On July 10

2013

a high-position landslide-debris flow was triggered by the heavy rainfall at Wulipo Sanxi village

Dujiangyan city

Sichuan province. The landslide-debris flow caused serious damages to Sanxi village. On the basis of further field investigation and previous research results

the formation mechanism and evolution process of the Wulipo landslide-debris flow are analyzed. Considering the actual mechanical behavior of the Wulipo landslide

the crack extending criterion under hydrostatic pressure and landslide start-up criterion under rainfall are calculated. The results show that the evolution process of the Wulipo landslide-debris flow includes following steps: formation of unloading crack

crack extending under hydrostatic pressure

slope sliding along the potential sliding surface under the effects of both hydrostatic and hydrodynamic pressures

rift trough forming

landslide reactivation due to heavy rain

rock blocks falling and accelerating

shoveling and moving along the valley

stacking and stop moving. By deducing minimum depth of water in the crack leading to crack automatically developing

critical water height in back crack and critical rainfall intensity causing slope instability

it is concluded that the crack could automatically develop when the depth of water in the crack reached 11.3 m; and the slope would lose its stability once the height of the water level in back crack reached 9.8 m.