Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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Transactions of Nonferrous Metals Society of China

Vol. 29    No. 7    July 2019

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Unloading responses of pre-flawed rock specimens under different unloading rates
Xi-bing LI1, Zheng-hong CHEN1, Lei WENG2, Chong-jin LI1

1. School of Resources and Safety Engineering, Central South University, Changsha 410083, China;
2. School of Civil Engineering, Wuhan University, Wuhan 430072, China

Abstract:Based on the stress redistribution analysis of rock mass during the deep underground excavation, the unloading process of pre-flawed rock material was simulated by distinct element method (DEM). The effects of unloading rate and flaw inclination angle on unloading strengths and cracking properties of pre-flawed rock specimens are numerically revealed. The results indicate that the unloading failure strength of pre-flawed specimen exhibits a power-function increase trend with the increase of unloading period. Moreover, combined with the stress state analysis on the flaws, it is found that the unloading failure strength increases with the increase of flaw inclination angle. The cracking distribution of pre-flawed specimens under the unloading condition closely depends on the flaw inclination angle, and three typical types of flaw coalescence are observed. Furthermore, at a faster unloading rate, the pre-flawed specimen experiences a sharper and quicker unloading failure process, resulting in more splitting cracks in the specimens.


Key words: deep underground excavation; stress unloading; unloading rate; flaw inclination angle; distinct element method (DEM)

ISSN 1004-0609
CN 43-1238/TG

ISSN 1003-6326
CN 43-1239/TG

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