LI X L, DIAO H, CHEN C, et al.Improvement and verification of crack propagation prediction theory for rock materials under compressive load[J].Journal of Henan Polytechnic University(Natural Science) ,2024,43(5):163-172.

doi:10.16186/j.cnki.1673-9787.2023070006

Received:2023/07/05

Revised:2023/09/28

Published:2024/07/31

Improvement and verification of crack propagation prediction theory for rock materials under compressive load

LI Xiulei1, DIAO Hang2, CHEN Chen2, HUANG Feng2, LING Tianqing2, ZENG Bin1

1.School of River and Ocean Engineering，Chongqing Jiaotong University，Chongqing  400074，China;2.School of Civil Engineering，Chongqing Jiaotong University，Chongqing  400074，China

Abstract: Objectives The objective was to improve the accuracy of crack propagation prediction for rock materials by addressing deficiencies in the traditional maximum circumferential stress criterion （MTS criterion）， which disregarded the non-singular stress term （T-stress） in the crack tip’s stress field and the crack geometrical properties. Methods Based on the conventional MTS criterion， a new fracture criterion for non-closed fractures in rocks was established by considering the effects of T-stress and fracture geometry properties on the fracture tip stress field. Uniaxial compression tests were conducted on rock specimens with non-closed cracks in the center. The predicted criterion values were compared with the measured crack angle （θ）， and the influence of fracture geometry and T-stress on crack initiation and the crack tip stress field was analyzed to assess the validity of the proposed criterion.  Results The results of the research indicated that only considering fracture geometry features led to an increase in the crack width-length ratio （b/a）， causing a rise in the stress intensity factor （K_I）. This increase resulted in tension fractures forming due to tensile action at the fracture tip， thereby increasing the type I cracks in the composite fracture. When the geometric characteristics of the crack and T-stress were introduced simultaneously， an increase in the crack width ratio （b/a） reduced the crack angle θ and increased the maximum peripheral stress （σ_θ）_max. With the introduction of T-stress， the crack starting angle （θ） and the crack starting load are closer to the actual value， then the T-stress plays a crucial role in suppressing crack initiation. Additionally， the crack starting angle （θ） gradually transitioned from positive to negative cracking with the increase of the crack dip angle （β）.  Conclusions The crack initiation criterion， considering T-stress and crack geometry， can more accurately predict the crack initiation angle （θ） within the range of 0° to 60° of the crack dip angle （β）.

Key words:fracture criterion;non-closed crack;-stress;crack geometric properties;crack initiation angle