What is the purpose of the trapezoidal tear test?

To determine the force required to propagate a tear from a pre-cut slit in a geotextile specimen (Clause 3).

What is the specified speed for the tensile testing machine?

The constant rate of extension (CRE) is 300 ± 10 mm/min (Clause 7.3).

How many specimens are tested?

A minimum of five specimens in the machine direction and five in the cross-machine direction are required (Clause 6.1).

What are the dimensions of the test specimen?

The specimen should be a rectangle of 100 mm width and 200 mm length (Clause 6.2).

IS 13325 Part 4

: 2020

Geosynthetics - Geotextiles - Methods of Test for Mechanical Properties

CurrentSpecializedTesting MethodGeotechnical · Geosynthetics and Ground Improvement

Archive.org BIS Portal Google

This standard (Part 4) specifies a method for determining the trapezoidal tear strength of geotextiles. It outlines the test principle, apparatus, specimen preparation, procedure, and calculation for measuring the force required to propagate a tear in the material.

Specifies methods for determining mechanical properties of geotextiles such as tensile strength, puncture resistance, and tear strength.

Quick Reference Values

Test specimen dimensions100 mm x 200 mm

Initial slit length15 mm

Rate of jaw separation (CRE)300 ± 10 mm/min

Pre-tension for specimens ≤ 200 g/m²1 N

Pre-tension for specimens > 200 g/m²2 N

Number of specimens per directionMinimum 5

Key Formulas

Tear Strength (N) = Average of the five highest peak forces recorded during the test for each specimen.

Practical Notes

Ensure the specimen is clamped perfectly along the non-parallel sides of the trapezoid to ensure force is applied correctly.

The test result is an average of the five highest peaks from the force-elongation curve, not just the single maximum peak.

This test is critical for applications where the geotextile might be subjected to puncture and subsequent tearing, such as under sharp aggregate.