## 3 Analysis of Test Data
### Analysis of Lining Stress Results
Specifically, the stress values of the arch top, left and right girdle, left and right foot of the arch, and arch bottom increase by 0.474 kPa, 0.524 kPa, 1.690 kPa, 0.803 kPa, 0.484 kPa, and 0.374 kPa, respectively. Upon the removal of the temporary support from the second ring, the initial support of the first ring assumes the majority of the pressure from the overlying peripheral rock, resulting in a significantly higher stress value. The stress values of the arch top, left and right arch waist, left and right footings, and the bottom of the arch increase by 1.210 kPa, 0.755 kPa, \(-\)0.590 kPa, 0.910 kPa, 1.210 kPa, and 0.751 kPa, respectively. The third ring's temporary support, which is distant from the initial support of the first ring, experiences minimal impact upon the removal of the first ring's initial support. The stress values show slight fluctuations, and the final stress values for the arch, left and right arch waist, left and right arch foot, and the bottom of the arch are 9.498 kPa, 6.221 kPa, 8.152 kPa, 5.120 kPa, 4.658 kPa, and 4.585 kPa, respectively. Figure 14 illustrates the time course curve of lining stress for the second set of tests. Following the excavation of the upper left 1 guide hole, the stress values for the left arch waist, left elevated arch, and upper left diaphragm wall experience an increase, reaching 9.073 kPa, 0.817 kPa, and 8.703 kPa, respectively. Notably, the stress change is most significant for the left arch waist and the upper left diaphragm wall in this construction step. Consequently, it is crucial to enhance monitoring efforts for the left arch waist and the upper left diaphragm wall during the excavation of the upper left 1 guide hole. After excavating the lower left 1 guide hole, the lower structure assumes a portion of the stress, resulting in a decrease in stress values for the upper structure and an increase in stress values for the lower structure. Stress values for the left arch waist and the left upper  
diaphrag wall decrease to 3.696 kPa and 5.353 kPa, respectively. Simultaneously, stress values for the left arch foot, left elevated arch, and left lower diaphragm wall increase to 2.812 kPa, 5.990 kPa, and 3.248 kPa, respectively. Excavating the upper right 1 guide hole induces an increase in stress values for the right arch waist, right elevation arch, and upper right diaphragm wall, reaching 6.813 kPa, 1.112 kPa, and 5.345 kPa, respectively, with minimal impact on the structure on the left side. Following the excavation of the lower right 1 guide hole, stress values for the right arch waist and the upper right diaphragm wall experience a rapid decrease to 2.952 kPa and  
Figure 14: The time-history curve of lining stress in the second group of tests. (**a**) Stress time curve of the lining of the vault and the base of the arch. (**b**) Stress time curve of arch waist lining. (**c**) Stress time-course curve of footing lining. (**d**) Stress time curve of the left diaphragm wall lining. (**e**) Stress time-curve of the right-central diaphragm wall lining. (**f**) Temporary back arch lining stress time curve. 4.433 kPa, while stress values for the right arch foot, right elevation arch, and lower right diaphragm wall increase to 2.957 kPa, 2.576 kPa, and 6.618 kPa, respectively. The stress values on the left side structure show small fluctuations. Post-excavation of the middle and upper 1 guide holes, stresses on both sides of the supporting structure increase. However, the overall stress rise is not significant due to the applied substructure. The left and right arch foot, left and right arch waist, left upper diaphragm wall, left lower diaphragm wall, right upper diaphragm wall, right lower diaphragm wall, and left and right elevation arches experience elevation, reaching 4.526 kPa, 3.821 kPa, 2.992 kPa, 3.218 kPa, 7.267 kPa, 7.931 kPa, 6.836 kPa, 8.262 kPa, 3.437 kPa, and 2.965 kPa, respectively.