兰州市安宁区凤凰山上洼子滑坡形成条件及稳定性分析

Analysis of the features and stability of Shangwazi landslide in Phoneix mountain of Anning District,Lanzhou City

兰州市安宁区凤凰山上洼子滑坡是近期首次发生在新生界新近系和第四系地层且在人类工程活动下直接诱发的特大型滑坡.在野外调查勘察、钻孔及室内土力学试验的基础上,对上洼子滑坡的形成条件及稳定性进行分析计算,结果表明,上洼子滑坡体是一处典型的黄土泥岩切层滑坡,属推移式牵引混合滑坡;上洼子滑坡体在天然状况下处于基本稳定状态;在暴雨状况下处于欠稳定基本稳定状态;在地震加速度为0.2 g时处于不稳定状态,易发生失稳下滑.通过对滑坡发生条件的研究,以期对西部其他此类地层条件下的工程活动,特别是北环路建设过程中其他地段的开挖及灾害治理提供借鉴.

Shangwazi landslide, located in the Phoenix mountain of Anning District, Lanzhou proper, is regarded as a huge landslide recently formed in the Cenozoic Neogene strata and the Quaternary strata, and it was directly induced by human engineering activities. On the basis of field investigation, drilling and soil mechanics experiment, its formation conditions and the stability were analyzed and calculated. The results showed that the Shangwazi landslide is a typical loess-mudstone cutting layer landslide belonging to both thrust load-induced and retrogressive landslide. Under natural conditions the landslide is in a stable state, but it will become unstable or barely stable under rainfall condition. What is more, a seismic acceleration of 0.2 g will cause the landslide in to be unstable. The study of the landslide formation conditions and development mechanism is expected to provide reference for other western regions under similar geological conditions caused by engineering activities, especially for the north ring road construction in Lanzhou during its process of excavation and disaster management.