An Improved Crack Initiation Stress Criterion for Brittle Rocks under Confining Stress

2nd International Symposium on Resource Exploration and Environmental Science

生态环境科学

Wei, Lai^1,2 ; Liu, Quansheng^1 ; Liu, Xuewei^1

State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan

430071, China^1

University of Chinese Academy of Science, Beijing

100049, China^2

关键词: Confining stress;    Damage threshold;    Fracturing mechanisms;    Frictional components;    High confinement;    Inflection points;    Rock failure process;    Tri-axial compression tests;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/170/2/022141/pdf
DOI  :  10.1088/1755-1315/170/2/022141

学科分类：环境科学（综合）

来源: IOP

【 摘 要 】

The stress level associated with crack initiation is an important damage threshold in rock failure process, which can be applied in the prediction of brittle failure in tunnels. In the present study, the uniaxial and triaxial compression tests are conducted on two sets of hard sandstones, while the dilation strains and AE counts are employed to characterize the crack accumulation. The crack initiation stress is then determined through the inflection point on strain and AE curves. Furthermore, two crack initiation modes: the splitting mode for low confinements and the sliding mode for high confinements are presented by analysing the fracturing mechanism. Based on the derivation of maximum tensile stress around the rock defects, an improved crack initiation criterion is proposed to predict the σci of confined rocks. In the new criterion, the frictional components on crack surface are considered by introducing the parameter mci , which can be applied for various types of rocks as well. At last, the triaxial compression test data of different rock types are reviewed to verify the reliability and applicability of the new criterion. The results indicate that the new criterion can predict the crack initiation stress of confined rock with high accuracy.