Concrete wave breakers work primarily by dissipating the energy of incoming waves, rather than simply blocking them. This process significantly reduces the waves' force and height before they reach the shoreline or protected structure.
Instead of presenting a solid, impenetrable wall that reflects wave energy (often causing issues like erosion elsewhere or stronger returning waves), concrete wave breakers are typically constructed using porous or complex structures made of large, specially shaped concrete units.
The Principle of Wave Energy Dissipation
The fundamental idea is to break up the wave's structure and absorb its power. When a wave hits a solid vertical wall, its energy is mostly reflected back. When it encounters a porous structure like a pile of large concrete armour units, water can flow into and around the structure. This internal movement and friction within the breaker material, combined with turbulence, convert the wave's kinetic energy into heat and dissipated energy.
Examples: Tetrapods and Interlocking Units
One well-known type of concrete armour unit used in wave breakers is the Tetrapod. These are distinctive four-legged concrete structures. As stated in the reference, Tetrapods are made of concrete, and use a tetrahedral shape to dissipate the force of incoming waves by allowing water to flow around rather than against them, and to reduce displacement by interlocking.
This design is highly effective because:
- Dissipation: The open spaces between the interlocking Tetrapods allow water to flow through the structure. This porosity reduces the direct impact force of the wave compared to hitting a solid wall, distributing the energy over a larger area and through turbulence within the structure.
- Interlocking: The unique shape allows the units to fit together, creating a stable, interconnected mass. This interlocking mechanism is crucial for the structural integrity of the wave breaker, preventing individual units from being easily displaced or washed away by powerful waves.
Other types of concrete armour units (like Dolosse, Accropode™, etc.) also utilize complex shapes designed for both energy dissipation and interlocking stability.
Why Porous Structures Are Effective
| Structure Type | Wave Interaction | Outcome |
|---|---|---|
| Solid Wall | Primarily reflects energy | High impact force, potential for reflection |
| Porous Breaker | Dissipates energy by flow/turbulence | Reduced impact force, less reflection |
This dissipation process effectively reduces the wave height and energy reaching the area behind the breaker, protecting coastlines from erosion, safeguarding harbours and marinas, and stabilizing breakwaters.
In summary, concrete wave breakers, especially those using specially shaped units like Tetrapods, work by strategically interacting with wave energy, using their design to dissipate force through porosity and maintain their structure through interlocking, offering vital coastal protection.
