Risk Analysis of Tunnel Construction Scheme Change based on Field Monitoring and Numerical Analysis

Figure 6

Construction steps of concealed excavation. (a) Excavation of middle drift (upper). (b) Excavation of middle drift (lower). (c) Construction of middle partition wall. (d) Excavation of side drift (upper). (e) Excavation of side drift (lower). (f) Construction of side drift waterproof layer and secondary lining.