GEOLOGICAL HAZARDS DUE TO WENCHUAN EARTHQUAKE ALONG YINGXIU TO WOLONG HIGHWAY

The highway from Yingxiu town to Wolong town is the nearest highway to the epicenter of Wenchuan Earthquake. The geohazards long and damage to the highway are the most serious. This paper presents a comprehensive investigation of the geological hazards due to the earthquake along the highway.Based on their characteristics,the geohazards are divided into four types.They are instability of highly weathered rockmass and soil on the upper part of the slopes,instability of rock mass cut by geological structural surface,landslides and debris flows. It analyzes the developmental law of geohazards along the highway. The geohazards show significant deviations between the two sides of the back range faults at the Longmen Mountain fault zone. The reasons are the seismic isolation effect of the deep fracture,scaling effect of the landforms,and geologic structures. The slope steepness and position of seismic instabilities have been studied via the analysis of 134 geological sections. The results show that the slope steepness of seismic instabilities are distributed within the range of from 33 to 84,mainly from 40 to 65. So,it can be concluded that the geohazards caused by the earthquake mainly took place on the road slopes steeper than 40. The failure zones caused by seismic force mainly distributed on the upside of the road slopes. The instability positions are mainly upon the parts with slope gradients more than 040.For the study of slope dynamic instability,four geologic structure models are put forward.They are rocksoil and strong weathered rock slopes,rock slopes with outward inclined structural plane,massive structure rock slopes and crushedrock soil slopes. It analyzes the type and characteristics of eachof the four geologic structure models. 