mohring engels.indd - Keramo Steinzeug

costs. It is apparent that jacking at shallow depth can be
more cost-effective, especially if valuable road topping is
encountered. The depth margins for cost-effectiveness
shown in the following sections would shift even further
and very clearly in favour of pipe jacking if for example
– dewatering were to be necessary,
– soil conditions were unfavourable and possibly complete
replacement with compactable filling soil were
necessary,
7.1
5000
4500
4000
3500
3000
2500
2000
1500
1000
DM/m
500
2,95 m - DN 200
3,80 m - DN 250
0
Berlin 1997
0 1,75 3,00 4,00 5,00 6,00
Open construction
Micro-tunnelling
4,40 m - DN 300
Micro-tunnelling Page 25
– prior re-laying of lines and/or measures to secure
structures, pipelines or other installations in the slope
area of open trenches were required,
– manual digging of pits were necessary,
– local conditions made elaborate trench sheeting indispensable,
– traffic diversions, traffic lights etc. were ordered as
supplementary measures in open construction.
Sewer-construction costs compared above the water table
open construction / micro-tunnelling using vitrified-clay pipes
Surface unpaved
5,20 m - DN 800
6,00 m - DN 600
Depth in meters
DN-200 DN-250 DN-300 DN-400 DN-500 DN-600 DN-800
Sewer-construction costs compared; surface unpaved
Where the surface is unpaved, jacking for
DN 200 at depths > approx. 2,95 metres
DN 250 > approx. 3,80 metres
DN 300 > approx. 4,40 metres
DN 600 > approx. 6,00 metres
DN 800 > approx. 5,20 metres
is more cost-effective than open laying. That the intersection
of cost-effectiveness is not reached for
nominal sizes DN 400 and DN 500 in the depth range
up to 6.0 metres considered is due to the high cost
shares for the starting and target shafts. For DN 400
the bore changes from 2.00 to 3.00 metres, so that at
depths of 5.00 metres the shares in total costs for
starting and target shafts are for example 29% /
26%.
Fig. 28