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Piled Jetty Scour Protection
Concrete mattress provides unique revetment protection from both vessel and wave action. A sealed concrete apron to the wall and around the piles, prefabricated porosity holes enable effective wave run down, ensuring the slab is not lifted. The system has 50 years of proven usage on revetments.
Revetment Scour
The geotechnical stability of slopes surrounding piled jetties in ports is a critical factor in ensuring the structural integrity and longevity of these maritime infrastructures. Piled jetties are often exposed to significant environmental forces, including wave action and vessel-induced currents, which can lead to scour – the removal of sediment around the piles and slope areas. Without adequate protection, this scour can undermine the slopes, causing erosion and instability, potentially leading to structural failure.
To mitigate these risks, effective scour protection measures such as mattresses or rock armours are essential. These measures help maintain the stability of the slopes by absorbing and dissipating the energy of waves and currents, thus preventing the erosion of sediments and ensuring the continued safe operation of the jetties
Construction Sequencing Benefits
Concrete mattresses offer significant advantages over traditional rock armour for scour protection at piled jetties, particularly regarding installation and logistical efficiency. One key benefit is that concrete mattresses can be installed beneath the jetty deck, allowing scour protection work to proceed independently of other construction activities. This flexibility means that work on the deck can continue simultaneously, removing scour protection from the critical path and significantly improving project scheduling.
The concrete apron formed by the mattresses effectively distributes hydrodynamic forces across the entire surface, providing a stable and robust barrier against scour. In contrast, rock armour relies on the individual deadweight of each rock to prevent displacement, requiring rocks to be up to seven times thicker than an equivalent concrete mattress. Due to the specific size and weight of the required rock, suitable materials may not be available locally, making sourcing challenging. Transporting these large rocks from distant locations can be prohibitively expensive, further complicating the logistics and increasing project costs.
Installation Underneath Deck
By eliminating the need for large, hard-to-source rock units and providing a streamlined installation process, concrete mattresses offer a more practical and cost-effective solution for maintaining geotechnical stability. This approach ensures efficient project completion and reduces delays, making concrete mattresses the preferred choice for scour protection at piled jetties.
Jetty Refurbishment
When refurbishing or deepening an existing jetty, concrete mattress enables scour works to again proceed under the deck. Localised water dredging can be used to prepare the slope ready for mattress installation.
Installation
The formwork, like traditional land-based systems, is designed for casting concrete. This lightweight formwork is easily handled and positioned underwater, allowing the casting of interlocking concrete aprons over uneven surfaces, ensuring full thickness on slopes.
Installation Process
- The diver rolls out the formwork and secures it around the piles and at the top of the slope.
- Mattress 2 is lowered and connected in the same manner.
- Mattress 1 and 2 are zipped together.
- Mattress 1 is pump-filled from the quayside, using a tremie technique, starting at the bottom of the slope. The diver moves the filling hose upwards as filling progresses.
- This process is repeated: Mattress 3 is zipped on, and Mattress 2 is filled.
This method ensures the mattress fills to its full thickness, forming interlocking shear joints between the panels.
Key Installation Preparation:
Proserve ensures the formwork is customised to the project’s needs to minimise diver time and guarantee successful first-time grouting. With specialist expertise, Proserve engineers collaborate with contractors on construction preparation and mix development using local materials to enable rapid installation once construction begins.
Case Studies
In-situ mattresses have been used on revetment slopes for over 40 years in container and cruise vessel ports. Please refer to the case studies below:
