The Immingham Underpass project was a critical infrastructure improvement designed to enhance highway access to the Port of Immingham, one of the United Kingdom’s busiest freight hubs.

To minimize disruption to rail operations, Freyssinet’s Autofonçage® bridge sliding method was used to install a massive reinforced concrete underpass beneath an active railway during a tightly scheduled holiday closure. The innovative approach allowed most construction activities to be completed before the track shutdown, significantly reducing risk, minimizing railway downtime, and ensuring the project was completed on schedule despite challenging winter weather.

  • Owner
    Highways England
  • Client
    Costain
  • Project Completion Date
    2015
  • Engineer
    Jacobs

Key Figures

Improving access to the Port of Immingham required the construction of new roadway connections to the existing transportation network in eastern England. As part of the project, a new two-lane highway underpass was needed beneath the freight railway line serving the port, one of the UK’s most heavily trafficked rail freight corridors.

Given the importance of maintaining rail operations, the project team selected Freyssinet’s Autofonçage® bridge sliding technology to install the structure efficiently during a limited rail closure window.

To ensure a smooth operation, the complete sliding system underwent full testing 48 hours before the scheduled bridge movement.

  • 4,130
    Bridge Weight (US tons)
  • 135 feet
    Slide Distance
  • 11
    Sliding Speed (feet per hour)

Minimizing Rail Disruption

Immingham bridge UK underpass

Because the railway serves a vital freight route supporting port operations, service interruptions had to be kept to an absolute minimum.

A 76-hour rail closure was scheduled during the Christmas holiday period to reduce impacts on rail traffic. Planning for the operation began several years before construction, allowing the project team to evaluate installation methods and develop comprehensive contingency plans.

During the design phase, Jacobs identified Freyssinet’s Autofonçage® technique as an ideal solution because it significantly reduced the amount of work required during the track closure.

How the Autofonçage® Method Works

The Autofonçage® system allows a bridge structure to be constructed adjacent to its final location rather than directly beneath the railway.

The reinforced concrete box structure is built offline while rail operations continue normally. Once construction is complete, the bridge is advanced into position using hydraulic strand jacks and a specially engineered sliding system.

The bridge moves across a lubricated layer of bentonite, which reduces friction and allows the massive structure to be pushed forward in a controlled manner.

During the installation process:

  • Hydraulic strand jacks push the structure forward from the rear.
  • Steel cables embedded within the bridge foundation guide the movement.
  • Passive anchors secure the system during installation.
  • Excavation and final grading can continue ahead of the advancing structure, maximizing construction efficiency.

This method dramatically reduces the work that must be completed during the track closure period.

Immingham bridge UK underpass

Advantages Over Traditional Installation Methods

Immingham Bridge Project: Underpass Installation Using Autofonçage®

Autofonçage® offers several advantages compared to conventional bridge installation techniques such as staged excavation, piling operations, and large crane lifts.

Key benefits include:

  • Most construction is completed before railway closure.
  • Temporary works remain outside the active railway embankment.
  • Reduced dependence on large cranes and heavy lifting equipment.
  • Lower sensitivity to adverse weather conditions.
  • Improved safety and schedule reliability.
  • Reduced impact on rail operations.

Perhaps most importantly, the method allows rail traffic to remain operational during nearly all phases of construction.

Overcoming Challenging Conditions

The value of the project’s extensive planning became evident when installation coincided with one of the harshest winter seasons experienced in the United Kingdom in several years.

Heavy rainfall created concerns regarding embankment stability leading up to the bridge slide. Thanks to advance preparation and contingency planning, the project team had the necessary equipment and procedures in place to respond quickly.

When sections of the embankment became unstable, crews were able to safely remove loose material and reshape the slope to restore stability without affecting the overall project schedule.

Immingham bridge UK underpass

Successful Installation

Immingham Bridge Project: Underpass Installation Using Autofonçage®

The Immingham project represented only the second use of the Autofonçage® bridge sliding method in the United Kingdom, although Freyssinet had successfully employed the technology across Europe for more than twenty years.

Work began on Christmas Eve immediately after the railway line was closed. Crews removed the rails and completed excavation activities before initiating the bridge slide at approximately 9:00 PM on Christmas Day.

Despite challenging weather conditions, the 4,130-ton structure was moved into its final position in less than 12 hours. The railway infrastructure was subsequently reinstated, and the track closure was lifted within the planned 76-hour window.

The successful installation demonstrated the effectiveness of the Autofonçage® method for delivering complex underpass projects while minimizing impacts on critical transportation networks.

Risk reduction and contingency planning meetings started in the design phase, two years before the box slide. Initially, Freyssinet contributed to Jacobs’ risk register, which was subsequently adopted and developed by Costain. We became an important part of the integrated project team, attending specific risk meetings with Costain and their other subcontractors.

Our contribution was highly valued, especially by the earthwork’s contractor. Costain invested time developing ‘what if’ scenarios with the supply chain and, collectively, contingency measures were identified.

Kevin Bennett  
Project manager, Freyssinet UK

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