Theoretical data sheets meet their ultimate test in the field. For one of Europe’s busiest coastal logistics terminals, a critical internal access road servicing container storage yards was in a state of perpetual distress. Built on deep, soft marine clays, the road exhibited severe rutting, pumping, and required monthly regrading, disrupting operations and incurring exorbitant maintenance costs. Standard solutions had failed. This case study details how a collaborative engineering approach and a custom composite geotextile solution resolved a chronic problem, transforming cost center into reliable infrastructure.
Background: The Problematic Site
Location: Northern European Coastal Terminal
Soil Conditions: 4-6 meters of very soft, saturated silty clay (undrained shear strength, Su < 25 kPa) underlain by dense sand.
The Challenge: The road needed to support daily traffic of heavy container handlers (wheel loads exceeding 50 tons). Traditional methods—thick aggregate bases, standard woven geotextiles—only provided temporary relief. The underlying clay would laterally squeeze and penetrate the base, leading to rapid failure.
Phase 1: Forensic Analysis & Limitations of Standard Solutions
A geotechnical review confirmed the issue: the soil’s extremely low bearing capacity and high water content caused classic subgrade failure. Standard separation geotextiles were being punctured. High-strength reinforcement geotextiles alone could not address the pore water pressure buildup that weakened the clay. A simple drainage geotextile lacked the strength. The solution needed to combine three functions simultaneously: Separation, Reinforcement, and Drainage.
Phase 2: Co-Development of a Custom Composite Geotextile
The terminal’s engineering team partnered with our R&D department to develop a purpose-built solution. The goal was to create an integrated system that would:
Prevent aggregate contamination (Separation).
Provide a tensile membrane to distribute loads (Reinforcement).
Facilitate rapid vertical and lateral drainage of pore water from the clay layer to accelerate consolidation and gain strength (Drainage).
The resulting product was a sandwich-style composite geotextile:
Core: A thick, high-permittivity needle-punched non-woven geotextile (300 g/m²) for in-plane drainage (transmissivity).
Surfaces: Bonded on both sides were layers of a high-modulus woven polypropylene geotextile (120 kN/m tensile strength). This provided the necessary puncture resistance and tensile membrane effect.
This composite structure was manufactured in 5.2-meter widths to minimize seams and was designed for specific roll weights to ensure easy handling with on-site machinery.
Phase 3: Installation & Performance Monitoring
Installation followed a strict protocol:
Proof Rolling: The weak subgrade was lightly proof-rolled to identify the worst areas.
Composite Placement: The custom composite geotextile was deployed directly onto the prepared clay.
Aggregate Placement & Compaction: A 400mm granular base was placed and compacted in lifts.
Monitoring: Survey pins and piezometers (to measure pore water pressure) were installed.
Results & Verified Performance
The results were monitored over 12 months:
Immediate: Construction traffic showed no rutting during build-out.
3 Months: Piezometer data showed a 60% reduction in excess pore water pressure compared to adjacent untreated areas, indicating effective drainage and consolidation.
12 Months: The road surface showed less than 10mm of deformation under continuous heavy traffic, compared to over 150mm previously. Maintenance grading was eliminated.
Key Success Factors & Lessons Learned:
Collaboration is Key: The solution emerged from open dialogue between the client’s geotechnical engineers and the manufacturer’s product specialists.
Function-Driven Design: Focusing on the required functions (S-R-D) rather than off-the-shelf products led to innovation.
Lifecycle Cost View: The higher initial cost of the custom composite was offset within 18 months by eliminating maintenance, proving the return on investment.
Conclusion: Beyond Products to Engineered Outcomes
This case study exemplifies modern geotechnical problem-solving. It demonstrates that when challenging site conditions defy standard prescriptions, the answer lies in partnership with a manufacturer capable of custom engineering. The success was not just in a new fabric, but in a systematic approach: understand, design, validate.
At HZGeotextile, we pride ourselves on being a solutions engine, not just a mill. Our technical team is equipped to engage in this level of collaborative problem-solving. Browse our portfolio of documented case studies and learn how we can co-develop the right solution for your unique ground challenges at www.hzgeotextile.com/case-studies.
