Instability Process of Crack Propagation and Tunnel Failure Affected by Cross-Sectional Geometry of an Underground Tunnel

Figure 11

The strain in the surrounding rock mass during loading. (a) Ring strain at initial load. (b) Radial strain at initial load. (c) Ring strain at maximum load. (d) Radial strain at maximum load.

(a)

(b)

(c)

(d)