The freeze-thaw weakening of rock structural planes on slope stability: effects of cycle numbers and burial depth

This study investigates rock slopes in cold-region open-pit mines through integrated laboratory experiments and numerical simulations, revealing the freeze‒thaw weakening laws of structural planes and fractured rock masses. The stability and failure patterns of both fractured rock mass slopes and structural plane-controlled slopes are analyzed under the coupled effects of the number of freeze‒thaw cycles and burial depth. The results indicate that the number of freeze‒thaw cycles dominates structural plane weakening, causing shear strength reductions of 5.19% (2 cycles), 12.60% (5 cycles), 24.75% (10 cycles) and 36.69% (20 cycles) at 0.10 m burial depth relative to natural conditions. For fractured rock masses, the cohesion and internal friction angle deteriorate exponentially with increasing number of cycles and shallower depths. Concurrently, slope mechanical parameters develop progressively distinct layered characteristics during freeze‒thaw cycles. Fractured rock mass slopes consistently exhibit less freeze‒thaw weakening than structural plane-controlled slopes, with failures occurring at 28 and 37 cycles. Under freeze‒thaw cycles, potential slip surfaces in fractured rock mass slopes progressively migrate towards the slope face with developing higher parallelism, causing an average depth of 7.42 m to shallow after 20 freeze‒thaw cycles. These findings provide theoretical support for stability assessments of geotechnical engineering in cold regions.