Accropode
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Accropode blocks are wave-dissipating concrete blocks designed to resist the action of
wave In physics, mathematics, engineering, and related fields, a wave is a propagating dynamic disturbance (change from List of types of equilibrium, equilibrium) of one or more quantities. ''Periodic waves'' oscillate repeatedly about an equilibrium ...
s on
breakwater Breakwater may refer to: * Breakwater (structure), a structure for protecting a beach or harbour Places * Breakwater, Victoria, a suburb of Geelong, Victoria, Australia * Breakwater Island, Antarctica * Breakwater Islands, Nunavut, Canada * ...
s and coastal structures.


History

The Accropode is a single-layer artificial armour unit developed by Sogreah in 1981. Accropode concrete armour units are applied in a single layer. The Ecopode armour unit with a rock-like appearance was developed by Sogreah to enhance the natural appearance of concrete armourings above low water level. A patent application was filed in 1996. The color and type of rock-like appearance can be specified to match the surrounding landscape. In 1999, Sogreah modified the original Accropode shape by chipping away excess materials and adding friction features in the form of small pyramids. A patent application was filed for this modified shape. In 2004 further modifications to the 1999 shape were made, resulting in the Accropode II. The shape modifications are intended to increase interlocking. Accropodes are not produced by the patent holder, but are fabricated and installed by a contractor who in return pays a license fee. Such an agreement involves certain technical support activities to ensure the correct application of the protection system. After the patent has expired (like it is for the Accropode I) anyone can make a block with this shape, but one is not allowed to call it Accropode, because the name is still a protected trademark. And the contractor will not have technical support the (former) patent holder. In 2018 a shoreline protection near
Colombo Colombo, ( ; , ; , ), is the executive and judicial capital and largest city of Sri Lanka by population. The Colombo metropolitan area is estimated to have a population of 5.6 million, and 752,993 within the municipal limits. It is the ...
,
Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
has been made by the Chinese contractor
China Harbour Engineering Company China Harbour Engineering Company Ltd (CHEC) is an engineering contractor and a subsidiary of China Communications Construction Company (CCCC), providing infrastructure construction, such as marine engineering, dredging and reclamation, road a ...
. The contractor has applied the ''Chinapod'', looking identical to te Accropode I, but without guarantee and support of CLI (the former patent holder).


Design


Hydraulic stability

Specified stability coefficients at design stage: * Hudson’s design KD values: ** 15 on trunk sections (16 for Accropode II) ** 11.5 on roundheads (12.3 for Accropode II) * Van der Meer stability number : NS = HS/(∆ Dn50)= 2.7 (2.8 for Accropode II) where: HS = significant wave height ∆ = relative mass density Dn50 = nominal diameter These coefficients are valid for armour slopes from 3H/2V to 4H/3V and for seabed slopes up to 3%. The uneven surface of the Ecopode improves interlocking by friction, thereby increasing hydraulic stability.


Implementation

Fork-lifting is effective for handling the small to medium size units, whereas large units are handled by sling. Placement for breakwaters generally requires a crane or a barge-mounted crane. The units can be stored one on top of the other, and placed in a random attitude to obtain the specified packing density. The proper packing method provides an adequate coverage on breakwater slopes. The use of a remote-release hook is used for placing the unit, while underwater placements may be enhanced by GPS, adhering to a theoretical grid.


Gallery

File:Accropode Breakwater.jpg, Accropode blocks on offshore breakwater roundhead. File:Accropode block storage.jpg, Storage of Accropode II blocks. Image:Forklifting.jpg, Accropode II on forklift. Image:Acctruck.jpg, Accropode on truck. File:Accropode offshore.jpg, Placing Accropode blocks from land. Image:Accropodedigue.jpg, Accropode blocks on breakwater. Image:Placing with a crane.jpg, Placing with a crane Image:AccropodeMonitoring.jpg, Monitoring


See also

*
Breakwater (structure) A breakwater is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges. Breakwaters have been built since antiquity to protect anchorage (maritime), anchorages, helping isolate vessels ...
*
Erosion control Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development, coast, coastal areas, Bank (geography), river banks and construction. Effective erosion controls handle surface runoff and are ...
*
Riprap Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. ...
*
Artificial reef An artificial reef (AR) is a human-created freshwater or marine benthic structure. Typically built in areas with a generally featureless bottom to promote Marine biology#Reefs, marine life, it may be intended to control #Erosion prevention, erosio ...
*
Coastal erosion Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of Wind wave, waves, Ocean current, currents, tides, wind-driven water, waterborne ice, or other impacts ...
*
Ocean surface wave In fluid dynamics, a wind wave, or wind-generated water wave, is a surface wave that occurs on the free surface of Body of water, bodies of water as a result of the wind blowing over the water's surface. The contact distance in the wind directi ...
*
Seawall A seawall (or sea wall) is a form of coastal defense constructed where the sea, and associated coastal processes, impact directly upon the landforms of the coast. The purpose of a seawall is to protect areas of human habitation, conservation, ...
* KOLOS *
Xbloc An Xbloc is a wave-dissipating concrete block (or "armour unit") designed to protect shores, harbour walls, seawalls, breakwaters and other coastal structures from the direct impact of incoming waves. The Xbloc model was designed and developed ...


References


General references to Accropode design

* Ciria-CUR (2007)
Rock Manual - The use of rock in hydraulic engineering
* K. d'Angremond (2004)
Breakwaters and closure dams
* N.W.H. Allsop (2002)
Breakwaters, coastal structures and coastlines
* J.W. Van der Meer (1988)
Rock slopes and gravel beaches under wave attack
* Delft Hydraulics Laboratory (1987)
Stability of rubble mound breakwaters - Stability formula for breakwaters armoured with Accropode (report H 546)
* U.S. Army Corps of Engineer Waterways Experiment Station (WES) - Shore Protection Manual (1984)

based on Hudson's extensive work in the fifties.


External links


Concrete Layer Innovations



MEDUS (Maritime Engineering Division University Salerno)

Concrete Layer Assistance and Survey CLAS: Specialized Company for ACCROPODE ACCROPODEII CORELOC ECOPODE and Xbloc armouring breakwaters
{{coastal management Coastal engineering Wave-dissipating concrete blocks French inventions