Driving shield machines are known in the construction of tunnels through unconsolidated rock; in these known machines, the working face is shored up by supporting fluid in a working chamber of the driving shield machine sealed off from the tunnel. With these known driving shield machines, unconsolidated rock can fall out of control into the entire working chamber if the working face collapses during the tunnelling process and thus seriously jeopardize the safety of men working in the tunnel. To reduce this risk considerably, the driving shield machine according to the invention is provided with a partition (40) which can slide longitudinally and divides the working chamber (3) into two partial chambers (3', 3''). An aperture (52) is provided in the partition (40) and a tunnelling arm (10) extends through the aperture, which is designed so as not to restrict the mobility of the tunnelling arm (10). Since the partition can slide into a position adjacent to the working face, the latter can be given additional mechanical support if a collapse seems likely, without any need to interrupt the tunnelling process and provide support using the support fluid.