Abstract
Abstract This research took the Langjia landslide in Qinghai Province of China as an example to explore the failure mechanism and mode of deep relaxation rockslide at cold and arid areas of the plateau under the influence of temperature difference, rainfall. Studies showed that deep relaxation tension cracks are the main precondition of the occurrence of the landslide, and the main triggering factor was the strong weathering and disintegration of argillaceous cemented conglomerate on sliding surface. Affected by rainfall, snow melting, and temperature, the water trapped in tensile cracks froze to ice in winter to accelerate the development of cracks and melt into water in spring and summer to accelerate the weathering process. The process led to forming a sliding surface of mud rock with gravel by weathering the argillaceous cemented conglomerate along the cracks, which was confirmed by field investigation after occurrence of the landslide. For this special failure type, calculation formula on considering rolling friction, sliding friction, and bottom shear stress was proposed, and the influence of shear stress on sliding surface on landslide stability under the seepage caused by rainfall and summer melt water when landslide occurred was discussed. The calculation results of three-dimensional numerical simulation and improved Sarma’s method on considering the hydrodynamic action on relaxation slope stability are consistent with the actual situation.
Highlights
Landslides often happened in cold and arid relaxation rock slope area due to excavation or natural climate conditions, especially in the construction of water conservancy and hydropower projects
We revealed the influence of temperature and rainfall on the weathering process of conglomerate rock mass under the condition of relaxation crack development, and we discussed the influence of gravel produced after weathering conglomerate rock mass on the change of the landslide sliding mode
Two groups of relaxation cracks were developed on the slope; one group is the relaxation shear joints with a slow angle, which is close to the bottom of the slope, and this group of cracks generally formed the sliding surface (Figure 4) of the landslide mass
Summary
Landslides often happened in cold and arid relaxation rock slope area due to excavation or natural climate conditions, especially in the construction of water conservancy and hydropower projects. Most scholars have been devoted to the study of relaxation rock engineering characteristics or relaxation mechanism [1,2,3,4], but detailed studies of relaxation rock mass slope failure mechanisms in cold and arid area are sparse, especially considering the hydrodynamic force. In the construction of water conservancy and hydropower station in Western China, the stability of relaxation rock slope was often encountered at dam foundation or bank slope of the reservoir area. The rivers and main mountains extend northwest, with steep terrain and crisscross gullies. The mountains on both sides of the river valley are steep with a slope angle of about 50°. The highest elevation of both sides is 2750-2800 m, and the bottom elevation of the river is 2590 m-2610 m, which is caused by tectonic erosion and accumulation
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