Rainfall deformation characteristics and influencing factors for a large deep level landslide in tuff grounds in Zhejiang, China

Although there have been a lot of studies on landslides in geologic hazards in China, the study on tuff landslides in southeast coastal areas is relatively lack. In view of this, based on the landslide of Xiageliao Mountain in Jinshui Village, Zhenbu Township, Qingtian County, by using automatic monitoring technology and analyzing the monitoring data of landslide deformation and rainfall, the deformation law and influencing factors of tuff landslide are discussed, which provides a basis for landslide stability analysis and landslide geologic hazards warning. The results show that: (1) tuff belongs to volcanic ash composition, with physical properties such as unstable mineral composition, high porosity and permeability, and easy fracture of thin layers, resulting in its strength and stability varying with water content. (2) The sliding deformation is mainly concentrated in the parts below the "primary and secondary platforms" (Zone I); The deformation of parts above "Level 1 and Level 2 platforms" (Zone II) is relatively small; There is basically no deformation in the trailing edge crack area (Zone III). (3) The overall annual movement speed of Xiageliao landslide is 10-15 cm/a. Affected by continuous rainfall or heavy rainstorm, the deformation curves of division I and II show a stepped evolution feature, that is, obvious growth occurs first, then gradually returns to stability, and the overall deformation is slow. (4) The total deformation amount is positively correlated with the sum of rainfall 15 days before the initiation of accelerated deformation and during accelerated deformation; the duration of deformation is positively correlated with the rainfall 10 days before the accelerated deformation stops.