RADIX Ground Screw Foundations for Temporary Modular Bridge

Overview

Temporary access solutions in a sensitive riverside environment

Located at Bedford Lock, this project involved the installation of foundations to support a temporary access bridge, maintaining vehicle access for essential maintenance and repair works at the lock. RADIX worked alongside Beaver Bridges, providing foundation support for a 32 m bridge designed to accommodate vehicle loads of up to 44 tonnes.

The site presented several technical and environmental constraints. Foundations were required to be installed in very close proximity to the riverbank, with careful consideration given to bank stability and load transfer. Ground conditions were characterised by high groundwater levels only a short distance below the surface, resulting in reduced soil stiffness and limited lateral capacity.

In addition, the site was bordered by mature trees and open public parkland. This required controlled plant movements, minimal material handling, and a reduced site footprint to limit disturbance while maintaining safe access for the public throughout the works.

Solution

Achieving lateral stability in saturated ground near the river edge

RADIX installed 13 extendable 89mm screw piles, each fitted with 1m extensions and additional helical sections, using an 8-ton tracked machine. The piles were designed to work in saturated ground conditions where lateral capacity, rather than vertical load, was the primary engineering challenge.

In soft, waterlogged soils, lateral resistance is achieved through increased helix area, embedment depth, and pile grouping. To counter the reduced lateral soil strength near the riverbank, RADIX incorporated extra helical sections and an additional pile into the layout, enabling the system to achieve the required installation torque, which directly correlates with pile capacity in both axial and lateral performance.

Despite restricted access caused by trees and proximity to the water, the compact installation footprint of screw piling allowed steady progress with controlled movements. The bridge was installed on custom steelwork supplied by Beaver Bridges, forming a temporary structure capable of supporting heavy vehicle movements to and from the lock.

The full foundation installation was completed in two days, after which the bridge was lifted into position. Once the project is complete, the screw piles can be removed cleanly, leaving no permanent trace of the structure.

Sustainability & Environmental Benefits

Protecting the riverbank, public space, and natural landscape

Working in a public space naturally drew interest from members of the public, many of whom stopped to ask questions about the installation. The RADIX team welcomed the opportunity to explain screw piling, and the concept was met with genuine enthusiasm, particularly around its low-impact footprint and environmental benefits.

This project demonstrates why screw piles are ideally suited to temporary works in sensitive riverside and public environments:

• No excavation of the riverbank, reducing the risk of erosion or collapse
• Minimal disturbance to saturated ground, avoiding dewatering or ground replacement
• Reduced vehicle movements, particularly important in an open public park setting
• Fully reversible foundations, allowing the site to be restored quickly once works are complete
• Lower environmental impact than driven piles or cast-in-place foundations, which would require extensive groundworks and longer programmes

By avoiding invasive foundation methods, RADIX helped maintain the integrity of the River Great Ouse’s banks while enabling critical infrastructure works to proceed safely and efficiently.