CROSS CONNECTIONS - The Westerschelde Tunnel: Approaching Limits - page 185

Pas van Terneuzen

Everingen

Z1

0 0

K1 K1

KZ1

KZ1

Z1 Z1

10 m

10 m

KZ1

Z1

Z1

26

1

ZK1

20 m 20 m

ZK1

BK1

25

BK1

2

Z1

30 m 30 m

Cross connection

BK2

9 10 11

12 24

8

13

14

3 15

40 m 40 m BK2

7 16 23

17

18

22

19 20

21

GZ1

GZ2

6

50 m

4

50 m

BK2 5

BK1

60 m 60 m

K2 GZ2

BK2

70 m 70 m

approx. 6,600 m

take place within the protection of this frozen soil. On the one hand the oval-
shaped ring had to retain the ground water during the whole construction
phase, and on the other hand it had to (temporarily) take up the prevailing
ground and water pressures.
Of a total of 26 cross connections, 9 are positioned in moderately firm to
firm sand, 11 in the Boom clay and 6 in a mixed subgrade. Although the
Boom clay is poorly permeable, here the choice was also taken to apply the
freezing technology because of the possible presence of aquiferous sand
lenses and vertical cracks. The water pressure to be restrained varies from
2 to 6 bar.

Fig. 13.1
Location of the cross
connections

Fig. 13.2
Cross section of tunnel
tubes with cross
connection

Section in the area of a cross connection

11.33 m

10.10 m

Segmental lining, t 45 cm

approx. 12 m

Cross connection, every 250 m
Steel segment Cable trench

Installation basement

Cable gallery

The design

The inner lining of the cross connection consists of an oval-shaped circle
made of reinforced concrete 0.4 metres thick. This is enclosed by the outer
lining of reinforced shotcrete which is 0.35 metres thick. The required struc-
ture gauge of 1.5 by 2.1 metres was determinative for the internal measure-
ments: the 'rings' are 2.5 metres wide and 2.75 metres high.The connection
of the (oval-shaped) central section of a cross connection on the wall of the
bored tunnel tubes consists of a concrete collar structure. A steel plate in the
pouring joint in combination with a rubber seal and otherwise filled with a
grout mixture, ensures there is a watertight connection between the tunnel
tube and collar structure.The collar structure ensures that adequate space is
created for this connection.
Another function is the taking care of the transmission of the bearing
forces between the tunnel tube and cross connection, while it is possible to
take up the construction tolerances of the tunnel tube as well as the cross