CROSS CONNECTIONS - The Westerschelde Tunnel: Approaching Limits - page 190

then, was not measured by the 'Frost Heave' tests. However, this expansion
was indeed normative for the deformation of the tunnel tubes.
The absence of reliable values meant that assumptions regarding the degree
of expansion were not sufficiently substantiated, whereas this was essential
for a proper calculation. Due to the fact that the most unfavourable assump-
tion for the expansion would mean that the main tunnel tubes would reach a
failure stage, the commissioning party decided on a closer investigation.
This investigation consisted of two parallel tracks: a laboratory research
into the degree of expansion parallel to the cross connection and a three-
dimensional analysis with a finite element model 'DIANA'. This latter inves-
tigation was geared towards the stress development in the tunnel tube at
the position of the cross connection, in which the degree of expansion was
varied. In this 3D analysis, the tunnel was modelled at both sides of the
cross connection across 14 rings ( 28 metres) in order to be able to observe

the effects longitudinally.

Expansion of the
frozen soil

Fig. 13.7

12 m

Fig. 13.8
3-D picture of possible
deformation of tunnel
tube at the position of
the frozen soil

Model : Fases Del - 135
LC1 : Load case 1
Step : Load : 1
Model TDTX… O RESTDT
Max/min on results net:
Max - 110
Min - 247 10 4

Y

X
Z

From the laboratory research it was evident that during the freezing of
Boom clay, expansions could possibly occur measuring at least 16 mm par-
allel to the frozen soil at the location of the tunnel tube. For sandy layers,
hardly any deformations were expected: water expands and freezes and at
the same time it pushes the water that is still present in the surrounding