Optimization of Construction Parameters and Deformation Characteristics of Large-Section Loess Tunnel: A Case Study from Xi’an Metro

Loess geological tunnels are characterized by weak structure and poor self-stability of surrounding rock, so effectively controlling the excavation face distances different caverns is great significance for guiding safe construction large-section tunnels. Based on loess tunnel from Xi’an Metro Line 4, optimal distance determined based Midas numerical model. Then, surface settlement horizontal deformation analyzed monitoring data, and, finally, rationality verified. The results show that influence settlement, vault consistent. mainly occurs in range −20∼20 m centerline trough formed has asymmetric characteristics. undergo first a rapid then slow settlement. connection between initial support middle partition tensile stress bottom parts supporting compressive stress. Numerical suggest faces L1, L2, L3 which can be 9, 9 m, respectively. Construction data double-sides heading method significant effect deformation. within −17∼6 centerline. maximum 73.00% 65.50% allowable. It seen actual parameters optimized model have high reliability.