A swimming pool installed in the ground must be able to withstand the pressure of the ground from the outside. Also, the pool must not be deformed from the outside by the pressure of the water. Since a GRP basin is basically an elastic-plastic body, it cannot withstand earth pressure or water pressure on its own. The backfilling basically takes over this task. The material and thickness of the backfill must enable the mentioned pressures to be absorbed. To prevent the backfill itself from shifting, it is “spread out” in the area of the pool floor by building a concrete slab between the backfill. A ring beam is placed on top to prevent the backfill from deforming in the upper area. Thus, the entire backfill construction consists of three elements: Base plate, backfill, and ring beam. The resulting overall construction provides so much strength that the pressures from the inside or outside are absorbed. Additionally, the kerbstone and the plating around the basin have permanently fixed support.
In some federal states, the building permit for pools requires static calculations for this construction, which can be obtained from the pool supplier or the supplier of the backfill system.
Note: As shown above, the base plate is subjected to “compression”. This is why the base plate only needs to be 10 cm thick and does not require steel reinforcement.