Determination of the Installation Time of Secondary Liner during Excavation of Large Cross-Section Double-Arch Tunnels

Table 3

Distribution of stress release ratio in different stages.

Plan	Stress release ratio in different stages			Accumulative release ratio (%)
	Tunnel excavation	Initial support	Secondary liner
Plan 1	20	50	30	100
Plan 2	20	60	20	100
Plan 3	30	40	30	100
Plan 4	30	50	20	100