## 3 Creep Instability Mechanism of the Soft Coal Roadway
### Creep Instability Mechanism of the Roadway
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Rock Statum**} & \multicolumn{6}{c}{**Physical Mechanics Parameters of Rock Statum**} & \multicolumn{6}{c}{**Physical and Mechanical Parameters of Joint**} \\ \cline{2-13}  & **Density** & **Bulk** & **Shear** & **Friction** & **Cohesion** & **Tensile** & **Normal** & **Shear** & **Friction** & **Cohesion** & **Tensile** \\  & **(kg/m\({}^{3}\))** & **Modulus** & **Modulus** & **Angle** & **(MPa)** & **Strength** & **Stiffness** & **Stiffness** & **Angle** & **(MPa)** & **Strength** \\  & **(GPa)** & **(GPa)** & **(**c**)** & **(**c**)** & **(**MPa)** & **(GPa/m)** & **(GPa/m)** & **(**c**)** & **(**c**)** & **(**a**/**c**)** & **(**c**/**c**)** & **(**c**/**c**)** \\ \hline Medium sandstone & 2500 & 10.2 & 7.0 & 30 & 6.6 & 1.9 & 362 & 145 & 18 & 1.5 & 1.2 \\ Silestone & 2600 & 39.3 & 28.3 & 35 & 11.4 & 5.8 & 164 & 66 & 15 & 1.0 & 1.0 \\ Sandy mudstone & 2530 & 1.3 & 0.7 & 29 & 5.5 & 2.8 & 126 & 50.3 & 12 & 0.5 & 1.0 \\ Mudstone & 2520 & 2.7 & 1.6 & 28 & 5.1 & 2.6 & 89.8 & 35.9 & 12 & 0.4 & 0.8 \\ Sandy mudstone & 2580 & 45.3 & 31.2 & 33 & 9.7 & 5.2 & 167 & 66.8 & 15 & 0.1 & 1.0 \\ Sandstone & 2510 & 2.5 & 1.6 & 27 & 4.5 & 2.5 & 166 & 66 & 20 & 1.5 & 1.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Physical and mechanical parameters of rock strata and joints. Figure 8: Numerical calculation model and layout of measuring points. \(1\times 19\) prestressing strand of \(\Phi\)18.9 mm with a length of L8000 mm, boasting a breaking load of 607 kN for the anchor cable. In contrast, the shed support structure employs 36U steel. The precise parameters applied to these support structures in the experiment are detailed in Tables 5 and 6. Upon conducting simulations following the aforementioned steps and parameter settings, the displacement of the roadway over the course of excavation under the shed-cable support is graphically presented in Figure 9. From the results obtained, the following conclusions can be drawn:  
1. The deformation of the roadway exhibits significant asymmetric characteristics due to the dip angle of the strata. After implementing shed-cable support in the roadway, the first noticeable deformation occurs in the \"triangular coal\" region on the right side, specifically at the junction of the coal and rock on the right side. The subsequent deformation pattern is as follows: left side > floor > right side > roof. The maximum deformation is observed on the left side of the floor, with a heavy of 2155 mm. 2. With the increase in support time under the shed cable support, the deformation of the two sides of the roadway and the roof and floor increases, and the increase rate gradually increases, showing an obvious accelerated creep phenomenon. Through comprehensive analysis, the floor and two sides of the coal body under the original shed-cable support method have obvious unsteady creep characteristics. The support strength of the shed-cable support method is low, and the long-term rheology of the surrounding rock cannot be continuously controlled. It will even aggravate the deformation of the floor coal body, and the surrounding rock control effect is poor. As the support time increases under shed cable support, the deformation of both ribs of the roadway, as well as the roof and floor, increases. The rate of deformation increase also gradually rises, indicating the presence of accelerated creep. Comprehensive analysis reveals that the floor and ribs of the coal under the original shed-cable support method exhibit clear unsteady creep characteristics. The support strength provided by the shed-cable support method is insufficient to effectively control the long-term rheological behavior of the surrounding rock. In fact, it can even exacerbate the deformation of the floor coal and result in poor control over the surrounding rock. The above research shows that the development of meso-cracks in the soft coal surrounding the rock can reflect the creep state of coal to a certain extent.