Abstract
Failure of underground structures, especially intersections, becomes more severe as the depth increases, which poses a new challenge for the safe construction and operation of deep rock engineering. To investigate the mechanical properties and fracture behavior of rock with an intersecting hole under compressive loads, a series of uniaxial compression tests was carried out on cuboid red sandstone specimens containing an intersecting hole with three types of shapes by digital image correlation (DIC) technique. The results showed that the existing hole inside specimens leads to almost a 50% reduction of mechanical parameters from that of intact ones, and this weakening effect is associated with the shapes of holes. Failure of specimens is a progressive process in which cracks, i.e., primary tensile cracks, secondary tensile cracks, and shear cracks, initiate from stress concentration zones, propagate along certain direction, and coalesce with each other into macrofractures. Both the real-time principal strain fields and horizontal displacement fields of specimens under compression could be visually displayed by DIC system, and they were in good consistency in characterizing the fracture behavior. Moreover, the propagation characteristics of primary tensile cracks were studied further by quantitatively analyzing the strain variation during the loading process, and the propagation mechanism of “open-close-reopen” of primary tensile cracks was explained in detail.
Highlights
Underground mining is a process of bringing earth minerals to the surface
We conducted a series of uniaxial compression tests on rock specimens containing an intersecting hole to investigate the effects of intersection types and the mechanical properties of specimens with open-hole defects were compared with intact specimens. e failure mechanism and crack behavior under the action of uniaxial compression stress were further analyzed in detail by means of digital image correlation (DIC) technique
A series of experiments was carried out to investigate the mechanical properties and fracture responses of sandstone containing an intersecting hole with different shapes under uniaxial compression
Summary
Underground mining is a process of bringing earth minerals to the surface. It is commonly understood that digging a large number of roadways or shafts into the earth to reach ore deposits is essential [1,2,3,4]. Erefore, studying the stability and failure mechanism of intersection structures is necessary, playing a significant role in support design of mines. In addition to roadway intersections, intersections between shafts and roadways are very common in mines He et al [23] studied the stress and displacement characteristics of the surrounding rock of pump chambers and found that the excavation sequence of “branch roadway first, main roadway second” had the least disturbance effect on the intersection structure. Cheng et al [26] further investigated the distribution of the mining-induced stress field and plastic zone of the intersection structure by numerical simulations and presented a joint support technology, i.e., anchor-netshotcrete for preliminary bracing and grouting for secondary support. We conducted a series of uniaxial compression tests on rock specimens containing an intersecting hole to investigate the effects of intersection types and the mechanical properties of specimens with open-hole defects were compared with intact specimens. e failure mechanism and crack behavior under the action of uniaxial compression stress were further analyzed in detail by means of digital image correlation (DIC) technique
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