Because they are invisible, it is easy to forget the primordial role of foundations in a construction. The choice of the type of foundation is made according to the quality of the ground. We must find the "good ground". For this it is sometimes necessary to dig deep. Well excavations make it possible to get this good soil.
Characteristics of well excavations
Theoretically a well search is a semi-deep excavation cylindrical or square shape.
Cylindrical, it makes about 1 m in diameter.
Square, it is at least 0.80 m wide.
The dig in well is usually bent or circled and filled with large concrete that is to say a coarse concrete containing coarse aggregates.
The use of well excavations
Well searches are used in 2 cases:
- To build very important buildings.
- To pick up the good soil that is to say, a floor that can support the construction.
Wells filled with large concrete will anchor in the layer of good soil. The loads are transmitted by peak effect that is to say the vertical support on the carrier soil. Or by side rubbing effect. The soil layer surrounding the well providing a resistance to penetration.
This phenomenon makes it possible to anchor foundations even in poor soil. On the other hand it is necessary to go down more deeply.
On the other hand, if the good ground is located at more than 6 m of depth, it is the technique of the piles which is used. Piles of metal or concrete are buried in the ground.
In urban areas, the pressure of real estate is strong, the technique of micro-piles is increasingly used to build single-family homes on low-load land.
Find the right floor
The good ground is one of ground sufficiently resistant to support the weight of a construction and its contents. Without forgetting that the construction will undergo various constraints like the wind, the weight of the snow, the succession of episode of frost and thaw, the drought, etc.
It is important to know the nature of the soil and subsoil before starting a construction. And even for the construction of an individual home, the use of a soil survey by a geotechnician can avoid many disorders such as structural cracks or a house that collapses.
These are the results of this study that will determine the type of excavation to be carried out in order to sink the foundations.
Good to know: Before starting the construction of your house, do not hesitate to go to the town hall to consult the Local Plan of Urbanism (PLU). Check if the municipality has put in place a Risk Prediction Plan (PPR) which determines the flood zones, the problems of shrinkage and swelling of clays, the risks related to drought or frost. All these elements will be good indications for dig digging at the right depth.