Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests

<table class="table-group" id="tab2"><tr><td><table class="table"><tr><td class="thead-hr" colspan="3"><hr/></td></tr><tr class="thead"><td class="align_left">Lithology</td><td class="align_center"><i>σ</i><sub>3</sub> (MPa)</td><td class="align_center"><i>σ</i><sub>1</sub>–<i>σ</i><sub>3</sub> (MPa)</td></tr><tr><td class="thead-hr" colspan="3"><hr/></td></tr><tr><td class="align_left" rowspan="3">Coal</td><td class="align_center">4</td><td class="align_center">33.19</td></tr><tr><td class="align_center">7</td><td class="align_center">39.21</td></tr><tr><td class="align_center">10</td><td class="align_center">50.34</td></tr><tr><td class="align_left" colspan="3"><hr/></td></tr><tr><td class="align_left" rowspan="6">Sandstone</td><td class="align_center">4</td><td class="align_center">144.36</td></tr><tr><td class="align_center">7</td><td class="align_center">153.19</td></tr><tr><td class="align_center">10</td><td class="align_center">158.43</td></tr><tr><td class="align_center">13</td><td class="align_center">166.33</td></tr><tr><td class="align_center">16</td><td class="align_center">176.49</td></tr><tr><td class="align_center">19</td><td class="align_center">189.86</td></tr><tr class="table-tr"><td colspan="3"><hr class="tbody-hr"/></td></tr></table></td></tr></table>

<div>Results of conventional triaxial compression tests.</div>

Advances in Materials Science and Engineering

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Table 2

Table 2: Fractal Characteristics of Coal and Sandstone Failure under Different Unloading Confining Pressure Tests 