Ja. Richards et al., DESIGN AND CONSTRUCTION OF A SEGMENTAL LINING FOR A MACHINE-BORED TUNNEL - DELIVERY TUNNEL NORTH, LESOTHO-HIGHLANDS-WATER-PROJECT, Tunnelling and underground space technology, 9(1), 1994, pp. 91-99
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Categorie Soggetti
Engineering, Civil","Construcion & Building Technology
The 21-km-long Delivery Tunnel North for the Lesotho Highlands Water P
roject is split into true main tunnel drives of 8 km and 11 km lengths
. The tunnel is located in the sedimentary rocks of the upper Karoo se
ries with cover of up to 350 m. The rock units comprise claystones, si
ltstones and sandstones. In the poorer geology, early support of the t
unnel periphery is essential. The method of tunnel construction involv
es excavation by a TBM and the simultaneous erection of a precast conc
rete segmental lining that provides both rock support and a final tunn
el lining. The segmental lining is designed and constructed as part of
an integrated excavation/support/lining system. There are three types
of segments, differentiated by the amount of steel reinforcement. The
distribution of the different segment types along the tunnel, relativ
e to the geological conditions and depth of cover will be optimized by
monitoring of the performance of the lining during the construction p
eriod.