THE MECHANISM OF INITIATION AND MOTION OF THE RAPID AND LONG RUNOUT LANDSLIDES TRIGGERED BY THE 2008 WENCHUAN EARTHQUAKE

The 2008 Wenchuan earthquake triggered many rapid and long runout landslides, which made great loss of property and human lives directly. It is very important to understand the mechanism of initiation and motion of the rapid and long runout landslides. In this paper, field investigations on some typical landslides are introduced at first, and then the ring shear tests for simulating the initiation and motion of the Donghekou landslide are presented in details. The real seismic wave monitored in Shifang station was applied in the simulation test for the landslide initiation, while three different conditions of water content (dry, partially saturated, and fully saturated) were applied for the samples in the simulation tests to simulate landslide motion. It was found that the valley water and groundwater played a key role in the long runout and rapid landslide motion process during the great earthquake. This makes the difference for where landslide occurred but stopped soon and where landslides moved for long distance with high speed and killed many people. For the purpose of disaster mitigation, we strongly suggest that:(a) Avoid locating village in the landslide motion path, because the same event will occur in the future; (b) Avoid locating village and people on the landslide, because the landslide will deform easily with the seismic activity; (c) The attention should also be paid for landslide and debris flow during the reconstruction process for disaster mitigation in long period. Keywords: Wenchuan Earthquake, rapid and long runout landslides, ring shear tests, initiation, motion