Abstract
The propagation and coalescence of numerous discontinuous joints significantly contribute to landslide instability during excavation unloading. The tip expression of stress intensity factors of two collinear unequal length cracks in a typical rock mass under unloading conditions was calculated 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 effects of many factors on this interaction were also analyzed theoretically. Unloading tests were conducted on rock-like specimens with two collinear unequal length cracks in addition to numerical simulation and theoretical analysis. The results show decreased interaction between the two cracks with increased crack distance, increased influence of the main crack on a secondary crack with increased length of the main crack, and decreased influence of the secondary crack on the main crack with decreased length of the secondary crack. Wing tensile cracks first appear at the tip of flaws, and the propagation of these cracks occurs with the generation of secondary tensile cracks and shear cracks during unloading. Propagation and coalescence between cracks lead to tension and shear mixed failure of a rock bridge, and tensile cracks appear near the unloading surface. The axial initiation and peak stress of a crack increase with increased flaw distance, and the theoretical calculations were confirmed by lateral unloading test results.
Highlights
Numerous discontinuity cracks in rock slopes control the stability and failure mode of a rock slope
When the crack distance is equal to the length of the secondary crack, the main crack propagation is barely impacted by small crack
When the crack distance is equal to the length of the main crack, secondary crack propagation is little affected by the main crack
Summary
Numerous discontinuity cracks in rock slopes control the stability and failure mode of a rock slope. At the end of a discontinuity plane in a rock mass, high-stress concentration occurs during of rock slope excavation and unloading. This stress leads to crack propagation and coalescence and can further evolve into sudden local or global instability failure of the macroscopic upper slope, presenting a significant threat to the surrounding environment and operators [1, 2]. Kachanov [6] further analyzed the interactions of multiple cracks and proposed the expression of stress intensity factors at the tips of cracks based on a simplified pseudo-traction method, for a large crack distance, this method gives a significant calculation error. Qing and Yang [9] proposed a Geofluids new method to study multicrack interaction in infinite plates that incorporated aspects of both the alternating iteration method and the classical Kachanov method
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