CENTRIFUGE MODEL TEST OF REACTIVATION MECHANISM OF JIANGDINGYA ANCIENT LANDSLIDE IN GANSU PROVINCE

The Jiangdingya ancient landslide is a huge scale landslide located in the Bailong River fault zone,in Zhouqu County,Gansu Province. Affected by fault activities,rainfall,river erosion,and human engineering activities,it has repeatedly revived and blocked the Bailong River,causing great disasters. In order to study the resurrection mechanism of Jiangdingya ancient landslide,based on the field geological survey,we focus on the centrifuge model test under the conditions of 10%,15% and 20% water content. The test shows that when the water content is 10%,only a few cracks are generated in the middle and rear part of the slope,but the landslide is still in a stable state as a whole. In the case of 15% and 20% water content,the landslide body is damaged. When the water content is 15% and 20%,the centrifugal acceleration required for the slope instability is 100g and 50g respectively. The test analysis shows that the Jiangdingya ancient landslide is a thrust-type landslide. Its deformation starts from the middle and rear part of the slope,where cracks are generated. Then the cracks gradually expand to the front edge and finally penetrate and cause the landslide damage. The deformation process of the landslide body is mainly divided into three stages: ①deformation initiation stage(crack formation stage); ②deformation acceleration stage(crack acceleration development stage); ③instability stage. The centrifugal simulation test and field investigation and analysis show that the factors for the resurrection of the Jiangdingya ancient landslide are mainly affected by rainfall and pore water pressure. It is a coupling sliding caused by the erosion of the front river and the movement of the middle and rear parts of the landslide caused by rainfall.