Patent ID: 7766579

Claim:
A process for building a wholly or partially immersed tunnel on a natural or artificial sub-sea soil, wherein the tunnel is built in successive tunnel sections, characterized in that a standard immersed section is built on the sub-sea soil by means of a machine suitable for operating in immersion that is moved forward in the water, on the sub-sea soil, as required, along the proposed tunnel alignment, said machine comprising a fluid-tight working space at atmospheric pressure suitable for accommodating the personnel and equipment necessary for the construction and in situ erection of the section, in that the tunnel is kept fluid-tight as it is built, in that a sufficiently large communication space is kept open between the part of tunnel already built and the working space of the machine to allow construction and erection of a new section, in that the tunnel is used, as it is being built, to transport the component parts of the sections to the machine as required, and in that the sub-sea soil is prepared by dredging a trench along the proposed alignment for erection, placing foundation material on the bottom of said trench as a foundation layer, and said machine comprising arms carrying grading tools, mounted so as to pivot forwards, backwards and laterally, grading said foundation layer, to scrape the excess thickness at the top of that layer and to the sides of that layer.