Deformation characteristics and mechanism of Mala paleo-landslide during the Miaowei reservoir initial impoundment period

Abstract

This study employs a multifaceted approach, encompassing field investigations, borehole surveys, surface deformation displacement monitoring, deep-seated deformation monitoring, and numerical simulation analysis, to conduct an exhaustive examination of the deformation processes and characteristics exhibited by the Mala Landslide. The findings elucidate a close correlation between the deformation of the Mala Landslide and the elevation of the reservoir water level. During the escalation of the reservoir water level, the landslide body progressively developed surface cracks, spanning from the frontal edge to the rear edge. The centre of the sliding body is situated in the central-lower downstream region, and presently, the landslide is undergoing a phase of comprehensive creep deformation. Due to the reservoir water level fluctuation rate being greater than the permeability coefficient, the deformation of the landslide displays a delayed response. As the reservoir water level reaches 1401 m during high-water operation, the two important ingredients, the buoyancy weight reduction effect and the influence of submerged reservoir water, significantly reduce the sliding resistance of the sliding mass, thereby exacerbating the deformation of the landslide. Following a comprehensive analysis of the findings, it can be firmly concluded that this landslide conforms to the characteristic traits of a typical buoyant force reduction type-retrogressive type landslide.