Dynamic analysis of the stabilized Wangjiayan landslide in the Wenchuan Ms 8.0 earthquake and aftershocks

Abstract

This paper discusses the effect of the May 12, 2008 Wenchuan earthquake on a landslide where stabilization work had taken place and compares the results to sites without stabilization. Contours of shear strain increment and displacement values obtained using a FLAC3D simulation show that the Wangjiayan landslide, which had stabilization work, was stable before the Wenchuan earthquake. Simulations using input strong motion accelerations from the main shock recorded at Qingping station, within the main seismic fault zone, suggest a shear strain increment about 3,000 times more than it was before the main shock. Although the stability of the stabilized landslide decreased during the earthquake, the displacement values were very small. Modeled displacements suggest that the piles played a major role in keeping the slope from sliding. The anti-slide piles were subjected to high shaking acceleration. The strong ground motion records for a time range of 10 to 30 s show that the piles generally experienced accelerations in the range from 0.0 to 3.0 g, with a few spikes of about 5.0 g. Special observation stations were set up to monitor the slope motion at Qingchuan town, 150 km far from the Wangjiayan landslide, along the main central seismic fault zone, after the Wenchuan earthquake. The variation in acceleration with time and the FOS versus time of the Wangjiayan landslide were investigated using these acceleration records of the aftershocks as input data. The aftershock accelerations did not decrease the stability of the Wangjiayan landslide, but an amplification effect on the acceleration of the slope at different elevations was illustrated.