Characteristics of Seismic Hazard in a V-Shaped Valley and Hazard Mitigation Methods

Abstract

The distribution of hazards triggered by strong earthquakes showed great differences with traditional experience that gained from normal condition or moderate earthquake. This paper researches the differences and discusses the effect on road in V-shaped valleys. The distribution map of slope failures triggered by Lushan earthquake along roads is worked out by detailed investigation. Abnormal areas of seismic hazards are found and marked in the map. Then, co-seismic hazards and post-seismic hazards are researched in detail along Yingxiu-Wolong section of S303 road. V-shaped valleys are abnormal areas in strong earthquakes, where the geological hazards can be extreme large. Rock avalanche is the major type of co-seismic hazard, and debris flow is prone to occur and is the most harmful post-seismic hazard. For new built roads, the line elevation is as high as it can be if the economy and technique are acceptable. In strong earthquake-stricken area, makeshift roads are adopted in damage trunk roads to ensure the traffic. Reconstruction of formal roads should not be started until the end of the active period. The line elevation with enough vertical clearance over the river should be adopted to prevent the post-seismic debris flow hazard.