Research On The Mechanism And The Kinetic Characteristic Of Donghekou Landslide

8.0-Magnitutude earthquake occurred on 14:28,May 12th,2008,in Wenchuan,Aba county,Sichuan Province.It triggered a landslide on the mountain near the Donghekou, Hongguang Village Qingchuan County,Guangyuan City.The landslide damaged four villages and the Donghekou power station and two buses which were on the way to the Qingchuan County,780 were killed during this disaster.The large landslide war trigged by the wenchuan earthquake, was characterized by typical kinetics, such as ejected movement with considerable velocity, runout distance of debris flow and so on. So, the analysis of the type of the landslide is very necessary and important to afford theoretical and practical significance, which include their characteristics, failure process and mechanism.The paper focuses on the Donghekou landslide in Qingchuan, Guangyuan City, Sichuan province. According to a large number of geological field investigation and monitoring, geotechnical test, and collecting and summarizing a various of the information of earthquake, the characteristics, mechanism and kinetics of the landslide were systemically analyzed. On the other side, internal factors (such as, the geological setting, topographic and geomorphological features and rock mass structures) and external factors (such as, compound effect of horizontal and vertical acceleration, shock amplification with elevation, the role of time form seismic shock) were investigated for analyzing how impact on the landslide instability. Then, the momentum transfer and anti-push approach were used to calculate the velocity of the landslide respectively.The result of the study showed that the wenchuan earthquake is direct triggering factor for the Donghekou landslide. While the occurrence of the landslide also is relate to the lithology, geological structure and rock mass structure in the study area. Under the impact of role of time form seismic shock, the cracks firstly occurred on the top of slope, and gradually perpendicular developed down upon the bottom of the layers; at the same time, the cracks developed to extended horizontal direction with the development of vertical cracks, finally the slipping surface were formatted. The cracks on the both sidewalls of the landslide were enlarged very fast. The greatly destructed rock mass by cutting from a series of discontinuous surface was ejected by seismic shock. Due to the high position energy of the ejection, the landslide collapsed and hit the ground, and translated into a debris flow with high speed and traveled about 2 km before stopped. By the momentum delivering method and reversing computing method ,the author has calculated out that the most dropping speed was 59.9m/s,the lasting moving time was 63 seconds,and the average speed was about 36m/s.