Special foundations include all the techniques and processes used in the creation of foundations for Civil Engineering works, buildings and road, motorway and railway infrastructure, excavation, support and soil consolidation. This work is carried out by companies highly specialized in the field, such as the company SEF managed by Jean-Yves and Michael Stoquer, father and son respectively. Jean-Yves Stoquer is a building engineer specialising in special foundations (piles, micropiles, injection work, geotechnical studies among others) while his son is a graduate of the prestigious ESSEC business school.
As special foundations are an extremely complex field of building work with many different methods, the soil injection technique will be dealt with here.
What is soil injection?
Soil grouting consists of filling the voids in the ground with a suitable, cement-based grout, mainly to improve the cohesion and mechanical characteristics and to reduce the permeability of the soil. The grout is sent into the ground from the surface or directly into openings such as shafts or galleries. Depending on the problem encountered in the soil, the grout is injected to consolidate it, fill it, compensate it, make it more watertight or seal it.
- Consolidation: this technique makes it possible to improve the mechanical resistance of a ground to facilitate excavations, the crossing of difficult crossing areas or to increase the general bearing capacity of a foundation block. In addition, it makes it possible to consolidate intermediate foundations that can be destabilised by the excavation of a nearby excavation.
- Filling: this technique is used to fill natural cavities in the ground, such as underground quarries or annular voids.
- Compensating: this method makes it possible, during the excavation of a tunnel for example, to limit and compensate for the settling resulting from the deconfinement of the ground by injecting the soil located above it. There are three different grouting techniques: injection by impregnating existing voids with a fluid grout, injection by slaking the massif and filling it with a fluid grout and injection by clamping a thick grout.
- Sealing: the objective of this technique is to create vertical or horizontal screens to make the ground watertight. The screens will limit the passage of water into the ground, for example during the construction of a dam.
- Sealing: this type of injection consists of fixing a metal reinforcement (bar, prestressing cable, profiled tube) to the ground under pressure to have a good tearing or loading capacity.
The grout can be composed differently according to the nature of the soil and the porosity of the ground. The majority of grouts are composed of cement or a mixture of cement and bentonite. Injection is carried out using state-of-the-art equipment. All grouting operations are preceded by drilling of the soil.
Jean-Yves Stoquer’s speciality is special foundations, a highly specialised field with its own jargon and complex techniques such as soil injection.
