Delivering underground infrastructure in today’s environment requires more than structural compliance. Projects are increasingly constrained by programme pressures, site access limitations, safety requirements, and carbon reduction targets. For designers and project managers, this creates a need to reduce installation complexity while maintaining long-term structural performance.
Precast concrete systems
Traditional chamber construction methods, particularly precast concrete systems, often introduce challenges at installation stage. These include high unit weights, reliance on heavy lifting plant, extended installation times, and the requirement for concrete surround to achieve structural stability. While effective, these approaches can increase programme duration, cost, and environmental impact.
A key engineering challenge lies in managing combined vertical and lateral loads. As installation depth increases, so too does lateral earth pressure, which can govern structural performance. In many conventional modular systems, sidewall stiffness is insufficient on its own, requiring concrete backfill to prevent deformation under load.
Structural composite chambers offer an alternative approach by addressing stiffness and strength within the chamber design itself. By engineering higher sidewall rigidity and improved load distribution, it becomes possible to eliminate the need for concrete surround and simplify installation without compromising long-term performance.
One such development is the COMMAX structural chamber system, which has been engineered as a high-strength composite solution capable of supporting vertical loads up to 900 kN, compared to approximately 400kN for typical precast alternatives.
Independent testing under simulated in-situ conditions has also demonstrated strong lateral load resistance, with minimal sidewall deflection under pressure. This performance enables installation using compacted granular material alone, removing the need for concrete backfill and significantly reducing both installation time and material use.
Beyond structural performance, the system introduces measurable efficiencies on site when compared with precast concrete chambers:
- Installation time reduced from approximately five hours to one hour;
- Transport capacity increased from approximately three units to up to 70 flat-pack units per load;
- Unit weight reduced from approximately 7300kg to 307kg;
- Carbon footprint reduced by approximately 60%;
Figures are based on 1500 (L) x 1500 (W) x 1500mm (H) chamber size
These improvements are enabled through the use of thermoset glass-fibre reinforced composite materials, which provide a high strength-to-weight ratio and resistance to corrosion, while also enabling manual handling and reducing reliance on plant equipment.
Reducing complexity on site – integrated access systems
The chamber is configured as a modular system, using lightweight ring sections that can be supplied flat-packed or pre-assembled. This supports faster installation, improved logistics, and greater flexibility in configuration, while maintaining consistent structural performance.
Developed by the same engineering expertise behind globally recognised access cover systems, EJ, this approach also enables full integration between chamber and cover. By designing both components as a single system, compatibility is assured in terms of load transfer, fit, and performance, reducing interface risk on site and simplifying specification.
In this context, the development of COMMAX represents a broader shift in approach – from specifying individual components to delivering complete, integrated access systems that reduce complexity, improve installation efficiency, and maintain structural integrity from surface to service.
For decades, EJ has been trusted for high-performance access covers supporting critical infrastructure across transport and utility networks. However, the performance of an access system is not defined at surface level alone. Increasingly, whole-life performance depends on the structural behaviour of the chamber below ground.
COMMAX has been developed to address this gap – extending EJ’s expertise into subsurface infrastructure with a structural composite chamber designed to perform as part of a complete access system. The reduction in concrete usage, combined with lower transport volumes and simplified installation, contributes to a significant reduction in embodied carbon. This aligns with increasing industry focus on sustainable infrastructure delivery and whole-life carbon assessment.
From component supply to engineered systems
COMMAX represents a shift from component supply to engineered systems. By addressing both vertical and lateral structural performance – and removing traditional installation constraints – it provides a robust alternative to precast concrete chambers.
More importantly, it enables engineers to consider the access structure as a complete system, delivering improved performance, reduced risk, and greater efficiency from surface to service.
Contact EJ's business development team on 057 912 3100 for further information.