Research on Construction Methods for Ultralarge Y-Shaped Tunnel Sections

Table 1

Technical specifications for supporting parameters of partial sections of the Liantang large-span bifurcated tunnel.

Lining type	Large-span section A	Main line of multiarch section	Connecting RO line at Liantang port in multiarch section
Anchor setting	RM28 prestressed anchor; L = 8.0 m; spacing 0.7 × 1.0 m	φ25 cartridge bolt; L = 3.5 m, spacing 1.0 × 1.0 m	φ25 cartridge bolt, L = 3.5 m, spacing 1.0 × 1.0 m
Initial support	C30 shotcrete, thickness 35 cm; φ8 steel mesh, spacing 20 × 20 cm; I25b steel arch frame; spacing 70 cm	C30 shotcrete, thickness 22 cm; φ8 steel mesh, spacing 20 × 20 cm; I16 steel arch frame, spacing 100 cm	C30 shotcrete, thickness 22 cm; φ8 steel mesh, spacing 20 × 20 cm; I16 steel arch frame, spacing 100 cm
Secondary lining	C35 reinforced concrete; thickness 70 cm	C35 reinforced concrete; thickness 45 cm	C35 reinforced concrete; thickness 40 cm