In the Dutch highway A12, near Ede, a new tunnel structure crossing the existing highway was designed and built. This structure is commonly referred to as ODG A12 and provides the underpass junction for the Parklaan and hence an improved accessibility of the city of Ede. The structure consists of several tunnel segments. The largest segment, which provides the actual crossing, was prefabricated on-site and then was placed at its final destination in just one weekend.
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Tunnel under-
neath highway
A12 near Ede
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The structural design, construction and placement of an on-site
prefabricated tunnel segment within strict conditions
In the Dutch highway A12, near Ede, a new tunnel structure crossing the existing
highway was designed and built. This structure is commonly referred to as ODG A12 and
provides the underpass junction for the Parklaan and hence an improved accessibility of
the city of Ede. The structure consists of several tunnel segments. The largest segment,
which provides the actual crossing, was prefabricated on-site and then was placed at its
final destination in just one weekend.
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Tunnel underneath highway A12 near Ede 3 2017
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ODG A12 is part of a metamorphosis of the highway section
Veenendaal - Ede - Grijsoord. The highway was upgraded with
additional fast lanes as well as several new structures such as
bridges and viaducts, allowing an appropriate connection with
the adjacent junctions (Grijsoord and Waterberg). Primary
objectives for this upgrade were an increased traffic flow and
improved traffic safety. In order to realize this upgrade existing
structures needed to be modified (e.g. widening of bridges) and
sound barriers were placed. Also the use of special asphalt
mixtures exhibiting low sound emission properties contributed
to a sustainable design solution.
The design of the new structure ODG A12 had to meet a variety
of conditions, amongst others architectural requirements and
limitation of traffic hindrance during construction and nuisance
for the inhabitants and surrounding environment. In this respect
it was chosen to apply a sliding operation of the full monolithic
structure in order to limit hinder and maintain an operational
highway as long as possible. Due to its geometry (15 m wide, 80
m long and approximately 6 m in height) this was a challenge.
The structural calculation models incorporate all subsequent
stages of the building process and associated loads, as well as
different soil parameters. The section dimensions were opti-
mized to limit the dead weight to approximately 3800 tons.
Within the models, soil pressures underneath the structures
during the building sequence were carefully monitored in order
to limit settlements.
Structural design and design considerations
The main design aspects that had to be taken into account, are:
- the tunnel crosses the highway at an angle of 33?. This means
that the tunnel segment length is large compared to the width
of the highway (width of the highway is approx. 36 m, length
of the tunnel segment is approx. 80 m);
- the road design for the tunnel is horizontally curved. In order
to optimize driving comfort as well as material usage, it was
chosen to adopt the same curvature for the complete length
of the tunnel. This results in a constant cross section of the
tunnel segments;
- soil parameters showed that a shallow foundation was possible;
- essential within this project was to limit traffic hindrance to an absolute minimum. This resulted in an additional require-
ment in terms of construction technology and intended
building phases;
- the aesthetical appearance was mandatory and was derived
from the aesthetical vision 'Regenboogroute A12', setting an
extensive list of requirements. Masonry appearance of the
structure was mandatory. At the inner side a finishing
consisting of tiles and light armatures was required. The entire structure is made of reinforced concrete (without
prestressing). The strength class of the concrete used was
C45/55. Figure 3 shows a typical cross-section.
The structure was modelled in Autodesk Revit. In close coop-
eration with the architects, solutions were designed to satisfy
the aesthetical vision. Visuals were created, based on the Revit
model, which have been used in several stages of the project,
such as requesting the building permit and during meetings
with inhabitants.
Figure 4 and photo 5 show an architects impression and a
photo taken from approximately the same viewpoint.
ing. Stefan Schoenmakers MSEng,
ing. Erik de Rooij PMSE
Wagemaker
1
View on the monolithic, on-site prefabricated tunnel segment from the aircredits photos: Rijkswaterstaat2 The tunnel segment during the sliding operation
3 Typical cross section
2
3
Tunnel underneath highway A12 near Ede 3 2017
Tunnel underneath highway A12 near Ede 3 2017 50
open segmen t closed segmen
t
dumping lane closed segment
(precast and moved)
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at the crossing location, the existing road has been demolished
and a new road has been built within this time span.
