Abstract
During the 2008 Sichuan earthquake (M8.0), more than 60, 000 landslides were triggered and 800 landslide dams formed. Those dams with high risk of collapse threatened the rescue activities, and almost all the large ones were treated by digging sluiceway immediately after the quake. Although the risk of collapse of the landslide dams was moved, not all of the countermeasures were based on ideal methods. To analyze the formation of landslide dams and then perform reliable countermeasures, we investigated some of them, and here a landslide dam occurring on Tianchi area is described. The grain size analysis revealed that the displaced landslide materials experienced fragmentation and segregation during the movement with long travel distance. The S-wave velocity profile of the dam revealed that the dam site has higher S-wave velocity, compared to those landside dams that had suffered collapse failure during the construction of drainage work, showing that the structure of the dam is consisting of densely deposited materials. This kind of dam body has lower permeability capable of retarding the seepage force to trigger collapse failure of the dam body due to piping. Big blocks on the surface will also enable the dam body to have stronger resistance to overflow and then to avoid the possible collapse failure immediately after the occurrence of overtopping.
