## 3 Analysis of Results
### Factors Influencing the Roadway Zonal Disintegration  
#### 3.3.1 Effect of the Surrounding Rock Strength  
Based on the parameter settings depicted in Figure 6, new simulation schemes were designed by varying the surrounding rocks' internal friction angle, the cohesive force, and the uniaxial tensile strength, respectively, as shown in Table 3. In schemes 1-3, both the initial and residual values of the internal friction angle, cohesive force, and uniaxial tensile strength were doubled, respectively. In schemes 4-6, the above parameters were reduced by \(1/3\), respectively. The remaining physical and mechanical parameters in all schemes, such as density and bulk modulus, remained unchanged.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Scheme No.**} & \multicolumn{3}{c}{**Initial Strength**} & \multicolumn{3}{c}{**Residual Strength**} \\ \cline{2-7}  & **Internal Friction** & **Cohesive Force,** & **Tensile Strength,** & **Internal Friction** & **Cohesive Force,** & **Tensile Strength,** \\  & **angle,**\({}^{\circ}\) & **MPa** & **MPa** & **Angle,**\({}^{\circ}\) & **MPa** & **MPa** \\ \hline
1 & 36 & 3 & 2.4 & 24 & 1 & 0.8 \\
2 & 18 & 6 & 2.4 & 12 & 2 & 0.8 \\
3 & 18 & 3 & 4.8 & 12 & 1 & 1.6 \\
4 & 18 & 2 & 2.4 & 12 & 0.8 & 0.8 \\
5 & 12 & 3 & 2.4 & 9 & 1 & 0.8 \\
6 & 18 & 3 & 1.6 & 12 & 1 & 0.5 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Strength parameters of rock mass in the designed schemes.  
Figure 13: Fracture state of roadway-surrounding rock in [26]: (**a**) physical image; and (**b**) shear stress.  
Figure 14 shows the distribution pattern of the significantly fractured zones in the roadway-surrounding rocks for the strength parameters in schemes 1-6. As seen in Figure 14, the increased rock strength parameters hindered the development of the disintegration zones and vice versa. After the internal friction angle was doubled, significant fractured zones developed only on both sides (see Figure 14a), and the maximum shear strain increment of 0.06 appeared at two footings, reaching about 29% of the value in the original scheme (see Figure 7e). After the cohesive force was doubled, significantly fractured zones also developed on two sides (Figure 14b). The maximum shear strain increment appeared on two shoulders and footings and approximately equaled 0.105, which was 50% of the original scheme's value. After the tensile strength was doubled, the distribution pattern and range of the fractured zones (see Figure 14c) were similar to those in the original scheme, while the maximum shear strain increment remained unchanged (0.21). Therefore, the effect of tensile strength on the development of fractured zones was weaker than that of the internal friction angle and cohesive force.  
When the original scheme's values of the internal frictional angle and tensile strength were reduced by 2/3, the distribution pattern of significant fractured zones showed a slight difference (see Figure 14e,f). Nevertheless, the maximum fracturing depths in the surrounding rocks increased by approximately 52 and 39%, respectively. The maximum shear strain increments increased by approximately 43 and 64% compared to the original scheme's values. After the cohesive force was reduced by 2/3, the fracture planes pointed toward deeper parts of the surrounding rocks appeared at the angular points of the second layer of the fracture loop and the first/second layer intersection points of the fracture loop in the conjugate fracture plane direction (see Figure 14d). The maximum depth for the fractured zone was doubled, and the maximum shear strain increment increased by 107% compared to the original scheme's value (see Figure 6e). Conclusively, the cohesive force imposed the most significant effect on the degree of zonal disintegration.