Tunnelling

Abstract

The invention is concerned with a method of constructing a lined tunnel using a tunnelling shield having a tall skin and in which the tunnel lining is of the expanded type comprising a number of ring sections 4 fitted together end to end and in which each ring section 4 is formed from a number of arcuate segments 5 which are fitted together circumferentially and which are expanded radially into contact with the surrounding ground 1. The expansion may be effected by means of one or more wedges which are driven between pairs of the segments, or by jacks which are expanded between segments. In the method each ring section 4 of the tunnel lining is erected by first assembling its segments 5 to form the new ring section 4a in an unexpanded state within the tail skin 2 of the tunnelling shield while a thin rear extension 3 of the tail skin 2 overlaps the leading end of the previously erected and fully expanded ring section 4b and whereby an annular layer of resilient compressible material 6 is located around the newly assembled ring section 4a, the annular layer of resilient compressible material 6 being formed by layers of the material attached to the outer surfaces of the individual segments 5. The newly assembled ring section 4a is then pushed against the leading end face of the previously erected ring section 4b and is partially expanded so that the layer of compressible material 6 is partially compressed against the inside of the tail skin 2 and its extension 3 as shown. The tunnelling shield is then advanced until its thin rear extension 3 overlaps the leading end of the new ring section 4a, and the new ring section 4a is then further expanded until it reaches its fully expanded condition.

Dependencies are inferred from the claim text.