FRP Pile Jakcets

A certain cross sea bridge has been in service for over 15 years, and with the increase of its service life, the underwater concrete ocean piles of the bridge are facing many serious problems.

Due to long-term exposure to chemical erosion from seawater, repeated erosion from tides and waves, as well as damage to marine organisms, it has been found during regular underwater inspections that a large number of pile foundations have experienced concrete protective layer peeling off, exposed steel bars rusting, and other conditions, seriously affecting the safety and durability of bridge structures and posing a potential threat to the safety of passing vehicles and pedestrians.

After expert evaluation, it has been decided to use fiber-reinforced polymer (FRP) pile sleeves for significant structural repair and reinforcement of these damaged underwater concrete marine piles.

Fiber Reinforced Polymer (FRP) pile jacks

Considering the harsh nature of the marine environment, the engineering team has decided to use Fiber Reinforced Polymer (FRP) pile jacks for repair and reinforcement. FRP materials are composed of fiber-reinforced materials and matrix resins, and have the following advantages:

• Excellent corrosion resistance: It can effectively resist the chemical erosion of seawater and avoid corrosion problems like traditional steel reinforcement.

• High strength to weight ratio: FRP materials have high strength but relatively light weight, which increases the bearing capacity of pile foundations without generating excessive additional loads on them.

• Good designability: It can be flexibly cut and shaped according to the shape and reinforcement requirements of the pile foundation, meeting different reinforcement requirements.

Construction process

Preparation in advance: Use professional underwater testing equipment such as underwater cameras, ultrasonic flaw detectors, etc. to conduct a detailed investigation of the degree of damage to each damaged pile foundation, determine the location of damage, concrete spalling area, steel corrosion, etc., and provide accurate data for the subsequent customization of FRP pile sleeves. At the same time, the construction area should be delineated, underwater obstacles should be cleared to ensure safe and orderly construction.

Pile foundation surface treatment: With the help of underwater robots equipped with high-pressure water guns, a comprehensive cleaning of the pile foundation surface is carried out to remove loose concrete fragments, marine biological attachments, and rust layers on the steel reinforcement surface, making the pile foundation surface reach a solid and clean state, creating good conditions for subsequent bonding work.

FRP pile sleeve installation: Transport the customized FRP pile sleeve to the construction site and use underwater lifting equipment to accurately lift it to the corresponding pile foundation position. Apply underwater special adhesive evenly on the surface of the pile sleeve and pile foundation, and then slowly and accurately place the FRP pile sleeve on the pile foundation with the help of underwater operators and special tools, ensuring a tight fit between the pile sleeve and the pile foundation, and eliminating air and excess adhesive between the two. Afterwards, use a fastening device to temporarily fix the pile sleeve and wait for the adhesive to solidify.

Sealing and protection treatment: After the adhesive is cured, the joints of the FRP pile sleeve are sealed and filled with waterproof sealant to prevent seawater from seeping into the gap between the pile sleeve and the pile foundation. At the same time, apply a layer of anti fouling coating on the surface of the pile sleeve to reduce the adhesion of marine organisms

FRP pile sleeves have been used for significant structural repair and reinforcement of underwater concrete marine piles, successfully solving the problem of diseases caused by pile genetic erosion in the marine environment, and providing reliable guarantees for the safe operation of bridges.