Unreinforced Concrete Armour Units developed to satisfy all site conditions

1. Armour units





(First generation) : "The benchmark in single-layer armouring technology"

(Second generation) : "Technology, experience and cost-effectiveness condensed into a single armour unit"

"The coastal protection solution that blends most effectively into the surrounding landscape"

"Highly dissipating and cost-effective system for breakwater armouring"

2. Quick overview of CLI armour solutions

CLI Single-layer systems consist of un-reinforced concrete armour units specifically designed for the protection of exposed coastal structures. Their combined qualities produce solutions which are as reliable as conventional double-layer systems and at the same time cost-effective.

The ACCROPODE™ artificial concrete unit is the first single-layer artificial armour unit developed by SOGREAH and has been widely used with nearly 200 projects to date. Read more

This technology has proved to be successful on a great number of breakwaters projects worldwide during the 30 past years with a good hydraulic stability and a legendary sturdiness using ordinary mass concrete. Pioneer in single layer technology, this artificial unit has become the benchmark for current breakwater armouring.

ACCROPODE™ II Based on the experience gained with first generation ACCROPODE™ on a substantial number of projects, the shape of the ACCROPODE™ has been improved to make a new step forward : Read more

Invented and patented by SOGREAH since 1999 for particularly exposed sites and difficult work conditions, the new generation known as ACCROPODE™ II has been made available for industrial applications in 2003-2004. 

The optimised shape naturally increases interlocking while new features minimise rocking and settlement, maximise energy dissipation, reduce wave reflection and run-up/overtopping.

A simplified placement method has been established since the random attitude of each unit is more naturally obtained, with fewer constraints in terms of orientation, thus enabling the units to be placed much more rapidly on site using simple rules. The projects completed to date confirm that the constructed armour layers meet the acceptance criterion irrespective of the site constraints and production targets. 

ECOPODE™ With its rock-like appearance and adaptable colour, the ECOPODE™ unit, patented in 1996, enables to meet the aesthetic requirements on sensitive sites, and blends perfectly into the surrounding landscape. Read more

Moreover, most of the improvements made to the ACCROPODE™ II unit have been drawn from the ECOPODE™ unit development. The ECOPODE™ unit’s rock-like skin enhances the appearance of this man-made system with a natural look, making it unobtrusive in sensitive sites such as marinas, coastal protection works and land reclamation sites within populated urban areas. Clients can choose the type of rock-like skin and colour which are best suited to the surrounding landscape.

Several types of rock finish can be produced: limestone, sandstone and basalt with associated typical colours. For very sensitive projects, the exact type and colour of rock can also be reproduced to suit Clients requirements.

  • ECOPODE™ armours consume 3 to 4 times less material than natural rock armours of equivalent stability, thus reducing the constraints linked to the extraction and haulage of large rocks which are destructive to the environment (disruptive traffic, noise, pollution, etc).
  • ECOPODE™ can be placed in the visible upper part of the breakwaters, above the low water line, over ACCROPODE™ II units which have similar geometry. The other assets of the ECOPODE™ units just like the ACCROPODE™ II units are its improved hydraulic performance, greater sturdiness and easier placement. These aspects have been checked and validated since 2003 by specific studies and in real site conditions.
  • The rock appearance of the ECOPODE™ units requires a specific type of mould. SOGREAH has performed research and investigations to find the most effective mould system for casting this complex shape.
  • The mould system has evolved from the first ECOPODE™ mould made of steel with added polyurethane lining in the inside, to the current mould system consisting of two symmetrical shells made of fibre glass, backed by a steel spider frame mounted on wheels. Thus, the inside of the shells is architectured by means of appropriate coatings to obtain the rock-like appearance.

The CORE-LOC™ armour unit was developed and patented in the mid-1990s by the U.S. Army Corps of Engineers (USACE) Coastal and Hydraulics Laboratory. Read more

  • It is now widely considered for breakwater projects requiring reliable and cost-effective protection.
  • This armour unit is ideally suited for sites exposed to moderate waves.
  • The high porosity ratio (60% air voids) within the armour reduces the overtopping and thus allows particularly efficient wave energy dissipation.

3. Standard sizes

The standard ACCROPODE™ units sizes range from :
0.8 to 28 m³
The standard ACCROPODE™II units sizes range from :
1.0 to 28 m³
The standard CORE-LOC™ units sizes range from :
1.0 to 11 m³
The standard ECOPODE™ units sizes range from :
1.0  to 10 m³
 The indicated unit volumes are standard values. However, other values can be made to suit the requirements of every project, notably other unit sizes already used in the past for which moulds are already available.

4. Hydraulic stability

During design stage, the stability coefficients are selected as a function of the achievable packing density on site.

The standard Hudson’s design KD values for slightly breaking or non-breaking wave conditions are: - 15 on breakwater trunk sections
- 11.5 on breakwater roundheads 
- 16 on breakwater trunk sections
- 12.3 on breakwater roundheads
- 16 on breakwater trunk sections
- 13 on breakwater roundheads
- 16 on breakwater trunk sections
- 12.3 on breakwater roundheads
The recommended Van der Meer stability number is:  NS = HS/(∆ Dn50)= 2.7  NS = HS/(∆ Dn50)= 2.8  NS = HS/(∆ Dn50)= 2.8  NS = HS/(∆ Dn50)= 2.8

 Where :

  •    HS =  significant wave height
  •    ∆ =  relative mass density 
  •    Dn50 = nominal diameter

These coefficients are valid for armour slopes from 3H/2V to 4H/3V. However, for breaking waves and   seabed slopes greater than 1%, adapted values shall be applied.

5. Robustness

Stress distribution in the unit was initially analysed using finite-element methods and full-scale drop tests were conducted to check the sturdiness of the unit using ordinary mass concrete.

Experience on over a hundred and eighty projects has demonstrated the excellent behaviour of the ACCROPODE™.

Comparative finite-element studies have demonstrated that the ACCROPODE™ II unit has improved robustness compared with the first-generation ACCROPODE™,  which is recognized worldwide for its ease of placing and excellent ‘‘no damage’’ records and reputation.

The structural strength of the ECOPODE™ may differ slightly according to the type of rock-like skin selected. However, the minimum unit strength required will at least match the strength of the unit used underwater, as the shape and skin effect have been designed accordingly.

6. Practical aspects

 Choose an unit type to see its practical aspects :