## 5 Numerical Simulation of Super-Large-Section Roadway Excavation
Lastly, the plastic zones were charted, as shown in Figure 17.  
It can be seen from Figure 14 that, when the side-pressure coefficients \(\lambda\) were 0.5, 1, 1.5 and 2, the values of the maximum stress upon the two side walls were 7.76 MPa, 7.77 MPa, 7.37 MPa and 6.94 MPa, respectively, and the stress concentration coefficients were 1.55, 1.55, 1.47 and 1.39, respectively. The larger the side-pressure coefficient, the smaller the value of the maximum vertical stress upon the two side walls of the roadway, and the farther the distance between the maximum stress concentration point and the side walls of the roadway. For the roadway roof, the greater the side-pressure coefficient, the smaller the tensile stress upon its surface, and the greater the compressive stress upon its surface. When \(\lambda\) was equal to 0.5, the maximum tensile stress upon the roadway was 172.39 KPa; and when \(\lambda\) was equal to 2, the maximum tensile stress upon the roadway was 78.44 KPa. It can thus be seen that, with an increase in side-pressure coefficient, the perpendicular  
Figure 14: Stress cloud diagram of roadway surrounding rock under different lateral-pressure coefficients. The blank part is the excavated super-large section roadway. stress on both side walls of the roadway decreases as a whole, and that roadway roof is subject to both compressive stress from the overlying stratum and tensile stress from its own weight, and, therefore, is more susceptible to bed separation and fracture. It can be seen from Figures 15 and 16 that, when the side-pressure coefficients \(\lambda\) were 0.5, 1, 1.5 and 2, the maximum deformation quantities in the roadway roof were 92.64 mm, 82.50 mm, 102.43 mm and 144.94 mm, respectively; the maximum deformation quantities in the roadway base plate were 22.37 mm, 24.74 mm, 42.96 mm and 74.13 mm, respectively; and the maximum deformation quantities in the two side walls of the roadway were 169.73 mm, 258.71 mm, 471.84 mm and 801.58 mm, respectively. As the side-pressure coefficient increased, the deformation quantities in the roof, base plate and two side walls of the roadway increased accordingly; moreover, the deformation quantities in the two side walls were greater than those in the roof and base plate of the roadway. Upon the side-pressure coefficient increasing from 0.5 to 2, the deformation quantities in the two side walls of the roadway increased by 90.48%, and those in the roof and base plate of the roadway increased by 372.27%, respectively. The increasing range of deformation quantities in both the roof and base plate was much greater than that of deformation quantities in the two side walls. In this regard, synergistic support by an anchor bolt/cable whose elongation can adapt to large deformation without failure can be employed to restrict roof deformation in a roadway with super-large sections so as to avoid roof caving. Figure 16: Deformation of two sides of roadway under different lateral-pressure coefficients. Figure 15: Deformation of roadway roof and floor under different lateral-pressure coefficients. It can be seen from Figure 17 that when the side-pressure coefficients \(\lambda\) were 0.5, 1, 1.5 and 2, the maximum ranges of the plastic zone were 19.5 m, 8.5 m, 11.5 m and 15 m, respectively; the widths of the plastic zone on the roadway side walls were 1.5 m, 1.5 m, 2 m and 2.5 m, respectively. When the side-pressure coefficient increased from 0.5 to 1, the plastic zone changed from a \"butterfly-like\" shape to an \"oval\" shape; when the side-pressure coefficient increased from 1 to 2, the plastic zone gradually changed from an \"oval\" shape to a \"butterfly-like\" shape. With the increase in side-pressure coefficient, the tensile and shear failure zones on the two side walls of the roadway increased.