## 4 Numerical Simulation of Damage Mechanism under the Original Support of II5 Rail Rise  
### Displacement Evolution Law of Roadway Surrounding Rock  
To analyze the deformation characteristics of the roadway surrounding rock, the horizontal displacement and vertical displacement of the roadway were analyzed through the displacement nephogram and measuring point data. With reference to the analysis results, twelve measuring points were set on the roadway surface to measure the displacement of the ribs, the roof, and the floor. The locations of the measuring points are given in Figure 9.  
Figure 10 shows the horizontal displacement nephograms of the roadway under the original support. After the completion of the roadway excavation (the 1 st day), the horizontal displacement was small, and the displacement of two ribs was within 2 mm. Within a short time (the 5 th day), the roadway cross-section displayed overall shrinkage, with the displacement being within 20 mm. The two ribs started to present asymmetric deformation, and the displacements of the left and right ribs were 17 mm and 13 mm,  
Figure 8: Numerical calculation model of II5 Rail Rise.  
Figure 9: Layout of displacement measuring points.  
respectively. On the 50 th day, the roadway cross-section kept shrinking overall, and the asymmetric deformation of the two ribs further expanded. The displacement of most of the left rib was 90 mm, the displacement of the bulge position at the bottom corner was up to 130 mm, and the displacement of the right rib was 70 mm. From the 50 th day to the 250 th day, the two ribs continued to deform, and the influence area of roadway deformation continued to expand. On the 250 th day, the maximum displacement of the left rib reached 410 mm, while that of the right rib reached 250 mm. On the 300 th day, the overall displacements of the left and right ribs reached 447 mm and 341 mm, respectively, displaying serious roadway section shrinkage and deformation.  
Figure 11 gives the average deformation amount and rate of the two ribs. The average deformation data of the two ribs were taken from the average values of the measured data. The displacement of the left rib was significantly greater than that of the right rib, showing asymmetric deformation. Both ribs presented obvious rheological characteristics. The deformation rate was derived from the displacement curve. The deformation rate of the left rib was significantly greater than that of the right rib. The maximum deformation rates of the left and right ribs appeared on the 18 th day: 5.5 mm/d and 5.0 mm/d, respectively. In the secondary deformation stage, the deformation rate increased in fluctuations. With the displacement rate of the left rib as an example, there were four obvious increases: on the 135 th day (1.8 mm/d), the 197 th day (2.1 mm/d), the 237 th day (2.5 mm/d), and the 300 th day (3.3 mm/d), respectively, and this displacement tended to keep rising. The time intervals of the four accelerations were 62 days, 40 days, and 63 days, respectively (average  
Figure 10: Horizontal displacement nephograms of roadway on different days. (**a**) 1 st d; (**b**) 5 th d; (**c**) 50 th d; (**d**) 200 th d; (**e**) 250 th d; (**f**) 300 th d.  
value: 55 days); the deformation accelerated by 16.7%, 19.0%, and 28.6%, respectively (average value: 21.4%). These statistics indicate that in the absence of further control measures, the deformation of the roadway surrounding rock accelerated by 21.4% every 55 days on average after it entered into the accelerated deformation stage.