being able to spill out onto the ground between this and the side walls and to fill the cavity so as to encapsulate the cross-members and iron bars or other connector members for connection to the superstructure element and, after hardening, to constitute a monolithic mass which connects the foundation element and the superstructure element permanently to the ground.
This solution enables a relatively light, monolithic frame for use as a non-recoverable form to be prefabricated, the frame being transportable at little cost from the factory to the construction site and, given its lightness, being movable equally cheaply on site. The ground at the construction site intended to receive the frame needs to be only roughly flattened and levelled since the final levelling of the frame may be achievedand in that the tunnel section is made by the following operations:
the laying of two rigid monolithic frames on the ground on opposite sides of the bottom of the cutting, each with the interposition of the said adjustable support devices between the frame and the ground;
the levelling of the two frames by adjustment of their adjustable support devices;
the connection of each frame and its pier at least by means of a connecting reinforcement fixed, on the one hand, to the pier and, on the other hand, inserted in the frame;
the casting of a hardenable fluid binder material in the cavity in the frame so that this fluid material, after spreading over the ground beneath the frame, fills the cavity in the frame and encapsulates the cross-members of the