Crack initiation stress and strain of jointed rock containing multi-cracks under uniaxial compressive loading: a particle flow code approach

FAN Xiang(范祥)^{1, 2}, KULATILAKE P H S W², CHEN Xin(陈新)³, CAO Ping(曹平)¹

(1. School of Resources and Safety Engineering, Central South University, Changsha 410083, China;
2. Rock Mass Modeling and Computational Rock Mechanics Laboratories,
University of Arizona, Tucson AZ 85721, USA;
3. School of Mechanics and Civil Engineering, China University of Mining and Technology (Beijing),
Beijing 100083, China)

Abstract:The ratio of crack initiation stress to the uniaxial compressive strength (S_CI,B/S_UC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength ( ) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing’s under uniaxial loading using PFC^3D. The following findings are obtained: S_CI,B/S_UC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°, is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found between and β; however, the average seems to slightly decrease with increasing k. The variability of is found to increase with k. Based on the cases studied in this work, ranges between 0.3 and 0.5. this range is quite close to the range of 0.4 to 0.6 obtained for S_CI,B/S_UC,B. The highest variability of ± 0.12 for is obtained for k=0.8. For the remaining k values the variability of can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of S_CI,B/S_UC,B.

Key words:jointed rock; multi flaws; uniaxial loading; PFC^3D model; crack initiation stress (S_CI,B); axial strain at crack initiation stress