Structural Safety Assessment of Existing Multiarch Tunnel: A Case Study

Table 6

Major restoration programme for structural defects of Shitigou tunnel.

Type of defects		Restoration programme
Liner crack		A V-shaped groove 5 cm wide and 3 cm deep was made following the direction of crack, a hole every 0.5 m at the junction of the groove edges was bored, and cement-water glass grout or epoxy resin grout was infused at pressure of 0.15–0.2 MPa.
Tunnel seepage	Side wall	A small groove along the watered points was made and led to the permanent drainage system. The size of the small groove section was 5 × 5 cm. The surroundings of the small groove were smooth, half PVC of 50 mm was reversed into the small groove, and plugging agent or epoxy resin mortar was used to fill in the small groove.
	Arch	Grouting holes with spacing of 1-2 m and diameter of 42 mm were made, and then the grouting pipe was laid. For the little water leakage, plugging agent or epoxy resin mortar could be infused using a small grouter with the grouting pressure of 0.2–0.4 MPa. For the great water leakage, chemical grouting shall be employed.
Liner void		The cement paste mixed liquor was used in grouting, consisting of 80% cement, 20% grade-II coal ash, and aluminum powder expansive agent mixed with 1/10000 cement. The grouting pressure shall be controlled within 0.3–0.5 MPa.