Civil Engineering Reference
In-Depth Information
depth (the boring machine was situated at approximately 45 metres
NAP)
made the use of diaphragm walls very susceptible for inaccuracies. Also the
use of boring piles at that depth in the hard clay was considered as risky and
the fact that on applying the freezing technique, the freezing-pipes would
have to be withdrawn again (to be able to continue boring), met with objec-
tions. Working from a working island therefore did not appear to be an option.
Cutting wheel covered with foil - a simple but brilliant idea
In the further search for solutions, attention was again entirely concentrated
on the subgrade. The basic idea which was presented, consisted of the cut-
ting wheel boring forwards over a distance of 0.4 metres and then with-
drawing the cutting wheel again into its original position. Then the entire
space between the pressure wall and the Boom clay - which also contained
Fig. 11.24
(a) Spanning the foil
over the cutting wheel
(b) Creating the
atmospheric
circumstances for the
repairs of the main
bearing seal
1. Pull in through the opening
3. Spanning to the top
5. Unfold downwards
3
2. Positioning of belts
4. Spanning the top half
6. Spanning across the
whole surface
12
11
1
10
2
9
3
8
4
5
7
(a)
6
Phase 3
Phase 2
Mortar
Air
cushion
Phase 1
Clay stratum
Compressed
air
Cutting wheel
Bentonite
suspension
Pressure wall
Pressure wall
hatch
400 mm
400 mm
200 mm
Phase 4
Phase 5
Atmospherical
Bentonite
suspension
Main bearing seal
Disk of mortar
(b)
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