the sand tailings reached the critical state condition due to a reduction in the effective stress. SITE LOCATION: 20.206500°S, 43.467111°W

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近距离地震期间的孔隙水压力积累：Fundão尾矿坝

摘要针对2015年11月5日垮塌的fund尾矿坝，研究了4分钟内3次地震作用下松散砂质尾矿的孔隙水压力累积及有效应力减小情况。使用实验室循环直接单剪试验的结果来说明孔隙水压力与紧密间隔的低水平循环事件的积累。利用左桥台下游坡面及后退区下方松散砂土的地震诱发孔隙水压力，估算了地震发生后20 ~ 30分钟内安全系数随时间的衰减。利用破坏前进行的现场锥贯入和标准贯入试验，计算了砂质尾矿在前、主、余震过程中产生的孔隙水压力的抗液化安全系数。有效应力稳定性分析采用液化抗剪强度比对左桥台下游坡脚及高原脚尖以下尾砂进行分析，因为尾砂由于有效应力的降低而达到临界状态。站点位置:20.206500°s, 43.467111°w

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