Analysis on the formation of the Moli landslide and river blockage risk in Guoye Town, Zhouqu County of Gansu Province

Due to the heavy rainfall, from February 26^th to 28^th 2021, the Moli landslide in Guoye Town, Zhouqu County, experienced creeping deformation with the development of slope cracks and obnious signs of deformation. A total of of 92 households with 402 people were affected, causing a direct economic loss of approximately 14.463 million yuan. This study focuses on the Moli landslide in Guoye Town, where the geological environment and physical and mechanical properties of the soil were deeply understood through remote sensing interpretation, aerial photography, and geological investigation. The cause of the landslide formation was analyzed in detail, and the stability of the landslide was calculated theoretically and analyzed for displacement monitoring. Based on field investigation and drilling analysis, the Massflow numerical model was used to simulate and predict the Moli landslide in Guoye Town, Zhouqu County. The range and thickness of the source area were determined to predict the accumulation process of the landslide and the risk of river blocking. The height of the river blocking and the harm caused by the landslide to the upstream and downstream regions were predicted. The results showed that: (1) Moli landslide is a super-large deep landslide with a long tongue shape, clear shape and deformation, and composed of broken phyllite and broken stone soil. The average depth of the slide body is 40m, and the total volume is 21.2 million stere. (2) The main factors of landslide formation are unfavorable topographic conditions, softening of rock and soil, strong tectonic movement, rainfall infiltration, and front river erosion. (3) The landslide has the risk of destroying the landslide houses, roads, and blocking the river. It is suggested that the residents threatened by the Moli landslide should take measures to avoid danger and relocate as soon as possible. This study can provide reference for the formation mechanism and emergency prevention and control of similar landslide geological disaster chains.