WMesh Coastal erosion control barriers
THE "WMesh" SYSTEM WAS DESIGNED TO IMPROVE TRADITIONAL STONE BREAKWATERS FOR COASTAL PROTECTION.
Traditional stone breakwaters have detrimental collateral effects for the coastal area, the seabed, and the surrounding environment.
The main problems related to stone breakwaters are the following:
- poor water recirculation and therefore stagnant, turbid, and malodorous water
- muddy seabed
- excessive algal accumulations
- sudden level drop after the breakwater
- more depth close to breakwater interruptions
- irregular seabed with dangers for swimmers
- irregular foreshore with promontories and creeks
- visual obstacle on the horizon interfering with rescue operations.
Although the use of breakwaters is widespread for coastal protection, in some cases breakwaters worsened erosion phenomena.
the reason is that such structures relevantly change the direction of marine currents, and the consequences can only be assessed after installation.
If, on the one hand, breakwaters reduce wave impact, on the other hand they cause a level difference between beach and seabed after the breakwaters themselves, which causes crosswise currents carrying sand offshore and create dangerous dips for swimmers.
The WMesh anti-erosion barrier was designed to reach the following objectives:
- dissipate wave energy
- counter-act marine current
- foster sand input and create shallows
- contrasting sediment removal from coasts and lengthen beach nourishment lifetime.
Without radically altering the environment where it is installed.
- the deflectors composing the modules deviate incoming currents upwards, thus oxygenating water
- the whole barrier becomes a marine habitat regeneration area
- it prevents trawling close to the coast.
"Seafloor" barrier means the barrier lies under the water surface, thus with a low environmental impact, it does not interrupt the horizon and does not interfere with rescue operations.
Features and operating principle
The "WMesh" structure is composed of precast reinforced concrete modules manufactured by Edil Impianti2 with CE-certified materials.
Designed to be transported with traditional lorries to reduce shipping and installation times, the weight was calculated so to arrange the modules on the seabed with small dredges.
The whole structure is placed onto the seabed by installing the modules next to each other in a raw, by using specific hooks to lay and remove the modules.
Since the structure is permeable, the barrier can be continuous and parallel to the coastline, with no dangerous interruptions for water recirculation, as the sea water can flow through the whole structure.
If necessary, the WMesh barrier can follow irregular coastlines or it can be adequately oriented to counteract currents.
In front of ports or channels, the barrier can be interrupted or lower modules can be used in order to enable ship and boat transit.
The module shape makes the barrier resistant against heavy sea in all directions. The module deflector elements can deviate currents upwards, thus reducing wave energy and crosswise currents, which are the main cause of coastal erosion in many cases.
The whole structure is made of concrete in compressive strength class C45/55 (RCK 55N/mm²) compliant with the UNI EN 206-1 and UNI 11104 regulations for the XC4 exposure classes (resistance to carbonation-induced corrosion), XS3-XD3 (resistance to chloride-induced corrosion, also from marine sources), XF3 (resistance to frost/thaw cycles with or without de-icing salts), XA2 (resistance to aggressive chemical environments in natural soil and ground water), certifications and tests by CIRI EDILIZIA E COSTRUZIONI, internal improved-adhesion steel reinforcements checked in our plant, steel fibers GREESMIX5, electro-welded square mesh B450C.
Some fluid-dynamic tests have been carried out first of all with computer simulation to prove that the structure can work with marine currents with different wave height.
Strong current intensity simulations made it possible to assess how the structure can react under specific conditions, this is very important to design the geometric structure of the modules to receive crosswise marine currents as well.
Based on the simulation results, the structure was proved to be effective, and although permeable, it can deflect incoming currents upwards.
Module geometry furthermore determines a dead area behind the structure in the lower area of the seabed, thus enabling settling and progressive sedimentation.
Wave simulation was carried out in order to prove whether the submerged structure could possibly interfere with swell.
Several tests confirmed that when wave height increases, also the structure interference increases thus reducing wave energy.
Tests on scale models
Afterwards, experimental tests have been commissioned for selected Departments for Hydraulics of some Italian Universities.
The tests were 2D and 3D tests, with fixed seabed (with no sand) and movable seabed (with sand), using different WMesh scale models.
These tests confirmed several crucial features:
- structure stability, even with heavy sea
- no erosive currents (which would also compromise stability, by the way)
- wave energy dissipation
- current reduction
Without significantly altering the surrounding environment.
Also visit the website: http://www.wmesh.it/