High-performance structural drainage and vibration damping for HS2 Carol Green Underbridge
- Location
- HS2 Carol Green Compound, Coventry, CV7 7BW
The background
Geosynthetics Limited worked alongside Balfour Beatty VINCI (BBV) to deliver a critical infrastructure solution for the HS2 Carol Green Underbridge in Coventry. This high-capacity rail node represents a complex engineering environment where the new HS2 lines pass directly above the existing West Coast Mainline.
The project required a multi-functional approach to ensure long-term structural integrity while managing the intense dynamic loads unique to this dual-corridor intersection.
Our client’s requirements
The engineering specifications for the underbridge were exceptionally rigorous. Our client needed a solution capable of performing three vital functions simultaneously:
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Hydrostatic relief: Managing high water pressure against the bridge abutments.
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Membrane protection: Shielding the delicate, liquid-applied waterproofing membranes from mechanical damage during aggressive backfilling and compaction.
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Vibration mitigation: Absorbing the “ground vibration boom” and complex fatigue caused by high-speed trains passing both inside and above the structure.
- Drainage: Provide a free-flowing pathway to prevent hydrostatic pressure build-up against the structure.
- Waterproofing Protection: Prevent the liquid-applied waterproofing from being damaged throughout backfilling, compaction and beyond.
- Traditional methods, such as porous blocks or granular stone, were deemed insufficient. These options were not only carbon-intensive to transport but also lacked the flexibility required to provide a decoupling layer against structure-borne vibration.
Our value engineered solution
Geosynthetics Limited specified Enkadrain™ ST, a high-performance geocomposite that integrates drainage, protection, and vibration damping into a single vertical layer.
Designed with a high-strength 3D polyamide core, Enkadrain™ ST maintains a stable drainage void even under the extreme surcharge loads generated by HS2 rail traffic. By installing the system vertically against the external tunnel walls, we created a continuous drainage path from roof level down to the formation drainage.
Key benefits delivered:
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Integrated shock absorption: Unlike rigid stone drainage, the 3D monofilament structure acts as a decoupling layer. It absorbs and dissipates vibrations, reducing noise and long-term fatigue on the concrete without the need for expensive, complex spring systems.
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Structural protection: The geocomposite acts as a robust, sacrificial shield that prevents punctures to the waterproofing system during construction and throughout the asset’s lifecycle.
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Logistical and carbon efficiency: One full load of Enkadrain™ ST provides the same flow capacity as over 1,200 wagon loads of traditional drainage stone. This massive reduction in vehicle movements directly supported HS2’s commitment to a lower carbon footprint.
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Commercial savings: The project realised an approximate 50% saving in material costs compared to traditional aggregates, with additional gains found in reduced installation time and labour.
Download the case study to learn the results of this project and see how Enkadrain™ ST can protect your critical infrastructure.
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