Table 2 Minimum safety factor for primary support shotcrete.

From: Support mechanical response analysis and surrounding rock pressure calculation method for a shallow buried super large section tunnel in weak surrounding rock

Construction step

Least safe location

Safety factor

Maximum bending moment (kN m)

Maximum axial force (kN)

3

I

7.63

122.1

− 1637.2

2

II

2.32

189.4

− 3469.1

4

III

3.93

171.4

− 3182.2

5

IV

2.39

234.7

− 5217.5

7

I

2.01

239.9

− 6210.7

Inverted arch

I

1.98

272.6

− 6311.5

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