1. General

1.1 Task

The A 66 federal freeway links the regional center of Fulda on the A 7 freeway with the Rhine-Main region. In the course of the further construction of the A 66, an approx. 7 km long gap was closed in the Neuhof area. In this section, the new A 66 closely follows the Frankfurt-Göttingen rail line. Parallel to the road construction measure, DB AG planned a line improvement with an expansion speed of 160 km/h in this section of the line and the reconstruction of Neuhof station. Once the planning approval decision had been issued, work on the joint road and rail construction and upgrading project could begin in the fall of 2005. Due to the close interlinking of the various construction activities on the highway, tracks, waterways and supply and disposal facilities, the overall construction measure was awarded as a joint project. The overall project comprised

• the construction of various civil engineering structures and the construction of the new line with all ancillary works on behalf of the Federal Republic of Germany
• the upgrading of the Frankfurt-Fulda railroad line and the reconstruction of Neuhof station on behalf of DB Netz AG
• the construction of a P+R facility on behalf of the municipality of Neuhof.

The 3.5 km long section between Neuhof-Süd and Neuhof-Nord represents the technically most demanding part of the gap closure of the A 66. The centerpiece is the 1.6 km long Neuhof Tunnel. The construction of the tunnel has significantly reduced noise and exhaust pollution in the Neuhof area. However, the construction of the new tunnel necessitated numerous follow-up measures to the existing infrastructure. The entire supply and disposal network of the municipality and other utility companies had to be redesigned, the course of the Fliede River had to be altered, and the main local connection bridge over rail, road and water had to be demolished and rebuilt. The realization of the overall construction measure contributes significantly to the enhancement of the quality of life in the region. In addition to reducing noise and pollutant emissions, a pedestrian underpass and a P+R facility were added to the station area. For the entire region of Eastern Hesse, the completed A 66 in the district of Fulda represents a significantly improved connection to the Rhine-Main area with all the advantages of a good traffic infrastructure.

1.2 Structural design

The architectural design of the portals took into account the topographical features at the construction site. Both portals were opened gallery-like on the right-hand side over a length of 40 m in the direction of entry. The ceiling of the tunnel frame rises continuously from 4.80 m to 5.80 m in the last four blocks. This creates a trumpet-like widening of the tunnel portals. These measures succeed in integrating the surrounding landscape and improving the incidence of light.

2. Building design

2.1 General

For economic and hydrological reasons, the 1610 m long tunnel runs close to the surface. Therefore, it could be constructed in cut-and-cover method. The tunnel structure is divided into several sections. In the southern section, the tunnel runs on an embankment and is actually an enclosure structure that was subsequently covered. In this section, the laid Fliede River passes under the tunnel in free flow. In the middle section, the tunnel plunges into the terrain and the groundwater at a longitudinal gradient of approx. 1.86%. At the low point, the upper edge of the tunnel runs just below the existing ground level. After that, the gradient in the tunnel rises again with an inclination of 1.65%. In this section, a new platform and the exits to the pedestrian underpass were partially built directly on the tunnel outer wall. In the northern section, the tunnel crosses the Opperz ridge with an overburden of up to 13m. Here, the tunnel emerges again from the groundwater 122 New Tunnel Neuhof (A 66) l. i and runs above the groundwater level to the north portal. The uphill excavation slope with an inclination of 70° was secured with a back-anchored shotcrete lining.

2.2 Construction

The tunnel has a standard cross-section of 26t according to the "Guidelines for the Equipment and Operation of Road Tunnels (RABT)". The cross-section consists of a carriageway width of 7.50 m in each direction and 1.0 m wide emergency walkways on both sides. The structure was designed as a two-row frame. It consists of a water-impermeable concrete structure of strength class C 30/37 in accordance with the "Additional Technical Terms of Contract and Guidelines for Engineering Structures (ZTV-ING)", Part 5, Section 2. In the first section, the frame is open and founded shallowly on strip footings and soil replacement above the groundwater level. In the other sections, the structure was designed with a closed frame base and also founded flat. The tunnel's frame structure consists of 90 cm thick walls and a 1.0 - 1.20 m thick slab. In the area of the closed frame section, the bottom thickness is 1.0 m. The tunnel blocks are separated at intervals of 10 m by space joints with internal elastomer joint strips.

Behind the gallery-like open tunnel portals, 30 m long ventilation partitions adjoin the central partitions of the north and south portals in the area of the tunnel aprons.

2.3 Tunnel equipment

The Neuhof tunnel was equipped with the latest operating and safety technology in accordance with the RABT.

Lighting

The tunnel's lighting is arranged in a single row off-center above the main lane so that only one lane has to be closed in the event of lighting maintenance.

Tunnel ventilation

An automatic longitudinal ventilation system is installed in both tubes. Sensors measuring turbidity, CO and flow velocity automatically activate the fans for fresh air ventilation. Ventilation and smoke extraction in case of fire are ensured by 16 reversible jet fans per tunnel tube. At the portals, ventilation partitions prevent air escaping from the exit portal from being partially sucked back into the entrance portal and smoke from being carried into the second tube in the event of a fire.

Traffic installations in the tunnel apron

In the tunnel apron and at both portals, traffic lights and blocking devices are provided to be able to close the tunnel at short notice in hazardous situations.

