GEOCISA is the only company in Spain to use this technique. In very open ground, such as in rock fills often used in marine works, bentonite slurry levels cannot be maintained due to the high permeability of the ground. In these cases, GEOCISA carries out a self-hardening slurry trench wall prior to the construction of the RC diaphragm wall. Afterwards, once the slurry has set and hardened, the RC diaphragm wall is constructed within the hardened slurry trench wall.
When needed, a hardening catalyst is added to the slurry mix. Voids in the ground are sealed off with the hardened slurry, so that when the RC diaphragm wall is being built, the bentonite slurry level can be kept above groundwater level, holding up the panel sides during excavation and allowing the panel to be dug to depth. The preparatory slurry trench wall is normally built with greater a thickness that the reinforced concrete diaphragm wall.
GEOCISA has used this technique in many projects where diaphragm walling would not otherwise have been possible, such as when having to dig through rock fill in ports; landfill sites; or where the fines in manmade fills have been washed out by groundwater seepage. GEOCISA has also successfully used this technique to protect RC diaphragm walls from highly aggressive environments.
Some examples of works of this kind include the “Atraque del Rey” or “King’s Berth” at the Porto Pi naval base in Menorca, the “Tenerife Coast Road Underpass”, and the “Underpass between intersections at Port of Valencia”.