Abstract: The invention relates to a boring machine for digging tunnels in a wide variety of qualities of ground, of the type comprising a first front shield, containing the boring head, and the members for driving the same, and a second shield, fitted with posts or "grippers" for providing the anchorage necessary for the advancement of the boring machine, in which a third shield is provided, arranged between said first and said second shield, such that the first shield overlaps partly with it and is able to slide axially with respect to the third shield itself and that the assembly first shield/third shield is able to vary its advancing direction with respect to the second shield; guide means being provided between said first and said third shield, which guide means allow these latter to perform a relative movement in the longitudinal axial direction only, and means being provided for advancing said first shield with respect to said third sh shield, as well as means for setting at an angle the assembly first shield/th

Abstract: A machine for mechanical tunnel boring, of the rotating cutter head type, comprising a grid rigid with the cutter head, parallel to the theoretical boring surface, provided with a set of void spaces wherefrom the cutting tools slightly project, said void spaces having a size corresponding to the optimum dimensions of the fragment of mined material.

Abstract: Front and rear shields are telescopically joined together. The front shield carries a power driven rotary cutterhead means. Main thrust rams are provided between the two shields for pushing the forward shield forwardly relative to the rear shield while the cutterhead means is being operated to mine the tunnel face, and also to pull the rear shield forwardly relative to the front shield. The rear shield includes a gripper assembly for reacting thrust and torque and a plurality of groups of auxiliary thrust rams which extend rearwardly from the rear shield to contact forward end portions of a tunnel lining which is erected under cover of a tail section of the rear shield. The auxiliary thrust rams are extendable a distance that is at least slightly larger than the axial length of one ring of tunnel lining segments. The main thrust rams are extendable a distance that is slightly larger than 1x of the stroke of the auxiliary thrust rams, where x is the number of groups of auxiliary thrust rams.