Research Article
Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests
Table 5
Mass fractions of fragments at different scales in coal and sandstone samples under different initial unloading confining pressures.
| Scale (mm) | Confining pressure (MPa) | Coal | Sandstone | 4 | 7 | 10 | 4 | 7 | 10 | 13 | 16 | 19 |
| 0.3 ≥ d | 0.030 | 0.023 | 0.015 | 0.023 | 0.017 | 0.013 | 0.010 | 0.007 | 0.005 | 0.6 ≥ d > 0.3 | 0.059 | 0.050 | 0.044 | 0.054 | 0.045 | 0.039 | 0.037 | 0.028 | 0.032 | 1.18 ≥ d > 0.6 | 0.100 | 0.083 | 0.061 | 0.076 | 0.068 | 0.063 | 0.046 | 0.050 | 0.041 | 2.36 ≥ d > 1.18 | 0.139 | 0.127 | 0.088 | 0.116 | 0.105 | 0.097 | 0.090 | 0.094 | 0.089 | 4.75 ≥ d > 2.36 | 0.151 | 0.155 | 0.142 | 0.147 | 0.133 | 0.156 | 0.143 | 0.148 | 0.141 | 9.5 ≥ d> 4.75 | 0.162 | 0.176 | 0.181 | 0.163 | 0.185 | 0.171 | 0.179 | 0.171 | 0.161 | 13.2 ≥ d> 9.5 | 0.170 | 0.179 | 0.219 | 0.190 | 0.206 | 0.198 | 0.196 | 0.201 | 0.194 | 19 ≥ d > 13.2 | 0.190 | 0.207 | 0.251 | 0.232 | 0.242 | 0.263 | 0.300 | 0.301 | 0.337 |
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