# Analysis of the Interaction Effects of Shield Structure Oblique Passing under an Existing Tunnel
## 5 Deformation Characteristics of Existing Tunnels  
### Transverse Deformation  
Figure 11 shows the lateral deformation of different sections (sections 1-1 to 5-5, locations shown in Figure 3b) during the LT excavation after the RT excavation was completed (displacement zeroing). The horizontal distance between each two sections was 9 m. Sections 2-2 and 4-4 were located directly above the LT and RT axes, respectively. After RT excavation, it was observed that the existing tunnel lining of sections 1-1, 3-3, and 4-4 deformed to an inclined horseshoe shape, with the lining of section 1-1 inclining to the left and the lining of sections 3-3 and 4-4 inclining to the right. The deformation of section 2-2 lining showed a vertical stretching horseshoe shape, while that of section 5-5 shows a horizontal stretching horseshoe shape. After RT excavation, it was observed that the existing tunnel linings of sections 1-1, 3-3, and 4-4 were deformed into an inclined horseshoe shape, with the lining of section 1-1 inclining to the left and the lining of sections 3-3 and 4-4 inclining to the right. The lining section of 2-2 was deformed into a vertically stretched horseshoe shape, and the 5-5 section lining became a horizontally stretched horseshoe shape.  
As the shield machine progressed, the transversal deformation of the existing tunnel lining in these five sections first gradually increased and then gradually converged to its original shape. When the shield tunnel face was \(-20.5\) m from the existing tunnel axis, the lining deformation of sections 4-4 and 5-5 became larger, and the lining deformation of section 5-5 was slightly larger than that of section 4-4, while the lining of section 3-3 was also slightly deformed. When the shield tunnel face was \(-4.5\) m and \(-0.5\) m away from the existing tunnel axis, the lining deformation of sections 4-4 and 5-5 was relatively obvious because the new shield tunnel was constructed with an 80\({}^{\circ}\) oblique underpass with the existing tunnel (as shown in Figure 1); thus, the lining of section 5-5 was first disturbed by the shield during the shield underpass, followed by section 4-4 and finally section 3-3. In the process of RT excavation, the cross-section lining of sections 1-1 and 2-2 was slightly deformed, and the cross-sections of sections 3-3, 4-4, and 5-5 first showed a transverse stretching horseshoe shape, after which the cross-sections inclined to the right. The deformation behavior of the cross-sections of 4-4 and 5-5 was similar to the combined 2-2 and 3-3 cross-section deformations of sections 2-2 and 3-3. Finally, it is worth noting  
Figure 11: Transverse deformation of 5 sections during RT excavation (magnification factor f = 30,000). Note: L\({}_{1}\) represents the horizontal distance of the shield palm face from the existing tunnel axis during the RT excavation, L\({}_{2}\) represents the horizontal distance of the shield palm face from the existing tunnel axis during the LT excavation after the RT excavation is completed (as shown in Figures 9 and 10).  
that after the shield tunnel penetrated the existing tunnel, the lining of the three sections gradually changed back to its original shape, while the lining of sections 1-1 and 5-5 tilted to the left and right, respectively, because the shield tunnel was able to carry out the assembly support of lining rings and synchronized grouting.