# Full-Scale Model Test of Subway Contact Channel under Mechanical Construction +
## 3 Deformation Results and Analysis  
Figure 7 shows the test results of the segment convergence deformation under the initial condition. The figure shows that each ring segment was elliptically deformed under the initial condition. The convergence deformation of the top and waist positions increased step by step with the loading step. It had a linear relationship with the number of stages and increased by about 1.5 mm under each stage of loading. After the initial condition (ten\(-\)level loading), the segment convergent deformation had a certain rebound, and the convergence deformation of the top and waist positions of each ring segment was maintained at about 15 mm (the segment was still in the elastic stage). Under the initial condition, the inward convergence deformation of the top position of each ring segment was consistent with the extrusion deformation of the waist position, indicating that the load\(-\)displacement control loading scheme could simulate the mechanical characteristics of the tunnel segment in actual soil layers. Figure 8 shows the test results of the segment convergence deformation under the adding internal support condition. The figure shows that because of the erection of the internal support system in the tunnel under the working condition, the pre\(-\)supported structure influenced the convergence deformation of the top-position segment. When the top support and the front and rear supports of the waist approached the segment and were loaded step by step, the convergence deformation of the top-position segment decreased  
Figure 6: Sketch of internal support system. by about 1 mm, and the force at the top position was 800 kN. Afterward, with the increase in the loading of the internal support, the convergence deformation of the top and waist positions of the segment was not obvious. In the later stage, when the force at the top position gradually increased to the test set point, the displacement of each ring segment was reduced by about 1\(-\)2 mm again, and the change was basically linear. Because the waist position of the middle three rings adopted the steel-ring secondary lining composite segment, the convergence deformation change of the waist position was smaller than that of the top position, indicating that the pre\(-\)supporting force at the waist position had less influence on the composite segment. Figure 9 shows the test results of the segment convergence deformation under the cutting condition. The figure shows that under the cutting condition, the change in the convergence deformation of the top position in the initial stage was small, and the change for each ring was about 1 mm. Thereafter, during the cutting process, the front and rear support forces at the waist position were kept unchanged, the thrust of the shield machine was stable at 1700 kN, and the unloading effect on the top-position support was performed within a small control range. At this time, the convergence deformation of the top-position segment increased by about 1\(-\)2 mm, but the latter remained basically stable. Because the segment at the cutting position was not constrained by longitudinal and circumferential bolts, from the time when the cutter head of the shield machine started cutting to the time when the cutter head wore the hole, a large dislocation occurred outward, and an obvious convergence deformation change occurred. Therefore, under the cutting condition, the waist position at the opening side had a significantly larger convergence deformation than that of the waist position at the back side, and the convergence deformation of the third  
Figure 8: Convergence deformations at different positions under the adding internal support condition. Figure 7: Convergence deformations at different positions under the initial condition. and fourth cutting rings was about 250 mm, indicating that the steel-ring secondary lining composite segment at the waist position was controlled by the side of the hole.