Abstract
Flaw is a key factor influencing failure behavior of a fractured specimen. In the present study, rectangular‐flawed specimens were prepared using sandstone to investigate the effect of flaw on failure behavior of rock. Open flaw and cylindrical hole were simultaneously precut within rock specimens using high‐pressure water jet cutting technology. Five series of specimens including intact, single‐hole‐alone, two‐hole‐alone, single‐hole and two‐flaw, and two‐hole and single‐flaw blocks were prepared. Uniaxial compressive tests using a rigid servo control instrument were carried out to investigate the fracture processes of these flawed specimens. It is observed that during loading, internal stress always intensively distributed at both sidewalls of open hole, especially at midpoint of sidewalls, so rock crumb flaking was firstly observed among all sandstone specimens containing single hole or two holes. Cracking around open hole is associated with the flaw inclination angle which was observed in Series III and V. Crack easily initiated at the tips of flaw with inclination angles of 0°, 30°, and 60° but hard for 90° in Series III and V. Rock burst was the major failure mode among most tested specimens, which generally induced new cracks and finally created crater shape. Additionally, due to extrusion between blocks, new shear or tensile cracks were generated and the rock specimen surface spalled. Eventually, four typical failure processes including rock crumb flaking, crack initiation and propagation, rock burst, and second rupture, were summarized.
Highlights
It is well known that rock mass is discontinuous and inhomogeneous due to numerous joints, cleavages, beddings, and faults presented within it. e increasing number of engineering practice, such as mining, tunneling, and hydraulic power station, has fueled growing research interests on fractured rock mass
Research has found that the axial strength of a rock specimen was closely related to flaw length and flaw inclination angle, and a number of relationships reveal that uniaxial compressive strength (UCS) of rock decreases with increasing flaw length
Uniaxial compressive tests were performed to investigate the failure process of flawed and holey specimens. e following conclusions can be established from the presented results in this study: (1) For hole-existent specimens without flaw, rock crumb flaking was firstly occurred at sidewalls, and its failure was blast-induced and usually created crater at stress-concentrated zone
Summary
It is well known that rock mass is discontinuous and inhomogeneous due to numerous joints, cleavages, beddings, and faults presented within it. e increasing number of engineering practice, such as mining, tunneling, and hydraulic power station, has fueled growing research interests on fractured rock mass. To model stress change and failure behavior around opening created by engineering construction, experimental and numerical approaches were widely used. Zhao et al [38] used experimental and numerical methods to study failure characteristics of rocklike materials with an open hole and found that peak strength was related to sample width and hole diameter. In the numerical studies of cracking process, a distinct element method, particle flow code, was widely used to simulate crack initiation and propagation of single flaw or multiflaw specimens under uniaxial or biaxial compression loading [7, 44, 45]. Experimental and numerical approaches were employed to investigate the failure process of rock specimens containing both flaw and hole under uniaxial compressive loading. Experimental and numerical approaches were employed to investigate the failure process of rock specimens containing both flaw and hole under uniaxial compressive loading. e study aims to investigate the interaction between hole and flaw location and the influence of the inclination angle of flaw around hole on cracking process, which contributes to good understanding of influence of flaw location and orientation on damaged zones of circular openings in rock mechanics
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