Abstract
The geometric distribution of initial damages has a great influence on the strength and progressive failure characteristics of the fractured rock mass. Initial damages of the fractured rock were simplified as parallel cracks in different geometric distributions, and then, the progressive failure and acoustic emission (AE) characteristics of specimens under the uniaxial compression loading were analyzed. The red sandstone (brittle materials) specimens with the parallel preexisting cracks by water jet were used in the tests. The energy peak and stress attenuation induced by the energy release of crack initiation were intuitively observed in the test process. Besides, three modes of rock bridge coalescence were obtained, and wing crack was the main crack propagation mode. The wing crack and other cracks were initiated in different loading stages, which were closely related to the energy level of crack initiation. The propagation of wing crack (stable crack) consumed a large amount of energy, and then, the propagation of shear crack, secondary crack, and anti-wing crack (unstable crack) was inhibited. The relationship between the crack propagation mode and the geometric distribution of existing cracks in the specimen was revealed. Meanwhile, the strength characteristic and failure mode of fractured rock with the different geometric distributions of preexisting crack were also investigated. The energy evolution characteristics and crack propagation were also analyzed by numerical modeling (PFC2D).
Highlights
Rock mass as the main geological body has a lot of randomly distributed macroscopic and microscopic initial damages [1, 2]. e propagation and unstable failure of initial damage can induce engineering geological disasters under the mining influence [3,4,5]. e initial damage can be conceptualized as rock fracture in the laboratory, and the fracture instability characteristics and progressive failure of rock mass with different geometric distributions have a great significance for the prediction and control of fractured rock instability disasters [6]
Hao et al [22, 23] studied the time-dependent development of the excavation damaged zone (EDZ) around underground diversion tunnels in a columnar jointed rock mass and studied the fracture behaviour and crack propagation features of coal under coupled static-dynamic loading conditions. e single crack under the dynamic loading and tensile crack fatigue failure has been highlighted in most recent research of rock fracture propagation behaviors, while the complex crack propagation characteristics were rarely studied
According to stress strain characteristics, the test process was divided into three stages: initial compression, elastic deformation, and peak failure, as shown in Figure 4. e crack propagation was concentrated in the peak failure stage. e wing crack of Group 1 and Group 3 was initiated in the elastic deformation stage, and axial stress decreased transitorily. e average stress of each group changed with geometry distributions. e average peak stress of Group 2 (15.11 MPa) was the lowest one, and that of Group 1 (23.12 MPa) was the highest one
Summary
Rock mass as the main geological body has a lot of randomly distributed macroscopic and microscopic initial damages [1, 2]. e propagation and unstable failure of initial damage can induce engineering geological disasters under the mining influence [3,4,5]. e initial damage can be conceptualized as rock fracture in the laboratory, and the fracture instability characteristics and progressive failure of rock mass with different geometric distributions have a great significance for the prediction and control of fractured rock instability disasters [6]. E initial damage can be conceptualized as rock fracture in the laboratory, and the fracture instability characteristics and progressive failure of rock mass with different geometric distributions have a great significance for the prediction and control of fractured rock instability disasters [6]. Studies on the rock (sandstone, marble, etc.) fracture propagation were mainly performed under different loading modes. Hao et al [22, 23] studied the time-dependent development of the excavation damaged zone (EDZ) around underground diversion tunnels in a columnar jointed rock mass and studied the fracture behaviour and crack propagation features of coal under coupled static-dynamic loading conditions. E single crack under the dynamic loading and tensile crack fatigue failure has been highlighted in most recent research of rock fracture propagation behaviors, while the complex crack propagation characteristics were rarely studied. Research results provide a reference for the prevention and control of rock mass instability under similar engineering conditions (uniaxial compression loading and parallel joints)
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