SEISMIC DAMAGE ANALYSIS OF ROAD SLOPES IN WENCHUAN EARTHQUAKE

Seismic damages of road slopes in mountainous areas have different characteristics in mechanism and types from those in flain. Based on cases of damaged road slopes in the Wenchuan earthquake,failure mechanisms and types of the road slopes for cutting and embankment slope and slopes around bridge and tunnel,as well as retaining structures,are analyzed. Slopes stabilized by using anchored foundation beams or lateral loaded piles with prestressed anchors have better performance in the earthquake. The reason is that these structures make both structures and soils become integral,and so deformation between structures and soil is consistent. Geogrid or other reinforced embankment slopes have better performance in the earthquake;but the aseismic performance of embankments without reinforcement,particularly high embankments,is poor. Based on the cases of liquefaction or soft soil layer-induced settlement,it is suggested that engineers in aseismic design should pay attention to liquefaction-induced settlement at the toe of the slopes constructed on sandy soil layers and take measures to prevent from pavement failure caused by the settlement on soft soil layers and slope instability caused by the settlement at the toe of the slope. At tunnel portals and portal slopes,engineers should strengthen aseismic design of retaining structures. Safety and stabilization of bridge abutment,foundation and transition between abutment and embankment constructed on slopes are dependent of the slope stability;and so aseismic design of the slope, on which those structures are constructed,should be strengthened. For bridges constructed along the bank of river,unstable slope can damage the bridges,some measures in aseismic design should,therefore,be taken into consideration. At present,codes for aseismic design of roads and railway have few contents for how to design slope and retaining structures;and so the achievements obtained will be helpful to revision and supplementary of the codes.