As results of engineering activities,such as excavation at slope toe,surcharge loading onto slope surface, improper irrigation of sloping farmland,etc.,loess landslides are occurring frequently in Western China,posing a great threats to the safety of life and property of local residents.Taking Shajingyi Landslide of Lanzhou City as case study,this research conducted field geological surveys for investigation on the main characteristics of loess landslide and its triggering factors.Then confining depressure triaxial tests were implemented to interpret deformation and failure of loess slope during excavation.Based on FLAC3D,the excavation process of loess slope was examined by numerical simulation,and soil stresses and deformation at different depths were collected for analysis in order to re-veal mechanism of slope stability or failure during excavation.Research results suggested that Shajingyi Landslide was derived from a unreasonable excavation at slope toe,resulting in a resurgence of an old underlying landslide, typical of retrogressive landslide; During the excavation process,stress redistribution took place in the slope body with stress state regulating simultaneously,and the slope deformation gradually increased with excavation progress;Ensuing the excavation,there were large amounts of shear fractures generated on the middle open surface of the slope as well as tension cracks developed on the back edge,undermining slope stability,and soon it come to fail af-ter a larger deformation in the upper part of the slope was observed.%坡脚开挖、坡面堆载、不合理灌溉等人类活动诱发的工程性黄土滑坡灾害频频发生,对于当地居民的生命财产安全构成极大威胁.本文以兰州市沙井驿滑坡为研究对象,在工程地质勘测的基础上,研究滑坡的基本特征及导致滑坡发生的关键因素.通过减围压三轴试验研究黄土边坡开挖过程中土体的变形破坏特征.基于FLAC3D数值模拟方法,对黄土边坡的开挖过程进行模拟,分析开挖过程中边坡不同深度的土体应力及变形发展规律,揭示开挖过程中坡体稳定性变化规律及滑坡启动机理.结果表明,沙井驿滑坡是由于坡脚不合理开挖导致老滑坡复活,为牵引式滑坡;在开挖过程中,坡体内发生应力重分布,应力状态不断发生变化,随着开挖的进行,坡体变形逐渐增大;开挖结束后,坡体中部产生大量剪切裂缝,后缘产生张拉裂缝,坡体稳定性降至最低,中上部均有较大变形,最后发生失稳.
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