CIVIL FITTING OUT AND LOGISTICAL PROCESS - The Westerschelde Tunnel: Approaching Limits - page 209

distributed the material after which vibration plates ensured systematic
compaction. The total volume of sand processed (and gravel round the
drainage pipe) amounted to approximately 185,000 m 3 .The top of the sand-
cement stabilisation was finally provided with a layer of phosphorous slag
serving as a road foundation.
Cross connections
The cross connections were constructed at some distance behind the tunnel
boring machine (also see Chapter 13 - 'Cross connections'). A range of work
took place in a restricted space, that was slightly more than half of the tun-
nel width, which also made the supply and removal of materials and equip-
ment and their transport necessary. Building the cross connections first of
all made setting up a system for the boring of the freezing pipes necessary.
Then the freezing system was put in position and the lining was fitted
with stiffening girders and thermal insulation. After the ground had been
frozen, the excavation work could be started from the other tube, but before
that a heavy emergency door was fitted. Machinery was of course required
for the excavation work in the form of a milling cutter with a weight of
approximately 15 tons. After several cubic metres of soil had been excavated,
a manoeuvrable bob-cat picked up the excavated material, transported it
to a train that took it along the main railway track to the outside. When part of
the cross connection had been excavated, a process which incidentally took
place without stopping, a layer of shotcrete was applied immediately. This
concrete and the reinforcement incorporated in it had to be - if necessary -
immediately available for the tunnel builders to use. As soon as the exterior
wall was finished, waterproof sheeting was installed. Then the interior wall
was constructed: for which reinforcement, formwork and of course the con-
crete itself also had to be supplied.
After a cross connection had been completed, and as soon as the equipment
was no longer needed, it was moved to a new location (in as far as this had
not been done already) and the whole process was started again.
Fig. 14.3
Excavation of a cross
connection