Monitoring System for Circular Deformation in Metro Shield Tunnels in Soft Soils

Table 1

Limits of the joint opening angle.

Evaluating indicator	Joint opening inwards	Joint opening outwards
Maximum joint opening width (mm)	Δ =  = (350 – 115)θ = 235θ ≤ 6; θ ≤ 0.0255 rad	Δ =  = (350–75)θ = 275θ ≤ 6; θ ≤ 0.0218 rad
Horizontal diameter convergence (mm)	ΔD = 2342(θ1 – θ4) sin71° ≤ 31; θ1 – θ4 ≤ 0.0140 rad	ΔD = 2269(θ1 – θ4) sin67° ≤ 31; θ1 – θ4 ≤ 0.0148 rad
Bolt stress (MPa)	Δb = θ(hbt – y) = 115θσb ≤ fb = 480; θ ≤ 0.0112 rad	Δb = θ(hbb – y) = 45θσb ≤ fb = 480; θ ≤ 0.0287 rad