## 3 Analysis of Test Data
### Analysis of Lining Stress Results
Upon the excavation of the middle and lower 1 guideway, stress within the tunnel concentrates downward, resulting in a decrease in superstructure stress and an increase in substructure stress. The stress values for the upper left diaphragm wall, upper right diaphragm wall, left elevation arch, and right elevation arch decrease to 5.169 kPa, 5.576 kPa, 1.471 kPa, and 1.451 kPa, respectively. Meanwhile, the stress values for the left arch waist, right arch waist, left arch foot, right arch foot, lower left diaphragm wall, lower right diaphragm wall, and arch bottom increase to 5.606 kPa, 5.001 kPa, 3.915 kPa, 3.605 kPa, 9.244 kPa, 10.386 kPa, and 4.683 kPa. The excavation of the left section of the second ring tunnel predominantly affects the support structure on the left side. The stress values for the left arch waist, left arch foot, left upper diaphragm wall, left lower diaphragm wall, and left superelevation arch increase to 5.954 kPa, 4.596 kPa, 8.194 kPa, 9.380 kPa, and 5.766 kPa, respectively, while the stress value on the right side of the support structure undergoes minimal change. Subsequently, the excavation of the right section also elevates the stress value of the right supporting structure. The stress values for the right arch waist, right arch foot, right upper diaphragm wall, and right superelevation arch increase to 5.047 kPa, 5.078 kPa, 6.988 kPa, 9.170 kPa, and 4.932 kPa, respectively. The stress is concentrated again on the substructure after the completion of the intermediate section excavation. The stress pattern of the support structure during the excavation of the third ring section follows the same trend as the second ring, albeit with a lesser degree of influence. Upon completing all guide hole excavations, the stress magnitude for each structure matches that of the first group. The highest to lowest stress values are the lower diaphragm wall, upper diaphragm wall, arch waist, arch bottom, arch foot, and superelevation arch, respectively. The stress change after removing the temporary support follows the same rule as the first group, resulting in an elevated stress value for the initial support. The final stress values for the left and right arch waist, left and right arch foot, and arch base are 7.741 kPa, 8.812 kPa, 5.934 kPa, 5.233 kPa, and 7.464 kPa, respectively. Compared with the first set of tests, the second set was conducted after excavating the upper guide tunnel on one side, allowing subsequent excavation of the lower guide tunnel on the same side. This enabled the substructure to share some of the stresses, resulting in a more evenly distributed overall structural stress. In the first group of tests, the average stress values for the left arch waist and left upper diaphragm wall during the excavation of the first ring tunnel were 5.621 kPa and 7.018 kPa, respectively. In the second group of tests, these values decreased to 4.487 kPa and 5.621 kPa, respectively, representing a 20.17% and 19.91% reduction compared to the first group. Excavating the right (left) side guide tunnel followed by the excavation of the lower guide tunnel in both groups resulted in the connection of the upper and lower structures, forming a closed loop and increasing overall stability. Construction disturbance had minimal impact on the entire structure. In the first group, after excavating the upper-left 1 guide hole and applying the supporting structure, the construction of the upper-right 1 guide hole reduced the stress value of the left arch waist from 7.174 kPa to 6.073 kPa, with a strain change of 1.101 kPa. In the second group, after the construction of the lower-left 1 guide hole, the construction of the upper-right 1 guide hole and the lower-right 1 guide hole reduced the stress value of the left arch waist from 3.696 kPa to 3.550 kPa, and then increased to 3.914 kPa, with an average stress change of 0.255 kPa.