## 3 Test Results and Theoretical Analysis
### Analysis of the Deformation Properties during Post-Peak Loading and Unloading
For the coal sample with a water content of 0.15%, the radial strain of the sample decreases from \(3.06\times 10^{-2}\) to \(2.76\times 10^{-2}\) after the first loading confining pressure, which decreases by 10.03%. After the first unloading confining pressure, the radial strain increases to \(3.42\times 10^{-2}\), which increases by 11.72%; the radial strain of the sample decreases to \(3.27\times 10^{-2}\) after the second loading confining pressure, which decreases by 4.44%. After the second unloading confining pressure, the radial strain increases to \(3.77\times 10^{-2}\), which increases by 10.06%; the radial strain of the sample decreases to \(3.61\times 10^{-2}\) after  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \(\sigma_{3}\)/MPa & \multicolumn{4}{c}{**Water Content 0\%**} & \multicolumn{4}{c}{**Water Content 0.15\%**} \\ \cline{2-10}  & \(\sigma_{1}\)/MPa & \(\sigma_{a}\)/MPa & \(\epsilon_{1}\)/\% & \(\epsilon_{3}\)/\% & \(k\)/mD & \(\sigma_{1}\)/MPa & \(\sigma_{a}\)/MPa & \(\epsilon_{1}\)/\% & \(\epsilon_{3}\)/\% & \(k\)/mD \\ \hline
3 & 13.90 & 5.58 & 2.27 & –2.37 & 0.09 & 29.99 & 10.95 & 2.23 & –3.06 & 0.023 \\
9 & 21.86 & 12.24 & 2.52 & –1.86 & 0.03 & 40.01 & 18.29 & 2.48 & –2.76 & 0.012 \\
3 & 13.41 & 5.42 & 2.77 & –2.99 & 0.10 & 28.35 & 10.40 & 2.73 & –3.42 & 0.021 \\
9 & 20.99 & 11.95 & 3.08 & –2.60 & 0.04 & 38.25 & 17.70 & 2.98 & –3.27 & 0.016 \\
3 & 12.74 & 5.20 & 3.33 & –3.43 & 0.11 & 27.04 & 9.96 & 3.23 & –3.77 & 0.028 \\
9 & 19.93 & 11.59 & 3.65 & –3.28 & 0.05 & 36.64 & 17.16 & 3.49 & –3.61 & 0.023 \\
3 & 11.80 & 4.88 & 3.89 & –3.72 & 0.14 & 25.78 & 9.54 & 3.74 & –4.01 & 0.038 \\
9 & 18.66 & 11.17 & 4.20 & –3.54 & 0.06 & 35.4 & 16.75 & 4.00 & –3.83 & 0.029 \\
3 & 11.77 & 4.87 & 4.47 & –3.99 & 0.16 & 25.34 & 9.40 & 4.24 & –4.22 & 0.051 \\ \hline \hline \multicolumn{10}{c}{**Water Content 0.32\%**} & \multicolumn{4}{c}{**Water Content 0.65\%**} \\ \cline{2-10}  & \(\sigma_{1}\)/MPa & \(\sigma_{a}\)/MPa & \(\epsilon_{1}\)/\% & \(\epsilon_{3}\)/\% & \(k\)/mD & \(\sigma_{1}\)/MPa & \(\sigma_{a}\)/MPa & \(\epsilon_{1}\)/\% & \(\epsilon_{3}\)/\% & \(k\)/mD \\ \hline
3 & 19.57 & 7.47 & 2.11 & –2.04 & 0.051 & 22.33 & 8.39 & 1.86 & –0.95 & 0.091 \\
9 & 28.61 & 14.49 & 2.36 & –1.62 & 0.028 & 31.16 & 15.34 & 2.11 & –0.63 & 0.021 \\
3 & 19.94 & 7.60 & 2.63 & –2.76 & 0.046 & 22.47 & 8.44 & 2.35 & –1.20 & 0.105 \\
9 & 28.93 & 14.59 & 2.88 & –2.32 & 0.035 & 31.50 & 15.45 & 2.60 & –0.83 & 0.025 \\
3 & 21.37 & 8.07 & 3.14 & –2.93 & 0.057 & 23.39 & 8.75 & 2.86 & –1.46 & 0.121 \\
9 & 30.45 & 15.10 & 3.39 & –2.87 & 0.039 & 32.49 & 15.78 & 3.11 & –1.07 & 0.041 \\
3 & 22.53 & 8.46 & 3.64 & –the third loading confining pressure, which decreases by 4.2%. After the third unloading confining pressure, the radial strain increases to \(4.01\times 10^{-2}\), which increases by 6.53%; the radial strain of the sample decreases to \(3.83\times 10^{-2}\) after the fourth loading confining pressure, which decreases by 4.46%. After the fourth unloading confining pressure, the radial strain increases to \(4.22\times 10^{-2}\), which increases by 5.21%. For the coal sample with a water content of 0.32%, the radial strain of the sample decreases from \(2.01\times 10^{-2}\) to \(1.62\times 10^{-2}\) after the first loading confining pressure, which decreases by 20.67%. After the first unloading confining pressure, the radial strain increases to \(2.76\times 10^{-2}\), which increases by 35.25%; the radial strain of the sample decreases to \(2.32\times 10^{-2}\) after the second loading confining pressure, which decreases by 15.53%. After the second unloading confining pressure, the radial strain increases to \(2.93\times 10^{-2}\), which increases by 6.5%. The radial strain of the sample decreases to \(2.87\times 10^{-2}\) after the third loading confining pressure, which decreases by 2.18%.