Formation mechanism and stability analysis of a landslide in altered ophiolite in the upper reaches of Jinsha River: A case study of the Duirongtong landslide

Abstract

Objective  The tectonic suture zone of the Qinghai-Tibet Plateau has a complex rock mass structure and special lithology combination and is thus prone for large landslides. However, many factors influence the formation and evolution of landslides in altered ophiolite. Their formation mechanism is not clear at present, which restricts an effective identification and disaster risk prevention.   Methods  Taking the Duirongtong (DRT) landslide in the Jinsha River tectonic suture zone as an example, field investigations, UAV mapping, geochronological analysis, ring-shear testing, and numerical simulation were performed to analyze the formation mechanisms of the landslide and evaluate the stability of the landslide deposits.   Results  The results show that: (1) The DRT landslide is a giant landslide formed in the late Pleistocene. The slope is mainly composed of basic-ultrabasic rocks, and several clay-altered ophiolitic bands are developed, forming a sliding-prone geo-structure. (2) The clay-altered ophiolite has low shear strength under natural conditions, and its shear strength drops sharply when exposed to water. The natural values of c and φ are 67.0 kPa and 20.3°, and the water-saturated values of cohesion(c) and angle of internal friction(φ) are 39.8 kPa and 13.83°. The DRT landslide is currently stable as a whole, but the leading edge of the landslide may experience movement under heavy rainfall. Based on numerical simulation, some preventive recommendations are proposed.   Conclusion  The study suggests that the formation and evolution of the DRT landslide are controlled by the combination of geological structure and clay-altered rock. [ Significance ] These findings have important implications for the slope stability analysis and disaster prevention in the tectonic suture zone of the Qinghai-Tibet Plateau