Effects of vertical seismic force on initiation of the Daguangbao landslide induced by the 2008 Wenchuan earthquake

Abstract

This paper analyses the effects of vertical seismic force on initiation mechanism of near-fault large-scale landslides by using the Daguangbao landslide induced by the 2008 Wenchuan earthquake as an example. Field investigations showed that tension failure plays an important role in failure mechanism, and the tension failure is due to the effect of a large vertical seismic motion that occurred in the meizoseismal area during the earthquake. Firstly, two key issues in seismic analysis of near-fault large-scale landslide are proposed: i) how to select and correct the severe near-fault excitations with significant co-seismic displacements and ii) how to consider the effect of the landslide scale on estimation of material strength. Then, in order to investigate the effect of the severe vertical seismic force on the initiation of the huge Daguangbao landslide, five cases, 1) static; 2) pseudo-static only-horizontal; 3) pseudo-static horizontal-and-vertical; 4) dynamic only-horizontal; 5) dynamic horizontal-and-vertical, are performed using the finite difference program FLAC3D. The simulation results are presented in terms of tension failure area, factor of safety, and displacement. The results confirm the significant effects of vertical seismic force on seismic slope failure mechanism as the tension failure areas and the displacements observed in the case of horizontal-and-vertical are larger than those observed in the case of only-horizontal.