Collapsing Mechanism of Rock Slopes in Wenchuan Earthquake

To study the collapsing mechanism of rock slope under the influence of earthquake, a field investigation on damages of rock slopes located in Wenchuan seismic area along Guanghan- Yuejiashan railway was particularly presented. It was found that the collapsing mechanism was characterized by throwing of rock blocks collapsed under seismic effects, which is different from the case under the traditional sliding hypothesis. Finite-difference dynamic numerical method was applied to evaluate the stability of wedged rock mass. The calculated results showed that vertical peak ground acceleration (PGA) at top of rock block was 0.9 times as large as that of horizontal peak ground acceleration, and PGA in rock block was about 1 time larger than that of intact rock mass. Rock block was downwards thrown out with an included angle of about 41.6° under strong earthquake instead of horizontal movement. The preliminary investigation on collapsing mechanism of rock slope under earthquake was discussed, and it is needed to do further research on seismic response of rock mass.