## 3 Numerical Simulation Analysis of Deformation Mechanism of Tunnel-Landslide Orthogonal System
### NPR Constant-Resistance Large Deformation Anchor Cable Axial Force Analysis  
The NPR constant-resistance large deformation anchor cable axial force changes under the upper landslide thrust in this tunnel-landslide orthogonal system are investigated using the discount scheme in Section 3.4. In the following, the changes in axial force of the NPR constant-resistance large deformation anchor cable under five different discount schemes are analyzed. The NPR constant-resistance large deformation anchor cable axial force analysis is carried out under the original plan (Plan 1) without reducing the shear strength parameter of the geotechnical body, and the stability analysis under the original plan in Section 3.5 shows that the tunnel-landslide orthogonal system at this time maintains a stable state. As shown in Figure 21, the axial force value of the NPR constant-resistance large deformation anchor cable initially maintains a relatively stable state under the prestressing condition with the increase in calculation steps, and then the axial force value slowly and slightly decreases to reach a stable state. The main reason is that the initial prestress of the preset NPR constant-resistance large deformation anchor cable is high, and the geotechnical body is gradually extruded to initiate slow creep deformation and a certain amount of stress relaxation occurs, which ultimately makes the axial force value of the anchor cable drop slowly and then maintain a certain constant-resistance value. At this stage, the anchor cable axial force value does not show any sudden increase or decrease, which also verifies that the tunnel-landslide orthogonal system remained relatively stable under the original scheme. The shear strength parameters of the geotechnical body under the discounting conditions of Scheme II and III were taken to analyze the axial force of the NPR constant-resistance large deformation anchor cable, respectively. With the increase in the discount factor, as shown in Figure 22a,b with the increase in the calculation steps, the NPR constant-resistance large deformation anchor cable axial force has a sudden drop, and then increases  
Figure 21: Monitoring the axial force of the anchor cable under the original scheme. Figure 20: NPR constant-resistance large deformation anchor cable initial prestress. and gradually reaches a stable state. From Section 3.6, it can be seen that at this time, small-scale landslides occur on the slope, and the tunnel settles as a whole, and at this time, the pre-added stress of the NPR constant-resistance large deformation anchor cable is released rapidly, resulting in a sudden drop in the axial force of the anchor cable. As the landslide gradually stops and reaches stability, the tunnel-landslide orthogonal system enters a new stable state, and the NPR constant-resistance large deformation anchor cable is re-tightened and maintains a certain unchanged constant-resistance value. The shear strength parameters of the rock and soil bodies under the discounted conditions of Scenarios 4 and 5 were taken to analyze the axial force of the NPR constant-resistance large deformation anchor cable, respectively. These two schemes' discounting parameters are larger, as can be seen from Section 3.6. At this time, the slope produces a larger-scale landslide, driving the tunnel as a whole to move along the landslide direction. As shown in Figure 23a,b, with the increase in calculation steps, the axial force of the NPR constant-resistance large deformation anchor cable has a sudden drop, and the maximum value of the sudden drop reaches nearly 200 kN. As the calculation continues, the landslide gradually reaches a new stable state, and the NPR constant-resistance large deformation anchor cable is re-tightened under the action of constant resistance and continues to maintain a certain value of constant resistance, and the axial force remains stable. Figure 23: Monitoring the axial force of the anchor cable under the conditions of schemes 4 and 5. (**a**) Plan 4, (**b**) Plan 5.