THE tetrapods They are hydraulic engineering works intended for the coastal defensemade of concrete, which act as breakwaters and are characterised by various geometric shapes which allow for optimization of hydraulic and structural performance. They can be partially submerged and have, specifically, the function of protecting the shore profile from the unwanted effects of the sea in adverse weather conditions.
A premise: artificial coastal protection structures
Speaking in general about coastal defense structures, we can always distinguish between natural and artificial ones. A work of natural defense is, for example, the beach. However, when this is absent, it is necessary to introduce into the inner area of the coast some artificial protection structuresThese include, for example, reefs or breakwaters.
These works allow for dissipate wave energy and prevent more or less extensive flooding of coastal areas in times of high maritime “agitation”. In general, we can say that they are structures that are used for prevent the impact force of the water generate a unwanted variation of the coastal profile, permanent or temporary.
Breakwater barriers can be either emerging than submergedas in both cases they have the ability to counteract the kinetic energy of the moving waves, although with different capacities. The shape, height and length of the barrier represent the design parameters that strongly depend on the climatic conditions that can occur in the area of interest, the direct cause of the wave motions that translate into the aforementioned problems.
What are tetrapods and what are they used for?
The tetrapod is a particular form of breakwater structuremade up of elements in prefabricated reinforced concrete (i.e. made far from the actual area of use), equipped with 4 feet and a central body where these feet converge geometrically. Depending on the size, they can weigh from 1 to 8 tons. Using this particular geometric configuration has two advantages:
- The first advantage is that hydraulic character, as the shape of the single foot of the tetrapod allows for the generation of energy dissipation which simultaneously allows the flow of water to be accompanied in crossing the obstacle. This geometric effect limits the impact of the flow of water and, furthermore, allows the water itself to flow into the porosity generated by the aggregate system of multiple tetrapods. In fact, in their aggregation, gaps are formed where the water can flow, even if with difficulty: it is precisely this difficulty that becomes the desired dissipation of energy.
- The second advantage is that structural character: in fact, the particular shape of the single tetrapod allows for the creation of a mechanical union between the individual elements which has its own load-bearing capacity, independently of the use of any additional mechanical organ or further finishing materials, such as mortars.
The geometric configurations
Coastal defense can be achieved with various hydraulic engineering works, of increasing complexity (think, for example, of the Mose). Some works, in many cases, are built underwater and are therefore not normally visible. In the case of breakwater barriers, tetrapods or not, we can have a localized geometric configuration near the coast (almost to form a dam), or far from the coast (to possibly also protect a port area). The needs of the case are taken care of by specific technicians who, in relation to the information at their disposal, design the best solution to obtain a effective coastal defense.
