Cause analysis and control measures of landslide in Yibin well site of Sichuan Province

An oil and gas well site in Gongxian County of Yibin in Sichuan Province is located on the ancient sliding accumulation body. Due to the excavation of the well site operation platform, the ancient sliding accumulation body was partially revived, and the ancient sliding accumulation body collapsed in March 2018, which was in the process of creeping deformation. According to the field survey, the landslide at the well site is tongue-shaped in plane, with a length of about 200 m and a width of about 150 m. The height difference between the front and rear edges of the landslide is about 35 m, and the thickness of the drilling structure slide is about 8m. It is estimated that the volume of the landslide is about 27×10⁴ m³. The well site landslide is divided into four deformation areas on the plane, and a large number of tension fractures and uplift cracks were developed on the well site platform and the middle and back of the slide body, with cracks width of 4 to 8 cm and uplift height of 21 to 35 cm. The special terrain condition and soil layer structure cause the multi-layer sliding surface of the landslide. Considering that the landslide at the well site belongs to the situation of side-slip treatment, the selected treatment plan is mainly anti-slide pile + anchor cable + net spraying between piles + pile top connecting beam + retaining wall + cut-off drainage ditch, and the plan has passed the post-monitoring verification. The results show that the horizontal and vertical displacements of the anti-sliding piles at each monitoring point gradually converge and tend to be stable, and the stress of the anchor cable is in a gentle state with stable of 14 kN. This control scheme has good applicability, and provide design reference for related projects.