In the preliminary stages other design solutions, such as the use
of (prestressed) concrete slabs combined with temporarily
structures (e.g. sheet piles), have been considered. However, all
alternatives appeared to be less preferable than the monolithic
structure, as now built.
It was decided to apply a sliding operation to move the tunnel
segment to its final position. Performing a sliding operation
involves the use of hydraulic jacks to lift the structure. To allow
for the local jack loads, dowels were cast in with associated local
reinforcement. Due to the horizontal curvature, the sliding oper -
ation was non-conventional. Since sliding was the preferred
displacement technique, the total amount of dead weight should
be limited. In the design of the concrete dimensions (e.g. wall Construction phases and relation with
structural design
In order to minimize traffic hindrance it was chosen to adopt
the following building schedule:
- Building of one tunnel segment at the final position;
- Prefabrication of the major part of the tunnel on-site at a
temporarily position;
- Sliding of the prefabricate segment towards its final position;
- Building open tunnel segment.
In figure 6, a plan view of the complete structure is given.
In adopting this building sequence, the highway A12 could
remain operational during the entire construction time (photo 1)
with the exception of just one weekend. During this weekend
tons of earth have been moved to create an opening in the soil
body providing the space needed to position the tunnel. Also,
4 Architectural impression
5 Built situation (under
construction)
6 Plan view of the complete
structure
7 3D-model of combined
tunnel loaded by a
tandem axle load
8 Distribution of principle
moment m
1 [kNm/m 1];
(a) interior; (b) exterior
4
5
8a 8b
7
6
closed segment
(precast and moved) closed segment
(cast in situ)
dumping lane
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Figure 7 shows an impression of the shell model consisting of
both tunnel segments. In between both segments a dumping
lane of 2.5 m in width is used.
The building sequence is explicitly taken into account in the
models. Based on the results in governing cross sections, amounts
of necessary reinforcements are calculated taking into account
both ULS and SLS. Within the models, occurring soil pressures
underneath the structures during the building sequence were
carefully monitored in order to limit settlements. Soil pressures of
approximately 250 kN/m
2 were considered allowable.
Figure 8a and 8b show the distribution of the first principle
moment in SLS-load combinations. The dumping lane allows
for initial settlements of both segments without involving
undesirable forces.
A special aspect within this project was the local load on the
tunnel walls introduced due to the presence of the hydraulic
jacks necessary for sliding. The sliding operation consist of
several stages. First, the tunnel segment was lifted initially to
obtain clearance between the bottom side of the floor and soil.
These jacks are mounted on the steel sliding frame. All dead
weight is transferred at the location of the dowels. Figure 11
indicates an impression of the 3D-Allplan model of the rein-
forcement at this dowel location. Additional reinforcement to
prevent breakout is indicated as well. Since lots of jacks were
present, the load per jack was relatively low and hence, only a
few bars were necessary.
Project specifications / resumé
Heijmans acted as contractor to build this project but is also
responsible for the maintenance over a period of 16 years. Wage-
maker, in commission of Heijmans, was the structural engineer.
The project was started in 2014 with the preliminary stages and
has been completed in October 2016.
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thicknesses, slab depths) this was taken into consideration at all
times. It was chosen to adopt a phased casting sequence for the
middle part of the floor slab since during the sliding operation
the structure was loaded only by the dead weight. After position-
ing the tunnel segment, the final thickness of the floor slab was
created by the second cast. The connection was realized by rein-
forcement at the interface. Soil compaction allows the ground
underneath the floor to be fully mobilized.
Photo 1, 2, 9 and 10 show impressions of the sliding operation.
Calculation method
The structure was modelled in 3D SCIA Engineer. In total
three models have been used:
- a shell model of the first tunnel segment (built at its final
position);
- a shell model of the monolithic segment to be slided to its
final position;
- combined model of the both closed tunnel segments at the
final position.
9 View on the sliding
tunnel segment from the
side
10 Detail of jacks and sliding
girders
11 3D reinforcement model
(only one dowel is
drawn)
9 10
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Tunnel underneath highway A12 near Ede 3 2017
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