2018
Solihull, Birmingham
Worcestershire County Council
Alun Griffiths
CH2M Hill
Retaining Wall Failure and Reconstruction at Frankley Green Lane, Birmingham
MacWall® Vertica block facing MSE wall
Side view of the MacWall® Vertica blocks
Culvert headwall below MacWall® Vertica structure
MacWall® Vertica MSE wall – side view
Challenge
In December 2016, a concrete retaining wall supporting a roadway over the Brookhouse Farm culvert at Frankley Green Lane, approximately 10 km southwest of Birmingham, suffered catastrophic failure. The site, located in a low-lying area, was highly susceptible to surface water runoff and flooding.
Prolonged exposure to surface water led to severe erosion of the soil behind and beneath the retaining wall. As the foundation material was progressively washed away, the structural stability of the wall deteriorated, ultimately resulting in its collapse. The failure also caused part of the carriageway above to give way, creating a significant safety hazard and requiring urgent remediation.
Worcestershire County Council appointed CH2M Hill as consulting engineers to assess the damage and develop a long-term solution. Their Approval in Principle (AIP) specified the need for a concrete-faced mechanically stabilised earth (MSE) retaining wall designed to achieve a 120-year service life, ensuring durability and resilience in a challenging drainage environment.
Solution
Maccaferri, working with contractor Alun Griffiths, delivered an engineered retaining wall solution that met the stringent requirements of the AIP. The selected system was MacWall® 4.0, a high-performance segmental block retaining wall designed for soil reinforcement applications.
The solution utilised Paragrid geogrid as soil reinforcement, installed behind the MacWall® 4.0 block facing to create a mechanically stabilised earth structure. This combination provided excellent load distribution and long-term structural integrity. Both the Paragrid geogrid and MacWall segmental blocks are BBA-certified and compliant with the required 120-year design life, ensuring reliability and performance.
A key benefit of the MacWall® 4.0 system is its mortarless construction, allowing for rapid installation and reduced construction time. The system relies on a frictional connection between the geogrid layers and the segmental blocks, with reinforcement placed at regular intervals within compacted granular backfill to form a stable reinforced soil mass.
To prevent recurrence of the original failure, a comprehensive drainage solution was integrated into the design. A MacDrain geocomposite drainage layer was installed behind the retaining wall to efficiently manage groundwater and reduce hydrostatic pressure. This system was connected to a heel drain, discharging into the existing culvert to ensure effective water management and long-term stability.
Used Products
