the rock bolts can be drilled into place directly through the openings in the shield it is possible to use support plates on the rock bolts within the pockets between the t shaped members as these plates emerge from the shield 15 the rock bolts can be tightened to pull the support plates up into contact with the roof the roof is continuously supported and there is no opportunity for sections of the formation to pull away from the roof once the tunneling machine 10 enters an area where the roof 22 of the tunnel must be supported by lagging sections of lagging may be moved into place entirely within the protection of the shield 15 the thrust cylinders 36 and 37 maintain the shield 15 in a position proximate the formations loose rock is prevented from falling onto the tunneling machine 10 and endangering personnel in the area ring beams are positioned in the tunnel 11 and as the tunneling machine 10 advances forward sections of lagging may be moved into place on the ring beams wedges may then be driven between the lagging and the ring beams to force the lagging into contact with the roof or the lagging locked in place in some other fashion the roof of the tunnel may be lagged with sections of lagging immediately adjacent each other or spaces may be left between lagging depending on the nature of the support required the present invention provides continuous support to the formations uninterrupted by gaps that would create a danger zone where loose rock could fall into the tunnel the formations.