Stability of a Rock Tunnel Passing through Talus-Like Formations: A Case Study in Southwestern China
Table 3
Configuration of dynamically adaptive support system in talus-like formations in Tayi tunnel.
Supporting system
Vd-1
Vd-2
Vd-3
Presupport
φ76 × 6 pipe shed, 9 m length, 6 m × 30 cm spacing, splicing length ≥3 m
Primary support
Mortal anchor
φ25, 60 cm × 120 cm spacing
3.5 m length
4 m length
4 m length
Steel mesh
φ8, 20 cm × 20 cm spacing
Steel arch
60 cm spacing
I 22b
I 25b
Double layer
Shotcrete
C25
28 cm
31 cm
Double layer
Foot reinforcement bolt (each side)
Upper bench: φ42 × 2, 4.5 m length
Upper bench: φ42 × 2, 5 m length
Matched to steel arch
Middle bench: φ89 × 2, 6 m length
Lower bench: φ89 × 1, 6 m length
Reversed deformation
30∼35 cm
35∼40 cm
35∼40 cm
Secondary support
Reinforced concrete
C30
50 cm
60 cm
60 cm
Reinforcement
N1: φ22@20
N1: φ22@16.67
N1: φ22@16.67
N2: φ22@20
N2: φ22@20
N2: φ22@20
N3: φ14@30
N3: φ14@30
N3: φ14@30
N4: φ8@30
N4: φ8@30
N4: φ8@30
Note: the primary support for Vd-3 is in the form of double-layer as shown in Figure 15. The unit for diameter of pipes, anchors, and steel bars is mm. The steel bars in N1, N2 and N3 are HRB 400 while the ones in N4 are HPB 300.
