Abstract
Weak intercalation forms a sliding zone after long-term geological evolution and deterioration and plays an essential role in controlling massive layered bedrock landslides. In order to determine the formation process of such a sliding zone, the study took the Jiweishan Mountain landslide as an example. It analyzed the distribution and developmental regularities of the weak intercalation. Its three evolutionary stages were divided: the original soft rock, the interlayer shear zone, and the sliding zone. In addition, the study comparatively studied the evolutionary characteristics of weak intercalation through the laboratory test of the physical properties, physicochemical properties, and physical mechanics properties of three stages. The result indicated that, in terms of the evolution of mineral composition, the clay mineral content increased significantly, with the mean value up from 4.4% to 16.9%. In terms of the microstructure evolution, the inter-granular connection became weaker, the microstructure turned loose from dense structures, the porosity and joint fissures were increased, the density was decreased by 5%–6%, and the porosity was up by 108%. From the evolutionary process of the physicochemical properties, the total content of exchangeable salt was the highest in the original rock, followed by the sliding zone, whereas the interlayer shear zone exhibited the lowest value. The organic matter content was gradually increased, and the entire evolutionary environment was weakly alkaline. Concerning the evolutionary process of shear strength, the internal friction angle of the weak intercalation was decreased from 57.58° to 29.63°, and the cohesion, which had prominent creep characteristics, was reduced from 585 kPa to 96 kPa. Based on these data, the study also analyzed the residual sliding thrust of the largest main section of the driving block in the Jiweishan landslide. The residual sliding thrust increased as the long-term strength parameter decreased. When the internal friction angle ϕ < 25° and cohesion c < 129 kPa, the residual sliding thrust was greater than zero and reached a maximum value of 9.7×104 kN/m. The conclusions of this study provided an essential reference for the further research on the development and mechanism of layered rockslides controlled by weak intercalations.
Published Version
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