Safety facilities

Escape and rescue routes

There are two emergency stopping bays in each tube, which are located approximately at the third points of the total length. In the areas of the emergency stopping bays, there are crossings with gates in the tunnel center wall. Five escape doors in the tunnel center wall provide a means of rescue into the second tube. Five further escape routes lead to the outside via ramps and a stairwell. The escape stairwell is equipped with an overpressure ventilation system that is activated automatically. On the side of each tunnel tube facing the cross passages, combined escape route marking and orientation luminaires have been arranged at intervals of ä 25 m. In the center between these luminaires, escape route marking and orientation luminaires have been installed. In addition, self-illuminating marking elements on the emergency walkways mark the escape routes centrally between these guidance devices. Indicator lights to identify the escape and rescue routes and emergency exits in the event of fire are located throughout the tunnel, at the emergency exits and in the operations building. To improve visual guidance, the escape doors and crossings between the west and east tubes and the emergency exits to the outside are also marked with LED strip lighting.

Emergency call stations

Emergency call stations with fire alarm equipment and hand-held fire extinguishers are located at intervals of < 150 m on the outer tunnel wall.

Communication equipment

The operational equipment also includes public address systems, tunnel radio and video surveillance. The tunnel radio is designed exclusively for digital radio. Reception of at least one radio station with traffic radio identification (RDS) is guaranteed in the tunnel. The system allows the tunnel control center to speak into the radio frequency. The video images of the uninterrupted visual monitoring of the tunnel tubes, escape routes and emergency exits, as well as the emergency access road and the operations building, are transmitted to the Hesse tunnel control center in Eschwege.

Central systems

An operations building was erected for the Neuhof tunnel, which houses the supply technology for the entire structure. At the tunnel low point, the retention basin and the storage of the extinguishing water supply are also located under the operations building.

Control system

Tunnel operation is fully automatic with remote monitoring and operation by the tunnel control center in Eschwege. From there, all system components required for control and visualization are monitored.

3. Construction work

The groundbreaking ceremony for the Neuhof construction section was held on October 6, 2005, at the same time as the construction measures of Deutsche Bahn AG. Due to the spatial and temporal dependencies, the numerous partial construction measures could only be successfully realized together in a large construction contract spanning rail, road and municipal facilities. The joint handling of the overall construction measures presented a particular challenge. The various problems resulting, for example, from the different technical regulations of the authorities responsible for the construction were solved in numerous detailed consultations. The core area was put out to tender throughout Europe as a large construction contract with four subsections and awarded to a consortium of three construction companies. The road construction authority was responsible for the contractual management of the overall project on the client's side. Separate subsections were also handled independently by the respective client. Construction work on the tunnel began in March 2008. During the construction of the tunnel, the middle tunnel section with a length of approx. 800 m proved to be the most difficult. It could only be constructed after the old tracks had been removed and the new tracks completed. For dewatering, impermeable shoring with transverse bulkheads at intervals of approx. 80 m was necessary. The shoring was constructed in some areas as a tied-back, overcut bored pile wall and in the remaining areas as a tied-back sheet pile wall with vertical sealing. After completion of the structure, the sheet piles were pulled out again. Horizontal excavation sealing was achieved by means of a 590 m long, 1.0 m thick unreinforced underwater concrete base. The invert was constructed using the contractor method and secured against uplift with grouted anchors. Above the invert, a 45 cm thick filter layer was installed to allow groundwater to flow around the tunnel after completion. The very complex underwater work was carried out to avoid lowering the groundwater level.

The construction sequence of the overall measure had to be aligned with train and closure breaks on the highly frequented railroad line. During the entire construction phase, existing road and rail traffic had to be routed through the construction areas of the new road and new tracks. In addition, there were the inner-city pedestrian traffic and the station users who had to cross the construction site almost during the entire construction period. The construction measure, which lasted several years and involved numerous interdependencies during ongoing operations and in the area of the narrow development, was successfully completed on the basis of years of engineering planning and coordination. On September 13, 2014, the Neuhof Tunnel was opened to traffic.

4. Literature

[1] Wagner, M.: Der Lückenschluss der A 66 im Landkreis Fulda.VSVI-Journal2014

[2] Wagner, M.: Der Bau der Bundesautobahn A 66 im Bereich Neuhof.VSVI-Vortragsveranstaltung 2013

[3] Konheiser, K.: Der Bau der A 66 im Kernbereich Neuhof. VSVI-Journal 1/2010

[4] Amt für Straßen- und Verkehrswesen Fulda: Der Bau der A 66 im Bereich Neuhof - „Operation am offenen Herzen". Informationsbroschüre Stand 10/2009

[5] Bruckner, K.; Hansel, U.; Pelke, E.; Sachs, F.: Chancen der Zusammenarbeit Straße - Schiene aus Sicht der Hessisehen Straßen- und Verkehrsverwaltung. Eisenbahn Ingenieur Kalender 2009 

 

 

• Country: Germany
• Region: Hesse
• Tunnel utilization: Traffic
• Type of utilization: Road Tunnel
• Client: Federal Republic of Germany, Land of Hesse
• Consulting Engineer: Amt für Straßen- und Verkehrswesen Fulda
• Contractor: JV BAB A66 Neuhof: Hermann Kirchner Hoch- und Ingenieurbau GmbH/Hochtief Construction AG/Bickhardt Bau AG
• Main construction method: Open
• No. of tubes: 1
• Tunnel total length: 1,610 m
• Cross-section: standard RQ 26t
• Contract Volume: 53 mill. Euro (roughwork)
• Construction start/end: 3/2008 till 9/2014