Decoding Your Geotextile Data Sheet: A Guide to Key Properties for Engineers

The Geotextile Technical Data Sheet (TDS) is your primary tool for selecting the right product. However, a list of numbers is useless without context. This guide translates engineering jargon into practical knowledge, empowering you to make data-driven decisions for separation, filtration, and reinforcement.

1. Physical Properties: The Basics.

• Mass Per Unit Area (Weight): Expressed in g/m² or oz/yd². Heavier fabrics (heavy duty geotextile fabric) typically indicate greater thickness and robust mechanical properties, but always verify performance numbers directly.

• Thickness: Measured under a specific pressure. Influences cushioning and planar flow capacity.

2. Mechanical Properties: Survivability & Strength.

• Grab Tensile Strength & Elongation (ASTM D4632): Indicates the force required to rupture the fabric. High strength is critical for reinforcement applications. Elongation at break shows ductility; woven fabrics have lower elongation than non-wovens.

• CBR Puncture Resistance (ASTM D6241): Perhaps the most critical index for survivability. Simulates the fabric resisting penetration by sharp aggregate or subgrade irregularities. A high value is non-negotiable for road or parking lot construction over rocky soil.

• Trapezoid Tear Strength (ASTM D4533): Measures resistance to tear propagation once initiated.

3. Hydraulic Properties: The Flow Factors.

• Apparent Opening Size (AOS) (ASTM D4751): Expressed as O95 (e.g., 0.15mm). This is the approximate largest particle that can effectively pass through the fabric. For filtration, you must select an AOS small enough to retain the base soil fraction but large enough to allow water passage. Incorrect AOS selection is a leading cause of system clogging or soil piping.

• Permittivity & Permeability (ASTM D4491): Measures the fabric’s ability to allow water flow normal to its plane (permittivity, Ψ) or within its plane (permeability, k). The fabric must be more permeable than the soil it protects.

Making the Match: For a French drain in sandy soil, prioritize filtration: select a non-woven geotextile with an AOS slightly smaller than the sand’s D85 and high permittivity. For a road over soft clay, prioritize separation and survivability: choose a fabric with very high CBR puncture and tensile strength.

At HZ Geotextile, our TDS are transparent and comprehensive. Our technical team can help you interpret these properties for your specific soil stabilization or drainage challenge. Contact us via www.hzgeotextile.com for a consultation.