Instability Mechanism of Cavity-Bearing Formation under Tunnel Excavation Disturbance

Figure 12

Stratum cavity boundary closure process. (a) Process 1. (b) Process 2. (c) Process 3. (d) Process 4. (e) Process 5. (f) Process 6.

(a)

(b)

(c)

(d)

(e)

(f)