Analysis of Mechanical Strength and Failure Morphology of Prefabricated Closed Cracked Rock Mass Under Uniaxial Compress
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ORIGINAL PAPER
Analysis of Mechanical Strength and Failure Morphology of Prefabricated Closed Cracked Rock Mass Under Uniaxial Compression Longyu Zhang . Jiming Zhu
Received: 16 April 2020 / Accepted: 30 April 2020 Ó Springer Nature Switzerland AG 2020
Abstract In order to obtain the mechanical strength and failure characteristics of fractured rock masses with prefabricated closed crack, Based on the indoor uniaxial compression test, the parameters of the prefabricated closed crack specimens were calibrated. The PFC3D software was used to perform the uniaxial compression simulation test on the prefabricated closed crack rock-like material. The change rules of mechanical parameters of fractured specimens with different prefabricated closed cracks and the failure morphology of rock specimens were obtained. The results showed that: most of the parameters such as elastic modulus, secant modulus, deformation modulus, peak strength and peak strain of the specimen showed a downward trend with the increase of crack diameter and inclination. Among all the parameters, the change of crack inclination angle and diameter had the greatest impact on the Peak strength, and the least influence on Secant modulus; Micro cracks mainly occurred around the prefabricated crack, and when the diameter of prefabricated cracks was small, micro cracks outside the prefabricated cracks were more likely to appear; With the increase of crack diameter and inclination angle, the stress at the moment when the first micro crack appears first decreased and then
L. Zhang J. Zhu (&) Department of Resources and Civil Engineering, Shandong University of Science and Technology, Taian 271019, China e-mail: [email protected]
increased; The growth process of the number of micro cracks had gone through three stages: the stage of no micro cracks, the stage of unstable growth of micro cracks and the stage of rapid growth of micro crack. Keywords Uniaxial compression Crack parameters Micro crack Mechanical strength Stress–strain curve Failure morphology
1 Introduction The initiation, expansion and penetration of cracks inside the rock were the triggers for engineering accidents (Yang et al. 2005). At present, the research on the laws of prefabricated crack propagation mainly included theoretical analysis, laboratory test and numerical simulation. There were many assumptions in theoretical analysis, the research process was complicated and it was not easy to get an accurate solution. The main materials used in laboratory tests were rock-like materials (Zhang et al. 2019; Bobet and Einstein 1998), primary rocks (Xie et al. 2011; NolenHoeksema 1987) and brittle materials such as resin (Fu et al. 2013; Brace and Bombolakis 1963). There were differences in the sampling of primary rocks, which was difficult to compare and analyze. There was a certain difference in fracture mechanical properties between single crystal material and rock (Atkinson 1984). The rock-like materials for prefabricated crack
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