Performance tests are used to assess the performance of geosynthetics under site-specific situations and are devised to suit the application.
They can extend from laboratory tests to the monitoring of large-scale models, field trials and full-scale installations.
More detail on tests:
This standard specifies a method for determining the tensile creep and creep rupture behaviour of geotextiles and geotextile-related products in an unconfined situation.
Application of this standard is limited to those products and applications where the risk of collapse of a structure due to premature failure or to strain / time variation of the reinforcement under constant load is of critical importance.
As the test is carried out over a long period of time and the procedure is complex, it is recommended that the test not be considered a routine quality control test. The results of the test may not be representative of the performance of the products when subject to soil pressures.
A representative sample of geosynthetic is gripped between two clamps and a static or dead weight attached to the lower clamp exerting a force equivalent to a predetermined percentage of its ultimate break force. The strain is tracked over a period of time and the information used to assist in reinforcement design.
Long Term Gradient Ratio (LTGR)
This test method covers a performance test applicable for determining the soil-geotextile system permeability and clogging behaviour for cohesion-less soils under unidirectional flow conditions.
A soil sample is reconstituted over a geotextile filter in a clear cylindrical permeameter. Various head differentials are applied across the soil / geotextile system. Manometer ports at fixed positions along the profile of the system, allow for measurement of flow rates and differential heads. This information can be used to determine the Hydraulic Gradient across a soil / geotextile system.
A 100mm layer of low permeability soil or clay is reconstituted in a clear cylindrical permeameter. A differential head of water is applied across the soil specimen. The permeant is allowed to drain through the soil media and the resultant reduction in liquid level is recorded against time and the data used to determine system permeability.
This is an in-house test.
According to the specification, this test covers the material requirements for geotextiles. It is also used with site specific soil for performance assessment.
A sample of geotextile is clamped at the bottom of a steel panier using a stainless steel mesh. A selection of glass beads of various designations is placed on top of the geotextile. The panier is repeatedly dunked in a trough of water and drained for a minimum of 1000 cycles. The glass beads that pass through the geotextile are collected and the largest particle size recorded.
View the test in action below.