The characteristics of crack existence and development during rock shear fracturing evolution
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ORIGINAL PAPER
The characteristics of crack existence and development during rock shear fracturing evolution Xiangxin Liu 1,2
&
Lixin Wu 3 & Yanbo Zhang 2 & Shuzhi Wang 2 & Xulong Yao 2 & Xianzhen Wu 4
Received: 6 June 2019 / Accepted: 30 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Rock shear fracturing occurs frequently in engineering sites, such as underground tunnels and rock slopes. One main factor is that the multiple presence of crack is complicated, especially in terms of crack status. This study aims to investigate the crack status from both crack existence and development. Rock fracturing is carried out by shear loading. Acoustic emission (AE) monitoring system and CCD camera are used to catch the characteristics of crack evolution. Results demonstrate that crack status is influenced by rock physical properties and its stress boundary, there exists a positive correlation between normal force and crack geometry (such as the angle of en echelon crack). Crack existence follows a distribution of “the whole size of en echelon crack and the local region of pinnate crack” in terms of spatial-temporal aspects. Crack development manifests the characteristics of “Inheritance and Variability”. Keywords Shear fracturing . Crack status . Crack existence . Crack development
Abbreviation AE Acoustic emission AF Average frequency, which is defined as AE counts divided by duration time RA RA value, which is defined as rise time divided by maximum amplitude
Introduction Rock shear fracturing is greatly influenced by rock mechanical properties and its stress boundary (Janach and Lan 1980; Brantut * Xiangxin Liu [email protected] * Lixin Wu [email protected] 1
College of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China
2
College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China
3
School of Geosciences and Info-physics, Central South University, Changsha 410083, China
4
School of Resource and Environmental Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China
et al. 2013; Rathnaweera et al. 2017). The process of brittle rock failure is an important aspect for the safety of underground engineering (Zhou 2005; Clayton 2010). The study of activation mechanism of small- and medium-scale brittle fault is significant not only for the prediction of disasters caused by mining but also for the process of earthquake preparation (Cheng et al. 2019). Many scholars focused on the characteristics of rock fracturing and the investigation of crack distributions. Peak shear strength and residual shear strength of rock joints within low number of cycles varied from those within high number of cycles (Hawkes and Mellor 1970; Zhou et al. 2015; Fathi et al. 2016; Liu et al. 2018). Different aperture shapes, sizes, normal stress, and shearing rates were considered to research the behaviors of unreinforced and geogrid-reinforced ballast at different rates of shearing. Interface shear stren
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