Submarine Fender System Applied to Underwater Structures in Offshore and Port Projects

Submarine Fender System Applied to Underwater Structures in Offshore and Port Projects

1. Project Background

With the rapid development of offshore engineering, sea-crossing bridges, and port infrastructure, underwater structures are increasingly exposed to collision risks from construction vessels, tugboats, and floating equipment. Conventional fender systems are mainly designed for above-water or quay applications and are not suitable for long-term underwater protection.

To address this challenge, a Submarine Fender system was adopted in an offshore project to protect underwater steel piles and concrete pile caps, effectively reducing collision damage between vessels and underwater structures.

2. Project Overview

Project Name: Offshore Underwater Structure Collision Protection Project

Location: Eastern coastal area of China

Protected Structures: Underwater steel pipe piles and concrete pile caps

Design Water Depth: -6 m to -15 m

Main Risks: Vessel deviation during construction, accidental tugboat impact, floating structure movement

3. Solution Design

3.1 Fender Type Selection

Based on water depth, environmental conditions, and collision energy analysis, high-elasticity rubber Submarine Fenders were selected, featuring:

High energy absorption capacity

Low reaction force to minimize structural stress

Excellent resistance to seawater and aging

Suitable for long-term underwater operation with low maintenance requirements

3.2 Layout Arrangement

Submarine Fenders installed circumferentially around underwater piles

Modular design adopted for ease of underwater installation

Fixed to the main structure using stainless steel chains and brackets

Optimized spacing to ensure full protection while minimizing flow interference

3.3 Design Parameters (Typical)

Energy absorption per fender: 120–200 kJ

Design compression ratio: ≤ 50%

Design service life: ≥ 15 years

4. Installation and Construction

4.1 Installation Method

Installation carried out by divers with underwater lifting support

Pre-installation inspection completed onshore

Accurate underwater positioning followed by fixation and tensioning

4.2 Challenges and Mitigation Measures

Challenge Mitigation Measure

Low underwater visibility Use of underwater markers and sonar assistance

Tidal current influence Installation scheduled during slack tide

High positioning accuracy requirement Modular design to reduce on-site adjustment

5. Performance Evaluation

Since commissioning, the Submarine Fender system has demonstrated excellent performance:

Successfully absorbed multiple minor vessel impacts during construction

No visible damage observed on underwater structures

Fender units remain intact without cracking or detachment

Significantly reduced maintenance costs and downtime risks

6. Project Value and Key Takeaways

6.1 Project Value

Enhanced safety and durability of underwater structures

Reduced economic losses caused by accidental collisions

Provided a replicable reference for similar offshore projects

6.2 Key Takeaways

Accurate collision energy assessment is critical for proper fender selection

Submarine Fenders are well-suited for long-term underwater protection

Proper installation design significantly reduces construction risks

7. Conclusion

As a professional underwater collision protection solution, Submarine Fender systems offer clear advantages for offshore engineering and port underwater structures. This case study demonstrates that, with proper design and installation, Submarine Fenders can effectively improve structural safety and reliability, showing strong potential for wider application.