Temporal and Spatial Effect of Surrounding Rock and Supporting Construction of a Large Soil Tunnel

Figure 2

Three-step and seven-step excavation. (a) Excavation of upper stage, (b) left of middle step, (c) right of middle step, (d) left of lower step, (e) right of lower step, (f) excavation of core soil, (g) excavation of inverted arch, (h) clamping secondary lining formwork, and (i) removal of secondary lining formwork.