Formation and failure mechanism of the landslide: a case study for Huaipa, Western Henan, China

A large landslide occurred on May 2, 2014, on the south bank of the Yellow River in Huaipa village, Mianchi County, Henan Province, China. The total volume of the slide was about 4 million m3. The landslide caused serious damage to the water-conveying pipeline at the foot of the slope, which was for water supply from the Yellow River to Manchi County and Yima City. After the event, the engineering geological characteristics, influencing factors and failure mechanism were investigated by field investigation and geological mapping. Then, the failure process and the effect of anti-tipping locked segment were presented by three-dimensional (3D) numerical simulation. The results showed that the destruction of the anti-tipping locked segment in the front edge due to open-pit mining was the main factor of slope failure. The sliding mass, composed of loose silty clay and heavily weathered sandstone and mudstone, and rainfall infiltration were other factors triggering the slide. According to 3D numerical simulation, the stability coefficient of the landslide was 1.35 in natural condition and 1.26 when the sliding body was saturated by continuous rainfall, before the anti-tipping locked segment was destroyed, while the stability coefficient decreased significantly to 1.04 after the anti-tipping strata were destroyed. The whole failure occurred when the sliding mass was saturated by continuous rainfall (the stability coefficient is 0.88). This paper can provide an insight into the effect of anti-tipping locked segment on the failure mechanism of landslide associated with open-pit mining and rainfall.