Shield heading tubbing supports - ring unit has closure tubbings half ring width to join remaining tubbings

摘要

Tubbing for supporting shield headings or tunnels forms axially connected rings made up from several reinforced concrete tubbing elements which are tongued and grooved together, each two tubbings being bevelled at the ends crossways to close up the respective ring. Each ring contains one tubbing serving as closure member which consists of two tubbings each half the width of the ring. These two tubbings have connection surfaces arranged axially with respect to the ring so as to meet up with suitably bevelled surfaces provided on the adjoining tubbing elements. The bevelled surfaces on the closure tubbings themselves are similarly tongue and grooved to the remainder, and the two surfaces of these two tubbings facing each other in the form of parts of the ring are also joined by tongue and grooving.