Project Overview

Xiaolangdi Sand Drainage Tunnel is the first hydraulic tunnel in my country that uses unbonded prestressed concrete lining. Since it was put into use in 1999, after years of operation, it has been found that some anchorage slot construction joints have oil and water seepage. The analysis believes that these greases come from the protective grease in the prestressed ring anchor strand. Due to the long-term operation of the sand discharge tunnel at a high water level, the long-term oil and water seepage of the anchor groove will directly affect the durability of the steel strand and endanger the safe use of the sand drainage tunnel.

Overall treatment plan

Adopt chemical grouting inside the construction joints, and apply a comprehensive treatment plan of CFRP reinforcement and anti-seepage on the surface.

Carbon fiber reinforced construction process

(1) Base surface treatment: polish the construction surface with a polisher and clean it with a blower;

(2) Leveling of the base surface: apply epoxy glue to the unevenness of the surface pits to achieve smoothness;

(3) Primer coating: When the leveling material is fully cured and has a certain strength, the primer should be evenly painted on the base surface according to the size of the carbon fiber fabric attached;

(4) Paste carbon fiber fabric

1) Cut carbon fiber fabric according to the size and quantity of design requirements;

2) The lap length of carbon fiber fabric should not be less than 20cm;

3) Paste the carbon fiber fabric, apply impregnating glue, roll repeatedly with a roller to remove air bubbles, and make the impregnating glue fully soak the carbon fiber fabric.

Process result

Anchor grooves of the sand discharge tunnel have processed 1254 anchor grooves, and are reinforced with carbon fiber for about 2,000 square meters. The chemical grouting inside the anchor groove eliminates the oil and water leakage of the anchor groove.The CFRP reinforcement effectively solves the defect that the first and second phases of the anchor groove cannot be jointly stressed. After treatment, it has been tested for many years and has been in good condition.