Geotextile Testing Machines

This test is conducted to evaluate the resistance of geosynthetic / geotextile to damage during installation due to dropping of sharp edged or sharp pointed stones on a geosynthetic/ geotextile directly. In this test, a geosynthetic, geotextile is clamped to yield a clear diameter of 150 mm and a brass cone of 45 degree included angle, having a weight of 1 kg, is dropped through a height of 500 mm. The diameter of the resultant hole is measured with a graduated conical device. The smaller the hole, the greater the resistance of geosynthetic /geotextile to damage. When used in combination with other direct tensile test results, it provides a convenient means of qualitative comparison.

Permeability of a geotextile must be substantially greater than that of the protected soil, so that water can pass freely from the soil through the fabric without build up of hydrostatic pressure. A high value of the permeability of the geotextile also infers that partial clogging will not reduce the permeability. Both Constant and Falling Head permeameters are generally used for measuring normal permeability.

The test involves sieving rounded particle sizes for which 5% or less by weight pass through the geotextile. The Apparent Opening Size (AOS) is defined as 'Retained On' size of that fraction expressed as a standard sieve number (size). The test is widely used for relative comparison amongst the geotextiles. Thus AOS is a means of correlating geotextile pore structure to an equivalent screen mesh size. The apparatus consist of a 20 cm dia brass frame with clamp, a receiver and a lid.

Gradient ratio is the ratio of hydraulic gradient through the geotextile plus 25.4 mm of the soil to that of hydraulic gradient through the adjacent 50.8 mm of the soil. It is determined after 24 hours of flow.

Specifications

• Specimen diameter : 100 mm
• Mould for compaction of soil : 10 cm dia x 11.2 cm high
• Head of water : Upto 37.5 cm