Application of the Upper-Bench CD Method in Super Large-Span and Shallow Tunnel: A Case Study of Letuan Tunnel

Table 5

Maximum internal force of initial support.

Construction method	Axial force		Bending moment
	Maximum (kN)	Position	Maximum (kN·m)	Position
Upper-bench CD method	2000	Right side of vault	105	Right arch foot
CD method	2180	Right arch waist	162	Right foot
CRD method	1970	Left arch foot	69	Left foot
Both-side drift method	1700	Right arch waist	143	Left foot
Field test	1967	Left arch foot	11.7	Left foot