Introduction
Modern ports are under growing pressure to accommodate larger vessels, minimise downtime, and extend the service life of their infrastructure. Scour protection plays a vital role in this, safeguarding quay walls, piled jetties, and other marine structures from erosion caused by vessel propulsion and tidal currents.
Among the options available, sealed protection using in situ concrete mattresses offers a uniquely efficient and long-lasting solution. It enables thinner protection, maximises usable berth depth, reduces material requirements, and provides a more stable foundation for marine infrastructure.
This article explains what sealed protection is, why it matters, how it differs from traditional methods, and how it is practically achieved using in situ concrete mattress systems.
What Is Sealed Protection — And Why Does It Matter?
Sealed protection refers to a form of scour protection that is closed to flow—across the mattress surface, through its joints, and around its edges. The aim is simple but powerful: eliminate any path for water to penetrate under the protective apron.
This approach transforms scour protection from a reactive system into a proactive, engineered barrier. When sealed correctly, it:
- Distributes hydrodynamic loads across the entire mattress apron.
- Requires far less deadweight, enabling thinner protection layers.
- Prevents flow-induced uplift, which is a common failure mode.
- Maintains seabed integrity, reducing long-term maintenance.
- Enables full utilisation of berth depth, essential for port deepening and efficient new quay construction.
In short, sealed protection improves performance, reduces costs, and supports sustainable infrastructure.
Sealed vs. Unsealed Scour Protection
The distinction between sealed and unsealed protection is fundamental to performance.
Unsealed Systems
Traditional systems such as rock armour or pre-cast flexible block mattresses rely on mass, layering, and flexibility. These methods:
- Allow flow between and beneath protection elements.
- Rely on large material volumes for stability.
- Are vulnerable to edge failure and under-scour caused by trapped flow pressure.
- Require thicker profiles—which reduce available draft and increase wall height or dredging needs.
Sealed In Situ Concrete Mattresses
In contrast, a properly sealed concrete mattress:
- Forms a continuous concrete apron tailored to the seabed contours.
- Prevents water ingress through joints or edges.
- Can be up to 7 times thinner than rock armour for the same performance.
- Enables scour protection to be placed at the lowest structural level, maximising vessel clearance.
- Requires less material and transport, reducing cost and carbon footprint.
This shift in behaviour—from resisting flow by weight to eliminating flow paths altogether—is the key reason why sealed protection outperforms older methods.
How Sealed Protection Is Achieved with In Situ Concrete Mattresses
Achieving true sealed protection relies on specific design and construction principles. At Proserve, our in situ concrete mattress systems are designed around four core sealing principles:
- Sealed at the Structure
- For quay walls, a concrete bolster is cast at the base to close the joint between wall and mattress.
- For piled revetments, the fabric formwork is wrapped and sealed around each pile, preventing bypass flow.
- Sealed Between Panels
- Mattress panels are zipped or sewn together with grout-tight joints (such as ball and socket seams).
- Once filled, they behave as an interlocked concrete slab—resisting joint separation during operation.
- Fully Filled to Design Thickness
- Mattresses are pump-filled in situ with high-fluidity concrete, reaching the full design height and ensuring consistent deadweight.
- Full fill is essential to resist propeller suction and hydrodynamic uplift.
- Robust Edge Protection
The edge of any mattress is the most vulnerable area for under-scour. We use tailored edge details to suit site conditions:
- Embedded edge trench — Passive edge sealing in all soil types, with space for future rock placement.
- Rock falling edge apron — Ideal for sandy soils and design scour depths of 4–6m.
- Hinged edge — Heavy edge blocks that pivot into developing scour holes, reducing the need for initial trenching.
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- Stiff clay trench with concrete bolster — For slowly eroding beds, this detail offers long-term edge integrity.
Preventing Underscour with Edges - Blog Article
Each edge solution contributes to a fully sealed system, capable of resisting extreme flow conditions without compromising berth draft or structural integrity.
Conclusion
Sealed protection using in situ concrete mattresses represents a significant advancement in port scour protection. By preventing flow entry beneath and between protection elements, it delivers:
- Thinner, more efficient protection
- Reduced material and carbon footprint
- Better draft clearance and wall optimisation
- Long-term durability and lower maintenance needs
With decades of proven performance across port structures worldwide, sealed in situ concrete mattresses offer engineers and port owners a smarter, more reliable approach to protecting marine infrastructure.
Maximising Berth Deepening - Blog Article
Key Benefits of Sealed Protection
✅ Distributes Forces, Requires Less Deadweight
Spreads flow and suction loads over the full mattress area, avoiding the need for heavy protection elements or thick layers.
✅ Thinner, More Efficient Protection
Up to 7x thinner than rock armour—maximising usable water depth and structural efficiency.
✅ Material and Carbon Savings
Significantly less concrete and transport required than rock systems; reduces total environmental impact.
✅ Faster Installation
Pump-filled from shore with no need for heavy rock-handling equipment or extensive marine plant.
✅ Long-Term Stability
Resists uplift, abrasion, and high-flow conditions with minimal maintenance required.
