开挖致使古滑坡复活变形机理研究
Reactivation and deformation mechanism of ancient landslides by excavation
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摘要: 以三峡库区兴山县大礼溪村古滑坡为例,通过地质勘察、近1 a的现场宏观巡查、人工GPS位移监测数据、自动GPS监测数据等,在剖析该滑坡存在的古滑坡特征的基础上,分析了滑坡复活过程中地表裂缝发育的时空规律以及变形特征,并结合Geo-Studio模拟确定了开挖和降雨两种作用对古滑坡复活变形的影响及主次关系。研究表明:①大礼溪滑坡为地质历史时期形成的含软层中—陡倾顺层岩质古滑坡;②滑坡复活变形与开挖作用密切相关,前期集中于临近最早开挖区域的前缘Q3附近,并沿着开挖方向逐渐在前缘Q4、Q5出现,最终在前缘Q5附近演化出次级滑坡,与此同时,纵向上变形逐渐向中后部推进,表现出渐进后退的发育特征;③开挖作用是滑坡变形复活的主要因素和诱发因素,降雨为激发因素,两者共同作用促使变形持续发展。Abstract: The Dalixi ancient landslide in Xingshan County in the Three Gorges Reservoir area is taken as an example. Based on the analysis of its characteristics, the deformation characteristics and temporal-spatial laws of surface cracks of the ancient landside in the process of landslide revival are analyzed by use of geological survey, site inspection for nearly one year, artificial GPS displacement monitoring data and automatic monitoring data. Based on the Geo-Studio simulation, the influences of excavation and rainfall on the revival deformation of the ancient landslide and the primary and secondary relationships are determined. The results show that: (1) The Dalixi landslide is a middle-steep consequent ancient rock landslide with soft layer in geological history period. (2) The deformation of Dalixi landslide is closely related to excavation. In the early stage, it concentrates near the leading edge Q3 of the first excavation area, and gradually appears along the excavation direction at the leading edge Q4 and Q5, and finally evolves into the secondary landslides near the leading edge Q5. At the same time, the vertical deformation gradually advances to the middle and rear, showing the characteristics of progressive retrogression. (3) The excavation is the inducing factor for the revival of landslide deformation, and the rainfall is the stimulating factor. Both of them work together to promote the sustainable development of landslide deformation