Support Measures to Prevent the Deformation and Failure of a Carbonaceous Mudstone Tunnel

Figure 18

The strain of steel arch of three test sections: (a) after the upper step excavation (unit: με); (b) after the middle step excavation (unit: με); (c) after the lower step excavation (unit: με); (d) after stabilization (unit: με).

(a)

(b)

(c)

(d)