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Gallery Ravensburg, B30n

1. Task definition

The federal highway B30 runs from the Danube to Lake Constance and connects the central cities of Ulm on the Danube and Friedrichshafen on Lake Constance over a length of about 100 km. Between Weingarten and Ravensburg it is overlapped by the B 32, which runs from Hechingen via Ravensburg to the Bavarian Allgäu. This north-south connection, which was already heavily frequented in the Middle Ages, increasingly developed in the 20th century into the main route of the Swabian Oberland, which not only serves to handle freight traffic, but has also acquired special significance for recreational traffic from the conurbations to the Lake Constance area and the Alps.

The traffic load is correspondingly considerable, with over 60,000 motor vehicles/day in the Ravensburg urban area today.

As a consequence, unacceptable traffic conditions for residents and motorists due to noise, exhaust fumes and traffic jams have arisen in recent years, which is why the construction of a bypass between Baindt and Ravensburg to relieve the local thoroughfares and improve traffic safety became a particularly urgent priority.

In view of the considerable scope, the overall measure in the Baindt and Ravensburg area was divided into 6 construction phases. The first construction phase was started as early as 1981. In the spring of 1989, the noise protection calculations were revised, thus creating the basis for the supplementary zoning decision, which included in particular the commitment of the road construction administration to hold a competition for the replacement of noise barriers by planted noise protection systems.

The design of the noise protection systems was the task of a working group within the administration, which suggested that the Ravensburg/North - Ravensburg/South construction section (construction section V) be provided as a model case for a design competition with integration of the noise protection systems into the surrounding urban landscape.

Four private planning teams developed proposed solutions in the spring of 1990. The jury, which consisted of senior staff from the road construction administration, the state building construction administration and the city of Ravensburg, ultimately decided in favor of the proposal for a generous filling of the site along the western slope on the Schüssen in conjunction with retaining walls, galleries and a tunnel in the area of the intersecting Meersburger Strasse.

The jury considered the noise protection tasks to be fulfilled in this way in an environmentally compatible and landscape-friendly manner and also adopted the red diagonal tubular steel supports provided for in the proposed solution as an aesthetically satisfactory feature typical of the "Ravensburg Gallery".

2. Design of the structure

2.1 Tunnel structure (BW 21)

Because of the very oblique crossing of Meersburger Straße and due to the noise protection calculations, a tunnel structure as a green bridge of 230.85 m length was required between the northern and southern gallery.

2.1.1 Subsoil and groundwater conditions

The construction section V of the new B 30 runs in the area of the tunnel and the gallery structures on the western edge of the Schussental plain in the transition area to the valley flank. The terrain is characterized at the foot of the valley flank by slope spring bogs and in the valley plain as waterlogged floodplain meadows.

About 10,000 years ago, at the end of the last foreland glaciation, the Schussental was filled by a glacier tongue of the great Rhine glacier. The ice stream melted a trough-like hollow shape into the sandstone and marl formations of the upper freshwater molasse, which is filled from bottom to top with basin sand, basin clay and blowdown masses rising towards the slope. Towards the top, this layer package is overlain by two post-glacial layers, namely the talc deposited by the gunning and the flood formations of the floodplain.

The talc represents an aquifer spread over the entire valley plain. At depth, another aquifer follows in the area of the basin sand, whose deep groundwater emerges via the blowdown masses on the valley flanks and also passes into the talc underground.

Due to their unstable grain structure and their pressure water conduction, the slurry masses on the valley flank, which served as the foundation horizon for the tunnel, proved to be an extremely difficult subsoil, which required special measures for both the foundation and the building structure.

2.1.2 Foundation

The design envisaged the construction of the structure in the shelter of a temporary, back-anchored excavation pit shoring enclosing the entire excavation pit. Groundwater drawdown and relief via deep wells was provided to stabilize the soil strata. The tunnel is shallowly founded on the existing basin clay layers and slurry. Unsuitable soil masses will be replaced. A 50 cm thick gravel filter layer will be placed on the existing soil.

2.1.3 Construction and concrete technology

Due to the strong inhomogeneity of the ground, the tunnel was designed as a jointless structure along its entire length. The different ground conditions were taken into account by varying the subgrade reaction modulus in the longitudinal and transverse directions.

