Formation Mechanisms of High Rock-slope Deformation Under Heavy Rainfall
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摘要: 东南亚某在建水电站坝址右岸边坡在开挖过程中，不同高程部位产生了一系列的变形破坏现象，主要表现为裂缝、局部滑塌及滑移，已处于临界失稳状态。基于边坡开挖后的实际工程地质条件、现场地质调查及监测成果，总结了该边坡的变形特征，系统分析了变形破坏现象的成因机制。研究结果表明：边坡开挖后形成临空面，应力场重新分布调整，岩体向临空面回弹，加剧了岩体裂隙的张开度以及贯通程度，为雨水入渗提供了良好的通道，使得F11断层中物质吸水软化，产生不均匀变形，致使裂缝以及局部滑塌出现；后期2次强降雨，加速裂隙向深部延伸发展，迅速软化岩（土）体，压缩蠕变累计量大，滑面贯穿形成蠕滑–拉裂型滑坡。研究为边坡后续开挖及支护提供一定的参考。Abstract: A series of deformation and failure occurred at different elevations during the excavation process on the right bank slope of a dam site of a hydropower station under construction in Southeast Asia, which were mainly manifested as cracks, partial collapses, and landslides, and the slope was in a critical state of instability. Based on the actual engineering geological conditions, field geological survey and monitoring data after the excavation of the slope, the deformation characteristics of the slope were summarized and the cause mechanism of the deformation and failure was analyzed. The results show that the free surface is formed and the stress field is redistributed after slope excavation, and the rock mass rebound to the free surface, which intensifies the opening and penetration of the rock mass fissures, and provides a good channel for rainwater infiltration. The material in the F11 fault absorbs water and softens, resulting in uneven deformation, which lead to the cracks and partial landslides. The fracture accelerated its development to the deep and the rock (soil) softens rapidly as well as accumulates a large amount of compression creep due to the twice of heavy rains, the creep slip-pull crack type landslide is formed after the slip surface penetrates. This research could provide a certain degree of excavation and support for the later period.
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