Abstract: A tunnel-excavating machine comprises an excavating head, preferably a full-cut head, adapted to excavate the full-cross-section of the tunnel to be formed, which is slideably mounted for movement relative to a pair of support frames. Means is provided to relatively displace the support frames axially and the support frames are surrounded by a blade shield made up of a multiplicity of individual blade segments, each of which can be individually advanced by hydraulic means connected to the support frames. The individual blade members, which span both frames, can be urged against the wall of the tunnel by respective fluid pressure means in each of the frames.