Experimental investigations on mechanical performance of rocks under fatigue loads and biaxial confinements
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Experimental investigations on mechanical performance of rocks under fatigue loads and biaxial confinements DU Kun(杜坤)1, 2, LI Xue-feng(李雪锋)1, YANG Cheng-zhi(杨成志)1, ZHOU Jian(周健)1, CHEN Shao-jie(陈绍杰)3, MANOJ Khandelwal4 1. School of Resources and Safety Engineering, Central South University, Changsha 410083, China; 2. Advanced Research Center, Central South University, Changsha 410083, China; 3. Mining Disaster Prevention and Control Ministry Key Laboratory, Shandong University of Science and Technology, Qingdao 266590, China; 4. School of Engineering, Information Technology and Physical Sciences, Federation University Australia, Ballarat 3350, Australia © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: In this research, a series of biaxial compression and biaxial fatigue tests were conducted to investigate the mechanical behaviors of marble and sandstone under biaxial confinements. Experimental results demonstrate that the biaxial compressive strength of rocks under biaxial compression increases firstly, and subsequently decreases with increase of the intermediate principal stress. The fatigue failure characteristics of the rocks in biaxial fatigue tests are functions of the peak value of fatigue loads, the intermediate principal stress and the rock lithology. With the increase of the peak values of fatigue loads, the fatigue lives of rocks decrease. The intermediate principal stress strengthens the resistance ability of rocks to fatigue loads except considering the strength increasing under biaxial confinements. The fatigue lives of rocks increase with the increase of the intermediate principal stress under the same ratio of the fatigue load and their biaxial compressive strength. The acoustic emission (AE) and fragments studies showed that the sandstone has higher ability to resist the fatigue loads compared to the marble, and the marble generated a greater number of smaller fragments after fatigue failure compared to the sandstone. So, it can be inferred that the rock breaking efficiency and rock burst is higher or severer induced by fatigue loading than that induced by monotonous quasi-static loading, especially for hard rocks. Key words: biaxial confinements; fatigue loading; acoustic emission; fragments; intermediate principal stress Cite this article as: DU Kun, LI Xue-feng, YANG Cheng-zhi, ZHOU Jian, CHEN Shao-jie, MANOJ Khandelwal. Experimental investigations on the mechanical performance of rocks under fatigue loads and biaxial confinements [J]. Journal of Central South University, 2020, 27(10): 2985−2998. DOI: https://doi.org/10.1007/s11771-020-4523-7.
1 Introduction The underground engineering excavation changes the initial stress field of rocks in the vicinity to a secondary stress field [1−3]. The rocks
located at the range of the secondary stress field is defined as engineering surrounding rock (ESR). The most affected part of the ESR by underground excavation is termed as excavation damaged zone (EDZ), which is the closest to the underground e
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