ABSTRACT
There are so many factors, apart from design considerations, which influence the cost of tunnelling that it is only possible to give guide prices for a sample of the work involved. For more reliable estimates it is advisable to seek the advice of a Specialist Contractor. The main cost considerations are:
* the nature of the ground * size of tunnel * length of drive * depth below surface * anticipated overbreak * support of face and roof of tunnel (rock bolting etc.)
* necessity for pre-grouting * ventilation * presence of water * use of compressed air working
The following rates for mass concrete work cast in primary and secondary linings to tunnels and access shafts are based on a 5.0m depth of shaft and 15.0m head of tunnel Apply the following factors for differing depths and lengths:
HEAD LENGTH: 15m 30m 60m 90m Shaft depth 5m +0% +10% +20% +32½% Shaft depth 10m +5% +12½% +27½% +35% Shaft depth 15m +10% +17½% +32½% +40% Shaft depth 20m +15% +20% +37½% +42½%
EXCAVATION Excavating tunnels in rock
1.5m diameter – – – – m3 528.00 3.0m diameter – – – – m3 330.00
Excavating tunnels in soft material 1.5m diameter – – – – m3 250.25 3.0m diameter – – – – m3 137.50
Excavating shafts in rock 3.0m diameter – – – – m3 203.50 4.5m diameter – – – – m3 170.50
Excavating shafts in soft material 3.0m diameter – – – – m3 118.25 4.5m diameter – – – – m3 101.75
Excavating other cavities in rock 1.5m diameter – – – – m3 528.00 3.0m diameter – – – – m3 330.00
Excavating other cavities in soft material 1.5m diameter – – – – m3 250.25 3.0m diameter – – – – m3 137.50
Excavated surfaces in rock – – – – m2 19.25 Excavated surfaces in soft material – – – – m2 19.25
hours £ £ £ rate £
IN SITU LINING TO TUNNELS
Notes The following rates for mass concrete work cast in primary and secondary linings to tunnels and access shafts are based on a 5.0m depth of shaft and 15.0m head of tunnel. See above for additions for differing shaft depths and tunnel lengths.
