BBA Pumps Underwater Excavation and Construction Video
The presence of water is ussualy considered a nuisance in construction, particularly when excavating removing water is common practice. In some cases however, water can be a very useful tool that may simplify things greatly.
With the “flooded excavation principle”, the construction site is flooded after the retaining walls have been installed (e.g. sheet pile). When the excavation is in layered soils facing artesian pressure and confining layers, the weight of the water compensates for the topsoil being removed and prevents failure of the base of the excavation. Particularly when it is difficult to install pump systems, or when reducing the artesian pressure is impossible or undesirable due to other factors, the flooded excavation may be the easiest option.
Rather than with earthmoving equipment, the actual digging is done with a submersible pump that is suspended from an excavator or crane. By installing jetting nozzles on the submersible pump the soil is agitated, creating a slurry that can be pumped away, thereby digging out the soil. When the intended depth is reached, underwater concrete is poured to create a watertight base that will create a caisson in combination with the retaining walls already installed.