Improvements in or relating to lining elements for tunnels or shafts.

摘要

The disclosure relates to a shaft lining comprising precast concrete arcuate lining elements including a pair of special lining elements (11) to provide an access point for a horizontal tunnel. Each element (11) comprises an outer section (12) cast in high compression strength high impact strength steel reinforced concrete with a semi-circular shaped recess (13) in which a lightweight concrete wall section (14) is cast with an integral flange (15) along the diametrically extending edge thereof to abut with the corresponding flange (15) of the adjacent segment when erected. The two elements (11) are secured together by a fixing bolts (17) and (20). The lightweight concrete circular wall formed by the two semi-circular sections (14) within the elements (11) supports the wall of the encircling shaft during erection of the shaft but can readilly be broken out when connecting the shaft to a tunnel leading from the shaft.