Model experimental study of deformation and failure mechanism of low-angled slopes with interbedding of soft and hard rocks

A lab model experiment of low-angled slope with interbedding of soft and hard rock is designed on the basis of geological analysis and similarity theory. The lab test is based on Peng Jiawan slope at Yi-Ba highway which has interbedding of soft and hard rocks with low dip angle. In the model tests, slope excavation tests are used to simulate the engineering excavation (or valley incision); and the water injection softening processes are used to simulate the rainfall infiltration. The results show: under both excavation and rainfall infiltration conditions, the deformation modes of the slope are sliding-tension at first and overall creep-slippage in the latter; and the failure mode is overall slip failure along the sliding zone of deep soft rock. Strictly speaking, the deformation of hard rock strata differs from the deformation of soft rock strata. Hard rock deforms mainly in sliding-tension but soft rock deforms mainly in overall creep-slippage. Changes of the condition of deep soft rock affect the total stability of the interbedding slope mostly. Both excavation and rainfall infiltration would lead to decline of stability of the slope. The free surfaces and micro-fissures induced by excavation are the basis triggering slope failure, and the rainfall provides incentives to the slope failure.