Rainfall is a common factor that triggers the instability of Victorian Brown Coal (VBC) open pits which facilitate some of the largest brown coal mining operations. There has been no relevant study on rainfall-induced slope instability of VBC open pits in literature. In this paper, a three-dimensional (3D) two-phase (fluid-solid) coupled finite element method (FEM) was employed to investigate the stability of Maddingley Brown Coal (MBC) eastern batter under different rainfall conditions. It was found that the batter tends to lead a circular failure path during large rainfall. With the increase in either precipitation period or rainfall intensity, the deformation, excess pore pressure and active pressure increased, while the matric suction decreased. The hydrostatic force in the confined aquifer underlying the brown coal seam increased during rainfall; meanwhile, the resisting force decreased. As a result, the shear strength decreased and thereby the stability of the batter decreased. The safety factor and the critical failure path of the eastern batter simulated in this study were consistent with the previous study on the Northern batter. This study is a strong supplement to the literature on rainfall-induced instability of VBC batters. In the meantime, it is significant to provide a reference to the application of sophisticated 3D numerical modelling for studying slope instability of brown coal and similar mineral deposits.

降雨是引发维多利亚褐煤（VBC）露天矿场不稳定的常见因素，这有利于一些最大的褐煤开采作业。文献中尚未有降雨引起的VBC露天矿边坡失稳的相关研究。本文采用三维（3D）两相流固耦合有限元方法（FEM）研究了Maddingley Brown Coal（MBC）东部面糊在不同降雨条件下的稳定性。发现在大降雨期间，面糊趋向于导致圆形破坏路径。随着降水周期或降水强度的增加，形变，过大孔隙压力和活动压力增加，而基质吸力下降。在降雨过程中，褐煤层下面的承压含水层中的静水压力增加了。同时，阻力减小。结果，剪切强度降低，从而面糊的稳定性降低。在本研究中模拟的东部击球手的安全系数和临界破坏路径与先前对北部击球手的研究一致。这项研究是对降雨引起的VBC面糊不稳定性文献的有力补充。同时，重要的是为研究褐煤和类似矿床的边坡失稳提供先进的3D数值模型的参考。在本研究中模拟的东部击球手的安全系数和临界破坏路径与先前对北部击球手的研究一致。这项研究是对降雨引起的VBC面糊不稳定性文献的有力补充。同时，重要的是为研究褐煤和类似矿床的边坡失稳提供先进的3D数值模型的参考。在本研究中模拟的东部击球手的安全系数和临界破坏路径与先前对北部击球手的研究一致。这项研究是对降雨引起的VBC面糊不稳定性文献的有力补充。同时，重要的是为研究褐煤和类似矿床的边坡失稳提供先进的3D数值模型的参考。