- Case study
- Szczecin New
- Poland
Berth Deepening Scour Protection for an Existing Quay Wall, Port of Szczecin, Poland
The port needed to take larger vessels, which meant dredging an existing berth around 2 m deeper without undermining a wall that was never designed for that depth. Every millimetre of protection thickness is depth the wall does not get back. The Luxemburg return wall was also identified as unstable and in need of reinforcement.
Location
Szczecin, Poland
Client
Port of Szczecin
Designer
Aarsleff
System
Concrete mattress
Period
2024
Results at a glance
Sealed apron installed
Concrete mattress over the dredged berth pocket
Extra depth achieved
Berth taken from −10.6 m to −12.5 m for larger vessels
Custom-made offsite
Averaging 185 m², each filled with 41 m³ of concrete
Contents
- The berth was deepened from −10.6 m to −12.5 m so larger vessels could dock, without compromising the stability of the existing quay wall.
- 11,000 m² of concrete mattress was installed by contractor Aarsleff over the dredged pocket.
- When deepening an existing quay, the thinner the protection, the more depth the existing wall can give up: a sealed interlocking layer needs no deadweight to resist propeller flow.
- 71 panels averaging 185 m² were made offsite, each filled with 41 m³ of concrete pumped from the quayside in about 6 hours.
- The apron edge sits in a trench with 4 t hinged edge blocks tied in, designed to drop independently and heavy enough to resist being flipped by trapped flow pressure.
The constraints
The objective at Szczecin was to increase the berth depth from −10.6 m to −12.5 m, adding around 2 m so larger vessels could dock, without compromising the stability of the quay wall. Installation of 11,000 m² of concrete mattress scour protection was carried out by contractor Aarsleff.
The berth pocket was dredged to its maximum depth. Extra measures, including ground anchors at selected locations, were put in place to maintain the structural integrity of the quay wall.
tolerance
required
The solution
When deepening an existing quay wall, using the thinnest possible protection maximises the depth achievable with the wall you already have. That is the whole argument for a sealed system here.
The insitu concrete mattress creates an interlocking layer that gives sealed scour protection, distributing hydrodynamic forces evenly across the apron and producing a stable, thin protective layer. Rock armour and unsealed mattress systems, by contrast, need extra deadweight to counteract hydrodynamic forces from propeller action and to resist trapped flow pressure, and that added weight increases the thickness of protection required.
Table 2 sets out the panel and filling figures behind the installation.
output
Constructability and installation
The whole sequence runs off the quay. Formwork is made offsite, lowered in and unrolled on the dredged bed, and filled with concrete pumped from the quayside, with dive teams moving the hose between filler points.
Roll out on the seabed
The formwork, custom-made offsite to the precise site dimensions, is rolled out on the dredged bed along the quay. It is fabric formwork, so it takes the shape of the bed it lands on.
Secure in position
The panels are secured on the bed before any concrete goes in, so it holds position as it fills.
Fill from the quayside
Concrete is pumped from the quay. Divers move the filling hose between filler points as the panel fills, each filling taking about 6 hours.
Work the quay in parallel
How many panels go in per day depends on how many working areas are open along the quay and how many dive teams are in use.
Trench and tie the edges
The apron edges are placed in a trench with the hinged edge block detail tied into the main slab.
The apron edge
For long-term protection it is vital that the concrete apron is not undermined at its edges. The edges are placed in a trench, which includes a hinged edge block detail.
These hinged edge blocks are tied into the main concrete apron, weigh 4 t each, and are designed to drop independently. That gives the apron additional protection against scour before any maintenance is needed, and the blocks are heavy enough to resist being flipped by trapped flow pressure.
Outcome
The berth carries 11,000 m² of sealed apron, taking the quay from −10.6 m to −12.5 m so larger vessels can dock, without compromising the stability of the quay wall. Because the layer is sealed and interlocking rather than deadweight, the protection is thin, and the depth stays in the water. The same principle applies wherever berth scour protection has to fit inside a fixed dredge box.
For long-term protection it is vital that the apron is not undermined at its edges, which is what the trench and the hinged edge blocks are there to prevent.
Who did what on this project
Owner of the quay and the berth deepening programme.
Carried out the installation of the concrete mattress scour protection.
Concrete mattress system, panel design and the hinged edge detail at the apron perimeter.
Continue
Jeddah Port, block wall deepening
The same problem on a block wall in Saudi Arabia: berth scour protection by concrete mattress, letting an existing quay be dredged deeper.
Read the case study →Concrete mattress
How the form is filled, the variants, and why a sealed interlocking layer needs no deadweight to resist propeller flow.
Read →Quay walls
Szczecin is a block wall taken deeper. This is the same problem set out generally: protecting the bed at the toe of an existing wall.
Read →Deepening a berth against an existing wall? Send us the as-built section and target depth.
Send us the as-built section of the wall and its toe, the depth you need and the vessel classes, and we will come back with an outline approach: apron thickness, extent and edge detail, and how much depth the wall can give up. If the wall cannot take it, we will say so.
- As-built section of the wall and its toe
- Target depth and dredging tolerance
- Vessel classes and propulsion
- Berth availability and programme