## 3 Numerical Simulation Analysis of Deformation Mechanism of Tunnel-Landslide Orthogonal System
### Early Warning Model of Tunnel-Landslide Orthogonal System Based on Newtonian Force Variation  
Based on the numerical simulation analysis of the tunnel-landslide orthogonal system and the Newtonian force disaster warning model of landslide proposed by the Academician [PERSON], three Newtonian force monitoring and warning models of the tunnel-landslide orthogonal system were established. They are the overall stability model, slope crack model, and tunnel damage model, which systematically describe the Newtonian force characteristics during the whole process of geologic hazards in the tunnel-landslide orthogonal system.  
1. Overall stabilization mode: As shown in Figure 24a, the Newtonian force monitoring curve keeps a constant value of the vertical coordinate, and the slope is 0, which is approximated as a horizontal straight line. At this stage, the slope and the tunnel maintain a relatively stable state, and the whole tunnel-landslide orthogonal system is in a stable state. 2. Slope crack mode: As shown in Figure 24b,c, the Newtonian force monitoring curve shows an increasing trend with the development of time or an instantaneous surge, and the slope of the monitoring curve is greater than 0, showing a sudden increase or jump phenomenon. At this stage, continuous cracks are generated on the slope surface, and the tunnel behaves in a relatively stable state. The larger the increasing slope or jumping variable is, the larger the slope cracks are and the larger the landslide thrust on the tunnel is, and the tunnel structure will experience tension bending or shear damage, resulting in cracking of the second lining, through cracks at the top, slagging, and other phenomena, and the whole tunnel-landslide orthogonal system enters into a relatively unstable state.  
Figure 24: Newton force monitoring and early warning model of tunnel–landslide orthogonal system. (**a**) Overall stabilization mode, (**b**) Slope crack mode1, (**c**) Slope crack mode2, (**d**) Tunnel failure mode.  
3. Tunnel failure mode: As shown in Figure 24d, the Newtonian force grows in a short period and there is a sudden drop. The Newtonian force monitoring curve slope from the more than 0 growth stage suddenly changes to the less than 0 decline stage, indicating that the slope surface cracks have been developed through to the interior of the slide body, with the formation of a complete sliding surface. At this stage, the landslide occurs to a greater extent, the slope will appear with large cracks and large fractures, and the tunnel by the landslide thrust exceeds the critical maximum value. There will be a greater degree of tensile bending and shear damage, and the tunnel, if located in the interior of the landslide body section of the vault, may present larger deformation or even collapse. If the tunnel is located in the external section of the landslide, circular cracks will appear at the end of the tunnel, and in serious cases, even transverse shear faults in the direction of landslide movement will occur. [PERSON]'s force monitors the curve slope, the positive and negative turning point, which is the tunnel-landslide orthogonal system near the slip damage warning point.