Abstract
Rock slopes contain numerous nonpenetrating intermittent joints which maintain stability under excavation disturbance. The tip interaction coefficient (IC) of parallel offset double cracks in a typical rock mass under unloading conditions was calculated in this study based on the superposition principle and fracture mechanics to determine the meso-influence law of intermittent joint interaction in the slope under the action of excavation. The influence of many factors on the said interaction was also analyzed theoretically. Lateral unloading tests were conducted on rock-like specimens with parallel offset cracks in addition to RFPA2D numerical simulation and theoretical analysis. The results show that a smaller length of rock bridge or staggered distance between the cracks results in more severe and sensitive interactions at the crack tip. The Type I interaction strength of the tip of the crack is not affected by the inclination angle of the crack, but shear failure gradually weakens as the angle changes. The shear failure of the tip of the crack is more sensitive to changes in the inclination angle when the cracks are closer to each other; the change is the most intense when α is about 60°. Lateral unloading test and RFPA2D numerical simulation results are in close agreement with the theoretical analysis, which validates the theoretical results. The current study shows the interaction of the parallel offset cracks in rock under unloading conditions and is conducive to the study of the meso-failure mechanism of the jointed rock slope in an open-pit mine under the action of excavation.
Highlights
An open-pit mine slope is subjected to rock mass unloading in the process of excavation
High stress concentration at the end of the intermittent joint may lead to the initiation, propagation, and penetration of cracks in the rock bridge which may cause sudden instability and macroscopic failure of the slope, and the rock slope instability mechanisms occur along existing discontinuities and as complex internal processes associated with shear or tensile fracture in the intact rock, in massive natural rock slopes and deep engineered slopes [1,2,3]
The propagation and interaction laws of parallel offset double cracks under unloading conditions were theoretically analyzed based on the multiple superposition principle and the relevant calculation method of SIF in fracture mechanics
Summary
An open-pit mine slope is subjected to rock mass unloading in the process of excavation. Meso-mechanical knowledge regarding the crack evolution laws and interaction between cracks and intermittent joints in the rock mass have crucial significance in terms of the failure mechanism of open-pit rock slopes under excavation. Such knowledge can be utilized to design safe, reasonable excavation schemes. Ere have been few previous studies on the propagation and evolution of parallel offset cracks and the interaction between cracks under unloading conditions, and most extant research centers on rock specimen testing and numerical simulation. The theoretical results were validated by comparison against lateral unloading test and RFPA2D numerical simulation results for similar rock-like materials
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