2024
Rochdale
Rochdale Borough Council
FW Sherratt Ltd
N/A
Retaining Wall Reconstruction at River Roch Using Terramesh System
Challenge
A masonry retaining wall approximately 30 metres long, supporting a car park above the River Roch, failed as a result of scour at its foundation. The erosion weakened the structure to the point of collapse, requiring urgent replacement. Rochdale Borough Council appointed Civil Engineering & Building Contractors FW Sherratt to carry out the reconstruction of the wall. The proposed new structure was to be around 5 metres high, with its final length to be determined during construction, as the works needed to continue until a stable section of the original wall was reached.
The initial construction approach involved installing galvanised sheet piles to enable the formation of a reinforced concrete base and wall. However, due to the riverside location and associated groundwater conditions, the contractor was unable to achieve sufficiently dry formation levels to proceed with concrete pours. These conditions made the original design difficult to implement, leading the contractor to consider alternative retaining solutions that could be installed more effectively in a wet environment.
Solution
Maccaferri proposed the use of its Gabion Terramesh system as an alternative to the reinforced concrete wall. This system consists of modular units that form a rock-faced reinforced soil structure, offering a durable solution with a design life of 120 years and supported by BBA certification.
Unlike traditional gabions, Terramesh units incorporate an integral steel wire mesh tail that extends from the front face of the unit back into the retained soil, providing reinforcement. In this case, the tail extended approximately 4 metres into the slope. Given the overall height of the wall and the favourable ground conditions, no additional geogrid reinforcement was required.
The completed wall stands at approximately 5 metres in height, extending from Molesworth Street Bridge to around 50 metres downstream. Compared to a conventional mass-gravity gabion wall of similar height, the Terramesh system required significantly less stone fill, reducing both material use and associated costs. Its permeability and flexibility also made it well suited to the site conditions, allowing construction to proceed despite the presence of water, which had previously prevented the use of concrete.
