Weak, wet subgrades are among the most challenging conditions in construction. Equipment gets stuck, aggregate disappears into the mud, and schedules slip. Geotextiles for subgrade improvement offer a systematic, engineered approach to conquering soft ground.
Level 1: Separation (The Foundation)
The most basic intervention. A geotextile is placed directly on the prepared subgrade before aggregate placement. Its sole function: prevent subgrade soil from intruding into the aggregate layer. This preserves aggregate thickness, maintains drainage, and provides a stable working surface. Suitable for subgrades with moderate strength (CBR ≥ 3).
Level 2: Reinforcement (Enhanced Performance)
When subgrade strength is very low (CBR 1-3), separation alone is insufficient. A high-strength woven geotextile is specified to provide tensile reinforcement. The fabric tensions under load, distributing wheel loads over a wider area and reducing vertical stress on the subgrade. This allows:
Thinner aggregate sections (cost savings).
Higher trafficability for construction equipment.
Reduced rutting during construction and service.
Level 3: Geotextile-Reinforced Working Platforms (The Heavy Lift)
For extremely soft subgrades (CBR < 1) or very high loads (deep foundations, heavy cranes), a geotextile-reinforced working platform is a designed geotechnical structure. This involves:
Site investigation: Accurate measurement of undrained shear strength.
Design methods: Based on limit equilibrium or bearing capacity theories (e.g., British Standard BS8006, Giroud & Han method).
High-strength geotextile selection: Typically woven polyester or polypropylene with tensile strength > 100 kN/m.
Controlled construction: Aggregate placement from the "edge" inward to mobilize reinforcement.
Construction Best Practices on Soft Ground:
Minimize Subgrade Disturbance: Do not overwork or pump the subgrade during preparation.
Proper Overlap: Ensure adequate overlap or seaming to maintain continuity.
Aggregate Quality: Use angular, well-graded aggregate; do not drop from height.
Thin Lift Placement: Place the first lift in thin layers (150-200mm) with light equipment.
The Outcome:
A stable, safe working platform that enables construction in conditions previously considered unworkable. This isn't just about solving a site problem; it's about unlocking project potential.
HZ Geotextile supplies a full range of subgrade improvement fabrics, from standard separation grades to ultra-high-strength reinforcement wovens. For design assistance or product recommendations, visit www.hzgeotextile.com.
