## 5 Numerical Simulation of Super-Large-Section Roadway Excavation
The low-stress area on the roof changes from a pressure-bearing status to a tensile-force-bearing status from far to near; tensile stress is generated in the part close to the roadway surface, resulting in a fracture in the roadway roof. The tensile stress upon the roadway roof increases with the increase in roadway sections, and it thereby intensifies the instability in the roof. It can be seen from Figures 11 and 12 that, when the roadway widths were 15 m, 20 m, 25 m and 30 m, the maximum deformation degrees in the roadway roof were 61.37 mm, 82.50 mm, 109.34 mm and 152.59 mm, respectively; the maximum deformation degrees in the roadway base plate were 19.89 mm, 24.74 mm, 31.08 mm and 38.17 mm, respectively; and the maximum deformation degrees in the two side walls of the roadway were 238.98 mm, 258.71 mm, 281.07 mm and 306.14 mm, respectively. As the roadway width increases, the deformation quantities in the roof, base plate and two side walls of the roadway also increase. With the roadway width increasing from 15 m to 30 m, the deformation quantities in the two side walls of the roadway increased by 28.10%, and in the roof and base plate of the roadway, they increased by 134.75%, respectively. These results show that the roadway width has a greater influence upon the deformation in both the roof and base plate than that in the two side walls of the roadway. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Name** & _h/m_ & _E/MPa_ & _\#_ & _\(\gamma\)/(g/cm\({}^{3}\))_ & _R\({}_{m}\)/MPa_ & _C/MPa_ & _\(\varphi^{c}\)_ \\ \hline mudstone & 15 & 14,000 & 0.22 & 2.54 & 1.93 & 2.49 & 37 \\ medium-grained sandstone & 1.5 & 18,200 & 0.19 & 2.59 & 2.82 & 3.58 & 38 \\ mudstone & 1 & 14,000 & 0.22 & 2.54 & 1.93 & 2.49 & 37 \\ medium-grained sandstone & 2 & 18,200 & 0.19 & 2.59 & 2.82 & 3.58 & 38 \\ mudstone & 1 & 14,000 & 0.22 & 2.54 & 1.93 & 2.49 & 37 \\ medium-grained sandstone & 3 & 18,200 & 0.19 & 2.59 & 2.82 & 3.58 & 38 \\ mudstone & 10 & 14,000 & 0.22 & 2.54 & 1.93 & 2.49 & 37 \\ coal & 2.5 & 600 & 0.29 & 1.4 & 0.52 & 2.00 & 32 \\ carbon mudstone & 1 & 16,900 & 0.26 & 2.53 & 1.26 & 2.58 & 37 \\ mudstone & 1 & 14,000 & 0.22 & 2.54 & 1.93 & 2.49 & 37 \\ sandy mudstone & 3 & 27,900 & 0.16 & 2.53 & 2.13 & 5.00 & 40 \\ medium-grained sandstone & 1.5 & 18,200 & 0.19 & 2.59 & 2.82 & 3.58 & 38 \\ mudstone & 10 & 14,000 & 0.22 & 2.54 & 1.93 & 2.49 & 37 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mechanical parameters of coal and rock. the roof and developed into surrounding rocks. When the roadway width was 30 m, the plastic zone penetrated the hard stratum in the roof and then reached the upper mud stone, causing a damage range much larger than that with a roadway width ranging from 15 m to 25 m. These results indicate that the wider the roadway, the more serious the plastic failure in the roof and the harder the corresponding control measures. Figure 12: Deformation of two sides of roadway under different roadway widths. Figure 13: Distribution map of plastic zone of roadway surrounding rock under different roadway widths. Influence of Side-Pressure Coefficient on Deformation and Failure Surrounding Rock in Rectangular Roadways with Super-Large Sections  
In order to study the influence of the side-pressure coefficient of a roadway with super-large sections upon the deformation and failure in its surrounding rocks, four groups of models were designed with their side-pressure coefficient \(\lambda\) as 0.5, 1, 1.5 and 2. The width was 20 m, the height was 20 m and buried depth was 200 m. The numerical simulation results were as follows: With different side-pressure coefficients, the perpendicular stress field cloud map concerning surrounding rock of the excavation roadway was generated, as shown in Figure 14. Furthermore, the displacement degrees were calculated, as shown in Figures 15 and 16.