Variable-angle shear mechanical properties and microseismic signal characteristics of bedded limestone under different water-bearing states

Abstract

[Objective] The stability and failure modes of bedding rock slopes are closely related to the shear mechanical behavior of layered rock masses. To thoroughly reveal the underlying mechanisms, the effects of different shear angles and water-bearing states on the shear mechanical behavior of bedded limestone are investigated. [Methods] Variable-angle shear tests were conducted, combining with digital image correlation(DIC) and microseismic monitoring techniques, on bedded limestone specimens under both natural and saturated water-bearing states at different shear angles(30°~60°). Their mechanical properties, strain field evolution, and microseismic signal characteristics were systematically studied. [Results] The result demonstrated that:(1) with increasing shear angle, the peak shear stress, normal stress, and shear stress of the specimens gradually decreased, while the failure mode transitioned from shear fracture of the rock matrix to slip along the bedding planes.(2) At lower shear angles, the specimens tended to develop shear-tensile composite fractures with relatively fragmented failure patterns. As the shear angle increased, the effects of normal stress weakened, and the failure mode gradually transformed into a single slip mode dominated by shear along the bedding planes.(3) Under the natural state, microseismic activity exhibited a clear sequence of “active-quiet-precursor-mainshock” with high signal peaks, indicating typical brittle failure. Under the saturated state, the lubricating effects of water caused microseismic activity to remain continuously active, but the signal peaks were significantly lower, demonstrating microseismic signal characteristics of a transition from brittle to plastic failure.(4) The shear angle dominated the macroscopic deformation and failure mode of bedded limestone specimens. At lower angles, microseismic activity was dispersed with high cumulative counts, while at higher angles, microseismic precursor signals became concentrated with a significant quiet period, [Results]ing in more sudden failure. [Conclusion] The research findings provide theoretical and data support for stability evaluation and disaster early warning of bedding rock slopes under rainfall conditions by revealing the variable-angle shear mechanical properties and microseismic signal characteristics of bedded limestone under different water-bearing states.

Keywords

bedded limestone / variable-angle shear / shear angle / water-bearing state / mechanical properties / microseismic signal characteristics / rainfall / disaster early warning