On the initiation mechanism of the Daguangbao landslide triggered by the 2008 Wenchuan (Ms 7.9) earthquake

The Daguangbao landslide, with a volume of 1.16 × 109 m3 and an area of 7.2 km2, is the largest landslide triggered by the 2008 Wenchuan earthquake in China. To examine the initiation mechanism of this landslide, a detailed field investigation and a series of saturated triaxial tests were carried out. The field investigation revealed that the Daguangbao landslide initiated along a mylonite zone, the soil of which was mainly sand. Abundant groundwater was observed in the tunnel and the mylonite zone soils had high water contents. In addition, the experimental results showed that the soils from the mylonite zone have a high liquefaction potential. The pore water pressures in the soils under cyclic triaxial tests increased rapidly, which could have caused the soils failure. Therefore, the mechanism by which pore water pressure within the mylonite zone accumulates under seismic loading, which promotes a continuous decrease in the shear strength of soils, ultimately led to the rapid initiation of the Daguangbao landslide. •The DGB landslide initiated along a mylonite zone, the soil of which was mainly sand. The soils had high water contents.•The soils have a high liquefaction potential and that liquefaction can be triggered under VCP tests.•The increase in pore water pressure during the cyclic triaxial tests is affected by grain movement and crushing.•The pore water pressure increases under seismic loading. Ultimately, rapid shear failure of the DGB landslide occurred.