Study on Energy Release of Surrounding Rock under the Multiple Unloading Disturbance during Tunnel Excavation

Figure 9

Energy release process of surrounding rock on the right side of the excavation section. (a) Rock mass unit at 0.2 m away from the excavation boundary. (b) Rock mass unit at 1.2 m away from the excavation boundary. (c) Rock mass unit at 2.2 m away from the excavation boundary. (d) Rock mass unit at 3.2 m away from the excavation boundary.

(a)

(b)

(c)

(d)