Process and device for building a tunnel immersed on a sub-sea soil

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.