Castleton Rail Bridge Demolition

Demolition of a post-tensioned railway bridge deck over the M62. Existing abutments and the central pier were retained for the replacement bridge.

Client: Murphy Group

Demolition Contractor: P.P. O’Connor

Overview

The Castleton Bridge over the M62 was a double span post-tensioned concrete rail bridge that was replaced as part of a £20m infrastructure upgrade.

The project had significant constraints, due to the safety measures and exclusion zone required for demolishing a post-tensioned bridge with tendons that were either badly grouted or effectively not grouted at all. 

The bridge was demolished during a road possession with the existing abutments and central pier retained for use for the construction of the replacement bridge.

Andun Engineering Consultants provided the demolition engineering and associated temporary works for the removal of the original structure.

Constraints and Challenges

Post-Tensioned Design

The key engineering challenge was that the bridge was constructed using post-tensioned concrete spans. 

Upon inspection, during the specialist investigation report, the span tendons were effectively ungrouted, therefore increasing the risk of explosive release during demolition. 

This meant the demolition methodology had to be designed to take into account the risk of the bridge collapsing during the demolition when the tendons were compromised. 

This led to a very specific demolition method., including the use of shipping containers as props, specialist demolition plant, and a strict exclusion zone being put in place with no workers or machinery being permitted to go under the bridge or next to abutments once demolition began.

Due to this constraint, backup specialist demolition excavators and equipment were put in place as a contingency in case of a breakdown.

Retention of Abutments and Central Pier

The abutments and central pier were retained to be used for the replacement bridge, which meant that they had to be protected during the demolition of the bridge.

The protection proposed was simple and effective. It consisted of timber ekki mats that were strapped to the abutments using ratchet straps, which were anchored in with ring tie anchors. 

Road Possession 

The demolition had to occur during a limited road possession window to minimise disruption on the busy M62 motorway.

In addition to the 20ft containers under each span to support the bridge during the latter stages of demolition, ekki matts were also placed on the road surface and barriers to provide protection to the road infrastructure during the demolition process.

Demolition Methodology

The demolition was carried out using large mechanical excavators, working in a “typewriter fashion” from both sides of the bridge towards the centre.

This method ensured the bridge’s stability throughout the process, gradually reducing the structure until it could no longer support itself. When the bridge could no longer sustain its weight, it was allowed to collapse in a controlled manner onto the containers.

This prevented debris from impacting the motorway and allowed for safer, more manageable processing of the remaining materials.

After the controlled collapse, the remaining sections of the bridge were processed while the structure rested on the abutments, central pier, and containers. All materials were then cleared from the site, ensuring the motorway could be reopened on schedule.

Project Completion

The Castleton Bridge demolition on the M62 was a carefully coordinated operation involving detailed planning, expert execution, and strict safety measures. 

The project was described by New Civil Engineer as a potential template for future remediation of Network Rail’s “at risk” post-tensioned bridges.