Experimental study on unloading induced shear performances of 3D saw-tooth rock fractures

Qian Yin ¹Xinxin Nie ¹Jiangyu Wu ²Qi Wang ³Kaiqi Bian ¹Hongwen Jing¹

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作者信息

1. State Key Laboratory for Geomechanics&Deep Underground Engineering,China University of Mining and Technology,Xuzhou 221116,China
2. State Key Laboratory for Geomechanics&Deep Underground Engineering,China University of Mining and Technology,Xuzhou 221116,China;State Key Laboratory of High Performance Civil Engineering Materials,Jiangsu Research Institute of Building Science Co.,Ltd.,Nanjing 210008,China;Department of Materials,University of Oxford,Oxford OX13PH,UK
3. State Key Laboratory for Geomechanics&Deep Underground Engineering,China University of Mining and Technology-Beijing,Beijing 100083,China
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Abstract

A fractal model governing saw-tooth fractures was first introduced to replicate sandstone samples con-taining an inclined 3D penetrating rough fracture surface with various joint roughness coefficients (JRC). In conventional triaxial compression, the peak strength for fractured samples increased with both confin-ing pressure and JRC. During the unloading confining pressure process, the normal stress of fractures declined but the shear stress increased, resulting in shear sliding of fractures. The shear displacement of fractures exponentially increased, and the positive normal displacement decreased gradually to nega-tive values under coupling effects of shear contraction caused by normal stress and shear dilation due to climbing effects of fractures. Transition from quasi-static to dynamic sliding of the fractures was identi-fied. The sliding resistance duration increased with confining pressure but decreased with JRC. After pre-peak unloading, the fracture surfaces presented a more significant surface wear response and JRC values decreased by 1.70％–59.20％due to more remarkable asperity degradation compared with those after con-ventional triaxial compression. The theoretical model for shear strength of fractures was established through improving the Ladanyi&Archambault model by introducing the relations between normal stress and surface wear ratios of fractures, which agreed well with the experimental results.

Key words

Saw-tooth fracture surfaces/Pre-peak unloading/Shear sliding/Normal displacement/JRC values

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基金项目

National Natural Science Foundation of China(52174092)

National Natural Science Foundation of China(51904290)

National Natural Science Foundation of China(52004272)

National Natural Science Foundation of China(52274145)

Natural Science Foundation of Jiangsu Province,China(BK20220157)

Natural Science Foundation of Jiangsu Province,China(BK20200660)

Fundamental Research Funds for the Central Universities,China(2022YCPY0202)

Xuzhou Science and Technology Project,China(KC21033)

Xuzhou Science and Technology Project,China(KC22005)

Yunlong Lake Laboratory of Deep Underground Science and Engineering Project,China(104023002)

出版年

2023

矿业科学技术学报(英文版)

中国矿业大学

矿业科学技术学报(英文版)

CSTPCDCSCD北大核心EI

影响因子：1.222

ISSN：2095-2686

被引量2

参考文献量8

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