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Maximising Berth Depth for Larger Vessels
As global trade grows, the need for ports to accommodate larger vessels with deeper drafts has become increasingly urgent. Expanding and optimising port infrastructure, especially deepening existing berths, is essential for remaining competitive in the international shipping industry. However, this process is not without its challenges. Ports must find effective, sustainable methods to deepen berths while maintaining structural integrity and minimising environmental disruption.
In situ concrete mattresses have emerged as an innovative and practical solution. This technology not only stabilises the seabed but also enables efficient excavation, allowing port berths to be deepened cost-effectively. For port owners and infrastructure managers, in situ concrete mattresses offer an advanced method for future-proofing their facilities and ensuring that their ports can handle the demands of modern shipping.
The Growing Need for Deepening Port Berths
The maritime industry has witnessed a significant increase in the size of vessels, particularly container ships and tankers. Modern vessels require deeper berths to accommodate their drafts, and ports that cannot meet these requirements risk losing business to competitors. Deepening port berths is a complex engineering challenge. Excavating the seabed must be done carefully to avoid destabilising existing structures like quay walls, which could lead to costly damage or dangerous failures.
Before & After Concrete Mattress Installation
In many cases, existing ports were not originally designed with the future in mind, so upgrading them to meet current demands is essential. This is where in situ concrete mattresses play a crucial role. Their ability to stabilise and protect the seabed during excavation allows ports to increase their berth depth without compromising the structural integrity of adjacent infrastructure.
What Are In Situ Concrete Mattresses?
In situ concrete mattresses are constructed using fabric formwork placed directly on the seabed. The concrete is poured into the formwork, which shapes and contains it as it cures, creating a durable and stable surface that conforms precisely to the seabed’s natural contours. This tailored approach ensures maximum stability and protection, allowing the installation to adapt seamlessly to the unique conditions of each port’s environment.
The concrete mattress acts as a protective barrier, reinforcing the seabed and preventing erosion caused by tidal currents, vessel propellers, and other dynamic marine forces. This stabilising effect is critical for ensuring the long-term safety and functionality of port infrastructure.
How In Situ Concrete Mattresses Facilitate Berth Deepening
When deepening a port berth, one of the primary concerns is the stability of the quay wall. Excavating material from the seabed can undermine the foundations of these structures, leading to potential settlement or collapse if not properly managed. In situ concrete mattresses provide a reliable solution by reinforcing the seabed before excavation, ensuring that the quay wall remains stable throughout the process.
The key benefits of in situ concrete mattresses in port deepening projects include:
Withstanding High Propeller Forces
In situ concrete mattresses are specifically designed to endure the powerful hydrodynamic forces generated by propeller wash and tidal flows. These mattresses are ideal for ports handling large vessels, where unprotected seabeds can suffer significant erosion or damage. The concrete mattresses distribute these forces evenly across the seabed, providing a stable and durable layer of protection.
Thin but Strong Protection
A major advantage of in situ concrete mattresses is their ability to provide effective protection with the lowest relative thickness compared to other methods like rock armour. This thin yet strong layer maximises available water depth, allowing for deeper vessel drafts without requiring extensive material or space. The slim design makes it easier for ports to deepen their berths while maintaining full protection for the quay wall and seabed.
Cost-Effective Solution
Compared to traditional methods like rock armour, in situ concrete mattresses are more affordable. They require fewer materials and less labour during installation, reducing costs. This cost-effectiveness makes them an attractive option for port owners looking to optimise their berths without exceeding budgets. Their durability also reduces long-term maintenance costs, adding to their financial benefits.
Case Study: Port of Szczecin
A prime example of the successful use of in situ concrete mattresses can be seen in the project at the Port of Szczecin. The installation of 11,000m² of concrete mattress scour protection carried out by contractor Aarsleff to deepen the 250-metre grain quay. This project aims to enable larger vessels to dock without compromising the stability of the quay wall, a key challenge for many ports.
To achieve this, the berth pocket has been dredged to its maximum depth with a precise dredging tolerance of just 100mm. Specialised measures, such as ground anchors in selected locations, have been implemented to maintain the structural integrity of the quay wall during the process.
One of the standout aspects of this project is the custom-made formwork, produced offsite to meet specific requirements. The formwork is rolled out onto the seabed, secured in place, and filled with concrete from the quayside. Divers assist by moving the filling hose between designated filler points, ensuring even concrete distribution across the mattress panels. A total of 71 panels, each averaging 185m², will be installed, with each panel requiring 41m³ of concrete. Given the installation pace, 82m³ of concrete is filled per day, with each filling process taking around six hours. The work is carefully managed to minimise disruption to port operations, pausing as needed to allow vessels to move in and out.
This project demonstrates how in situ concrete mattresses provide robust and durable scour protection while allowing ports to deepen their berths and safeguard their infrastructure from the forces generated by tidal currents and vessel movements.
Ensuring Long-Term Protection and Durability
A key aspect of in situ concrete mattress design is its ability to offer long-term scour protection. At the Port of Szczecin, Hinged Edge (HE) blocks have been incorporated into the concrete mattress installation. These 4-tonne blocks are tied into the main concrete apron and designed to drop independently in the event of scouring, providing an additional layer of protection. This edge protection ensures the concrete apron remains intact, preventing it from being undermined by tidal flows or vessel movements.
By combining HE blocks with the concrete mattress, the port is ensuring long-term durability and protection against high-pressure conditions caused by propeller action and tidal forces. This approach minimises future maintenance requirements and protects port infrastructure well into the future.
Conclusion
In situ concrete mattresses represent a cutting-edge solution for ports seeking to deepen their berths and upgrade their infrastructure. By providing critical seabed stabilisation and structural support, these mattresses allow ports to meet the demands of modern shipping while minimising environmental impact and operational disruptions.
For port owners and infrastructure managers, investing in in situ concrete mattresses is not just a way to enhance berth depth—it’s a strategic move towards ensuring future competitiveness, sustainability, and efficiency in an ever-evolving maritime industry.
