Civil Engineering Reference
In-Depth Information
lying on top at the maximum gradient. Due to the higher positioning, the tun-
nel cross section crosses the border layer between the Boom clay and the sand
lying above on the northern side of Everingen over a long distance. Under the
southern side of the Everingen, the positioning of the alignment is deter-
mined by the presence of loosely compacted sand. In this a larger soil cov-
ering is maintained. Also, due to the longer alignment which is the result of
this, the riprap discovered on the foreshore of Zuid-Beveland has been
avoided. From the deepest point under Everingen with the road surface at
approximately 47.50 metres
NAP and the underside of the tunnel at approxi-
mately 51.25 metres
NAP, this has resulted in a gradient of approximately
1% which turns into a maximum gradient of 4.5% until the highest point is
achieved at Zuid-Beveland (the dyke surrounding the access ramp).
By applying a permanent soil fill at the surface level above the tunnel - with
the usage of the surrounding dykes - the bored tunnel could be ended as
high as possible. The depth positioning of the access ramps have therefore
remained limited.
The cross section
The tunnel is carried out as a motorway and consists of twin parallel tubes
across the entire length, having two driving lanes of 3.50 metres with a redress
lane of 0.70 metres and safety barriers in each tube. In the open section of the
access ramps up to the passing of the surrounding dyke, a reservation has
been made for a so-called overtaking lane which was easy to fit in due to the
distance between the tunnel tubes which was necessary for the boring process.
Cross section of the
tunnel with cross
connection
Fig. 3.5
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 boring diameter of the tubes measures 11.30 metres, whereas the inter-
nal diameter is 10.10 metres. Both tubes are positioned spaced 12 metres
apart which is approximately the boring diameter. Due to this, there was no
question of influences between each other during the boring process. In
order to limit the width of the access ramps, here the distance at the ending
of the tubes was reduced to approximately 7 metres. Every 250 metres the
tunnel tubes are connected by cross connections which serve as an escape
route in cases of disaster. Originally the cross connections were spread 500
metres apart based on a probabilistic safety approach.This distance was later
reduced to 250 metres based on a deterministic approach (see
Chapter 4).
The cross connections also make it possible for emergency services to reach
the location of an accident via the non-incident tube. The design and the
implementation of the cross connections are described in more detail in
Chapter 13.
The section under the road surface, as part of the boring process, was filled
with a package of stabilised sand. A drainage tube at the bottom of the tunnel
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