Experimental Study on Structural Form and Excavation Model of Urban Metro Cross Transfer Station with Super Large Cross Section and Shallow Excavation

Figure 9

Model test excavation process: (a) step 1: four pilot headings when excavating the main tunnel for the first time; (b) step 4: excavating core soil and rock beam of the main tunnel for the second time; (c) step 6: excavating core soil and rock beam of the main tunnel for the third time; (d) step 9: secondary lining; (e) step 10: surface injecting; (f) step 14: fourth full-face excavation of the accessorial cross tunnel.