Ground Settlements due to Construction of Triplet Tunnels with Different Construction Arrangements

Table 1

PLAXIS 2D construction phases (Schotte et al. [24]).

No.	Phase	Action	Applied pressure (MPa)	Pressure increment (MPa/m)
0	Initial	—	—	—
1	Face pressure, σf	(i) Deactivate soil cluster		0.012
		(ii) Apply face pressure
2	TBM	(i) Remove face pressure	—	—
		(ii) Apply TBM
3	Tail pressure 0, σt0	(i) Remove TBM		0.016
		(ii) Apply tail pressure 0
4	Tail pressure 1, σt1	(i) Apply tail pressure 1		0.011
5	Tail pressure 2, σt2	(i) Apply tail pressure 2		0.011
6	Final state	(i) Remove tail pressure 2	—	—
		(ii) Activate tunnel lining

U, pore water pressure; σ_a, active earth pressure.