Abstract:

Soft-hard alternant strata slopes formed by the interbedding of sandstone and mudstone or the mudstone imbedded in thick sandstones are distributed widely in the Three Gorges area. Cavities are formed by differential weathering between sandstone and mudstone and they can cause collapse of slopes. Firstly, mechanism of collapse of high slopes is studied from the aspects, such as the topographical features, lithologic characters, combination of structural surfaces, effects of rainfall and the weathering effects. Differential weathering is the main reason for the collapse of high slopes. Secondly, according to field surveys, failure mechanisms of high slope collapse are classified into toppling, sliding, creeping-tension, cantilever-tension and staggered breaking. Sketch maps of failure were generalized according to the failure mechanism. Forming process of collapse is determined by the numerical simulation. The failure process of collapse is mudstone spalling, cavity, sandstone crack opening, tilting of dangerous rock mass, toppling cillapse and rockfall deposite. Lastly, supporting measures were put forward against all the failure modes of high cutting slopes in the Three Gorges area. Research results are significant in the prevention and treatment of geo-hazards of the Three Gorges reservoir area.

Key words: soft-hard alternant strata, collapse, differential weathering, failure mechanism, discrete element numerical simulation, supporting measures