Analysis of instability conditions and failure mode of a specialtype of translational landslide using a long-period monitoringdata: a case study of the Wobaoshi landslide (Bazhong city, China)

Abstract. A translational landslide comprising nearly horizontal sand and mud interbed was widely developed in the Ba river basin of the Qinba–Longnan mountain area. Scholars have conducted theoretical research on this rainfall-induced landslide; however, owing to the lack of landslide monitoring engineering and data, demonstrating and validating the theoretical research wasdifficult. This study considered a translational landslide with an unusual morphology: the Wobaoshi landslide, which is located in Bazhong city, China. First, the formation conditions of this landslide were ascertained through field exploration, and the deformation and failure characteristics of the plate-shaped sliding body were analyzed. Then, long-period monitoring engineering was conducted to obtain multi-parameter monitoring data, such as crack width, rainfall intensity, and pore-water pressure. Finally, through the mechanical model analysis of the multi-stage sliding bodies, the calculating formula of the maximum height of the multi-stage plate girders, hcr, was derived，and the long-period monitoring data were used to verify its accuracy. Combined with numerical simulation and calculations, the deformation and failure modes of the plate-shaped sliding bodies were analyzed and explored. In this paper, the multi-parameter monitoring data proved that the stability of the sliding body is affected greatly by the rainfall intensity and pore-water pressure and the pore-water pressure in the crack is positive for the beginning of the plate-shaped sliding bodies, and an optimization monitoring method for this type of landslide was proposed. Therefore, this paper has theoretical and practical significance for the intensive study of translational landslides in this area.