Drive shields for tunnelling

摘要

A drive shield for use in a tunnel driving operation has an inner frame with hollow rings interconnected in a rigid fashion. A plurality of sharp-ended drive members combine to form a cylindrical shell contacting the tunnel wall. Rams serve to advance the drive members in the advancing direction either individually or in groups and to draw up the inner frame. Support devices of circuate shape form a second shell inside the drive members and support and guide the latter. Piston and cylinder units are interposed between the rings and the support devices and serve to displace the latter radially so that selected members can be forced against the tunnel wall with a greater or lesser pressure.