Blog

Steel Sheet Pile Cofferdam Construction: Key Procedures and Best Practices

1. Construction Preparation

① Inspection and Classification

  • Transport new and used steel sheet piles to the site.

  • Conduct detailed inspections, measurements, and classification, labeling each pile accordingly.

② Repair and Modification

  • Straighten bent, damaged, or improperly locked sheet piles using cold bending, hot forging, welding, or cutting.

  • For insufficient lengths, weld additional sections of the same type—first butt welding, then reinforcing with steel plates.

2. Installation of Steel Sheet Pile Cofferdam

① Guide Frame Setup

  • Precisely measure and drive two sheet piles, then weld steel brackets.

  • Place two additional sheet piles on the brackets to form a stable guide frame (removed and reinstalled after completion).

② Pile Driving

Equipment:

  • 10-ton floating crane

  • 60T hydraulic vibratory pile hammer

  • Transport barge (modified from three standard barges)

  • 40T crawler crane

Driving Method:

  • Install three sides of the rectangular cofferdam first, then the final side after alignment.

  • Advantages: Faster installation, minimal alignment errors, and easier closure.

Driving Sequence:

  • Start upstream, then proceed downstream for closure.

Verticality Control:

  • Two workers monitor alignment using plumb lines from 50–100 meters away.

3. Cofferdam Sealing

① Dredging

  • After closure, remove sediment using divers and high-pressure water jets.

  • A slurry pump extracts loosened mud from the basin.

② Rock Filling and Concrete Sealing

  • After reaching design elevation, fill with 50 cm of crushed stone (max. 20 cm diameter).

  • Pour a 1.5 m thick underwater C25 concrete seal in one continuous operation using tremie pipes (3.0 m effective radius).

4. Installation of Internal Bracing

① Setup After Sealing

  • Begin dewatering and install wales and bracing once concrete reaches 50% strength.

② Key Principles:

  • “Brace first, dewater later”—install supports layer by layer during dewatering.

  • First, dewatering is critical; ensure sufficient pumps for rapid water removal.

  • Reinforce corners with steel sections due to complex stress distribution.

③ Monitoring

  • Focus on deformations in wales, bracing, and sheet piles.

  • If excessive movement occurs, halt dewatering, refill the cofferdam, and reinforce before resuming.

Case Study: Main Pier Foundation Construction

Project Overview:

  • Design: 16 × φ250 cm piles, 52 m deep.

  • Challenge: Steep riverbed with 12 m water depth variation.

Innovative Solutions:

  • Modified double-wall steel cofferdam with rectangular, asymmetrical high-low cutting edges.

  • Installed using a guide frame barge.

  • Step-like concrete pouring with partition plates to reduce material usage.

Construction Steps:

  1. Fabricate a cofferdam on-site.

  2. Install using guide barges.

  3. Stabilize and set steel casings.

  4. Form a drilling platform for pile construction.

  5. After pile testing, dewater, trim piles, and build the cap.

 

Recent Posts