THE INFLUENCE OF RAINFALL ON 6.24 XINMO LANDSLIDE

In the early morning of 24 June 2017,a landslide occurred in Xinmo village where located in the Wenchuan earthquake stricken zone raised great concerns in China and worldwide, because the landslide killed more than 80 people, damaged many houses, highways and facilities, and the volume is up to 8×106 m3. The preliminary research indicated that 1)historical earthquake seriously influenced the stability of the Xinmo landslide and generated several cracks near the ridge; 2)the slow-moving landslide cannot been detected in time due to tough geological condition and the limitation of observation equipment; and 3)a catastrophic landslide occurred without any prevention and mitigation measurements. Rainfall is main factor to trigger landslides except earthquake factor in the earthquake stricken zone. Furthermore, the Xinmo landslide was in a rainy weather in a rather long period before its occurrence. In this study, we aim to analyze the influence of rainfall on the Xinmo landslide by analyzing the rainfall characteristics in terms of yearly rainfall, monthly rainfall, daily rainfall and hourly rainfall. The rainfall data is obtained from the three rain-gage stations near the landslide. The results demonstrate that rainy weather in a long period before the landslide occurrence is the main reason to trigger the landslide totally failure. In particular, a rapid increased daily rainfall in April 9 accelerated the moving speed. To some extent, the landslide behaved some hysteresis on a larger daily rainfall in May 11 and June 14. In addition, a critical rainfall per hour and accumulative rainfall may be not adjusted to evaluate the slow-moving landslide. Accumulative effect of prolonged and low-intensity rainfall on slow-moving landslide cannot be neglect.