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

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

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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°,

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is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found between

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and β; however, the average

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seems to slightly decrease with increasing k. The variability of

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is found to increase with k. Based on the cases studied in this work,

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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

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is obtained for k=0.8. For the remaining k values the variability of

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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.

Keywords

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

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