Study On Classifications And Mechanisms Of Collapse Disaster On Highway Slope After Wenchuan Earthquake

A devastating earthquake of magnitude 8.0 was happened in May 12,2008, Wenchuan, China. This earthquake induced large numbers of geology disasters along highways and damaged many infrastructures. Large numbers of rock falls were happened everywhere which added huge troubles to the evacuation and rescue of people after quake. According to the survey conducted recently, many high steep slope failures not only induced rock fall which damaged the highway facilities, the quake also produced several cracks and loss of rock mass, a technical term "cracked rock mass" is introduced. Those induced cracks develop and increase as the rainfall, gravity and subsequent small earthquake happens. In this situation, potential geology disaster will happen which poses great safety issues to the reconstruction and running of highways after the earthquake.This study is based on a widely literature of the previous published results. A particular area near highway 303 was selected where extensively geology data were incorporated. A series of geology disaster surveys were done on this portion of high way, different geology hazards were sorted and categorized in different groups. The rules of earthquake induced rock fall were developed and a theoretical mechanism about how these geology disasters happened were established and well studied. To sum up, this study has achieved the following results.(1) A brief introduction about how these geology disaster happened along the section of K0+000—K45+500, Highway S303 was given in the beginning. After a thorough investigation of all the disasters happened along the highway s303, the numbers and properties of these disasters were summarized, according to the current stress strain conditions, different rock fall disasters are sorted into:roughly stable, unstable during quake, post quake stable, and post quake unstable, respectively.(2) About 99 rock fall disasters were comprehensively studied and 115 cross sections were drawn in this study, the inclination, height of the slope, dip, shape, structure and rock properties were achieved.(3) The study is focused on the rock fall, what it affects, how it happens, when and where it will happen, what's the relationship between rock fall source and road shoulders were all intensively studied. Based on these study areas, rock falls happened after quake were sorted and categorized in different groups. These categories act as a standing out part in sorting post earthquake geology disasters.(4) Based on the comprehensive study of the geology disasters after earthquake, a series of mechanisms about how rock falls happened were concluded, namely they are:quake induced tension cracks-sliding, quake induced tension cracks-tilting, quake induced tension cracks-failure-staging respectively.