A concrete technology report was prepared for the planned jointless construction of the tunnel and galleries.

For the watertight structural concrete of concrete strength class B 35 with a crack width limitation to W < 0.15 - 0.20 mm, the expert opinion required low heat generation, low shrinkage deformations and the smallest possible temperature expansion.

The most important concrete technology specifications are:

  • Fresh concrete consistency KR
  • 300 kg/m3 PZ 35 L NW-HS
  • 70 kg/m3 Fly ash
  • 145 kg/m3 Water (w/c = 0.48)
  • 3.5 ml/kgC Concrete plasticizer
  • 20 ml/kgZ Superplasticizer
  • 1,956 kg/m3 Aggregate
  • Fresh concrete temperature > 20° C.

As structural measures, the design called for a minimum longitudinal reinforcement of 20.1 cm2/m in foundations and base slab and 11.3 cm2/m in walls and slab with a bar spacing of a = 10 cm and small concreting sections of maximum 10 m length.

The tender also provided for an extensive curing program with a curing period of at least 8 days.

2.1.4 Cross section

The cross-section is designed as a two-line tunnel tube with a system support width of 2 x 12.25 m and a clear structural height of 5.35 and 5.40 m, respectively.

The clear structural width in each tube is 11.6 m with 9.30 m of carriageway and two emergency walkways of 1.10 m and 1.20 m respectively.

The carriageway construction is carried out in the area of the tunnel structure as on the free section and is composed of:

free section and gallery:

  • 4.0 cm Stone Mastic 0/11 S mm
  • 8,0 cm asphalt binder 0/16 S mm
  • 10,0 cm Bitum. Base course
  • 20,0 cm gravel base course
  • 20,0 cm frost protection layer (i.M.)


  • 4.0 cm asphalt concrete 0/11 S PmB and light-colored chippings
  • 4.0 cm Stone mastic 0/11 mm
  • 1.0 cm sealing 2 layers bitum. Waterproofing membrane on concrete seal.

The tunnel ceiling consists of precast concrete elements in connection with an in-situ concrete slab. In the area of the crossing Meersburger Straße (L 288), the deck is designed for bridge class 60/30 (DIN 1072) and MLC 50/ 50-100 and heavy vehicle p = 2320 KN.

The entire structure is slackly reinforced. The top of the tunnel slab is sealed with a single-layer bituminous membrane and secured with 10 cm of protective concrete, as well as a drainage mat (3.5 cm).

The surfaces in contact with the ground are provided with a protective coating in accordance with "DICHT 12" and a drainage mat, behind which a gravel filter layer (16/32) is arranged towards the ground.

Between the tunnel and the galleries, space joints with joint tapes were provided in the ceiling and walls, and watertight transition structures were provided in the floor.

2.2 Northern and southern galleries (BW 20 a + 20 b)

2.2.1 Subsoil and groundwater conditions

In the area of the galleries, the same ground and groundwater conditions were encountered as in the tunnel area.

2.2.2 Foundation

The gallery is founded shallowly on strip footings under the western, solid end wall and under the eastern truss wall. In the area of the northern gallery, which is considerably longer (599.40 m), vibro-tamping has been carried out in a grid of 1.50 - 2.00 m in the entire carriageway area as ground improvement. The diameter of the tamping column is 0.80 m. For reasons of construction progress (simultaneous construction of the tunnel and the northern gallery), soil replacement was carried out as ground improvement for the considerably shorter gallery (75.60 m), so that it was not necessary to move the heavy vibro-tamping equipment.

Above the soil improvement, a 0/56 gravel sand cushion with a thickness of 0.52 m was provided as the immediate foundation horizon.

In the area of the northern gallery, two footpath and cycle path overpasses (BW 19 a and BW 20) are monolithically connected to the gallery deck.

Their abutments and piers in the floodplain are founded on drilled piles. The suspension cables of the overpasses, which are routed over a pylon located on the gallery, are anchored to the earth-side gallery wall in reinforced concrete ribs.

2.2.3 Construction and concrete technology

The galleries are constructed as an open frame structure. The frame stem on the slope side consists of a 70 cm thick solid reinforced concrete wall. The valley side frame stem is designed as a composite column row, which is guided exactly in the axis of the B 30.

The composite column rows have a V-shaped bracing that is flexurally rigidly connected to the strip footings, while the gallery cover is supported on the composite column row via concrete joints.

The composite tubes are made of St 37.3 (406.4 x 16 in the approx. 1.2 m high footing area, 406.4 x 8 in the remaining shaft area) and are filled with B 35.

The construction of the cover as a composite structure between precast reinforced concrete elements and in-situ concrete slab corresponds to that of the tunnel ceiling.

For the construction of the gallery, the same concrete technology measures had to be taken as for the tunnel, since the design also envisaged a jointless construction method in the longitudinal direction.

For the approx. 600 m long southern gallery, two expansion joints were provided, which correspond in design to the connection of the gallery to the tunnel.

2.3 Drainage and technical equipment

The tunnel and galleries are drained via longitudinal and transverse pipes. The structures are equipped with lighting systems and electrical systems for maintenance and operation.

Fences for fall protection are provided at transitions to the site and in the tunnel portal areas.

Caps and cornices will receive surface hydrophobic coating. The support base will be coated, and the steel supports will be hot-dip galvanized and coated.

3. Construction

Since the tendered design did not allow for any special designs, the execution corresponded to the specified design in all respects. The execution documents were also provided by the client in view of the special nature of the structure. The tunnel and galleries were constructed in 10.80 m long cycles. One week was needed to complete one cycle.

3.1 Gallery

The auxiliary scaffolds required for the construction of a gallery section for the assembly of the composite columns, the formwork of the slope-side gallery wall and the support of the precast floor slabs were kept in stock in triplicate in order to be able to keep to the planned weekly cycle in view of the long curing times required.

The concreting work was carried out in 5 cycles, viz.

  •  Foundations, both sides
  •  Wall, slope side
  •  Column base, downhill side
  •  Column backfill

In-situ concrete for the slab

The four steel tubes for the composite columns of each section were adjusted and fixed in a special scaffold with connecting irons welded to the column base and set in the formwork for the foundation base.

When filling the columns, the concrete shear joints at the column heads were produced at the same time.

The precast elements of the slab were placed on only two auxiliary yokes at the beam ends. A third yoke support in the center of the field would have required auxiliary foundations.

3.2 Tunnel

In the tunnel, only three concreting cycles were required, namely

  •  invert
  •  walls
  •  In-situ concrete for the slab

were required.

All horizontal construction joints between floor slab and tunnel outer walls were secured with joint plates 300 x 2 mm.

Due to the continuous floor slab, 3 auxiliary yokes per precast element could be used for placing the precast floor elements in the tunnel section.

Formwork and auxiliary scaffolds for the construction of a tunnel section were also kept in stock in triplicate in order to maintain a weekly cycle.

4. Literature

[1] Kreativ planen - Ideenwettbewerbe bei der Straßenplanung „Projekt B 30 Umgehung Ravensburg" Schriftenreihe der Straßenbau-Verwaltung Baden-Württemberg Heft 5

[2] B 30 Ulm-Friedrichshafen Ortsumgehung Ravensburg. Festschrift zur Verkehrsfreigabe

[3] Hilsdorf, Hubert K.: Betontechnologische und ausführungstechnische Maßnahmen bei der Erstellung des Tunnels und der Galerie im Zuge der B 30 - Umgehung Ravensburg. Zwischenbericht (unveröffentlicht) der Universität Karlsruhe

[4] Bernhardt, Klaus: Arbeitstagung Brücken- und Ingenieurbau Dresden (11. -13.06.1996). Besonders gestaltete Bauwerke im Zuge der Umgehung Ravensburg (unveröffentlich)


  • Region: Ravensburg, Baden-Würtemberg
  • Tunnel use: Road
  • Client: Land Baden-Würtemberg repr. by Regierungspräsidium Tübingen
  • Consultants: Leonhardt, Andrä u. Partner
  • Contractors: Arge: Georg Reischl GmbH & Co. KG, A. Hangleiter GmbH & Co. KB
  • Total length: 231 m (Tunnel BW21), 599 m (Galerie Nord), 76 m (Galerie Süd)
  • Clear width: 2 x 11,50 m (BW21), 11,50 m (BW20a/b)
  • Contract value: 13,7 Mio. DM (Tunnel BW 21), 17,6 (BW 20a/b)
  • Construction time: 12/1992 bis 02/1995 (27 Monate)