Field Testing Geomembranes

Geomembrane Field Testing

Layfield performs many different types of tests to ensure that the geomembranes we install will meet your performance requirements.

Layfield performs frequent destructive and non-destructive tests on all of the geomembranes that we install. Our field crews are fully trained in the performance of all geomembrane field testing. Our documented Field QA manual is available with further details of Layfield testing standards.

Destructive Testing

In order to verify that the field seams prepared will meet the project strength requirements Layfield performs destructive testing. A calibrated portable tensiometer is taken to site and seam specimens are tested in peel and shear. Physical test results (adjusted to 23 deg C) are compared to project specifications. Seams that do not meet project specifications are repaired and retested. Destructive tests are performed on qualification welds and on weld samples. Further details on destructive testing can be found in ASTM D6392.

Qualification Welds

Qualification Welds are welds performed on small pieces of project material at site to verify welder settings and performance. Qualification welds can be performed on any welding method including wedge welding, extrusion welding, hand-held hot air welding, or bonded seam welding (which requires a curing time prior to testing). Two pieces of material, at least 1 m (3 ft) long are welded together and specimens tested. If the specimens meet project specifications then welding may proceed. If the specimens fail then the equipment is adjusted and re-qualified. Qualification welds are performed at the start of each welding period, when environmental conditions change significantly, when the welding machine is adjusted, or at the frequency required in the project specifications. The frequency of qualification welding is specified in Layfield’s Field QA manual.

Weld Samples

Weld samples are specimens removed from the geomembrane under construction to verify physical properties. Specimens are tested to project specifications. Seams not meeting specifications are repaired and retested as required. Layfield strongly recommends that the specimen removal sites be chosen so as not to require extensive repairs to the geomembrane. Specimens can be taken from the ends of seams, and from seams in the anchor trench. Layfield does not support the arbitrary destruction of a completed geomembrane seam in order to provide test samples. Cutting out a specimen from a completed wedge weld that has passed a non-destructive testing and is bound by two passed qualification welds does nothing to improve the performance of the geomembrane.

Non-destructive Testing

All field seams performed by Layfield are 100% non-destructively tested. There are different test methods available to test all types of geomembrane seams. Specific test methods are required for each geomembrane due to the physical properties of the geomembrane.

Air Pressure Test

The air pressure test is performed on seams prepared with a split wedge welding machine. The split wedge welder prepares two weld separated by an unbonded channel. This channel is sealed at both ends and pressurized. A drop in air pressure indicates an unbonded area which is then located and repaired. A seam that holds it pressure for the prescribed period indicates that the seam is fully bonded. The air is the released from the opposite end from where it was pressurized in order to verify that the tested seam is continuous. Details of the air pressure test ar in ASTM D5820.

Vacuum Box Test

The vacuum box test is performed on extrusion welds and welds on thick films and supported materials. The seam is flooded with soapy solution and a vacuum box placed over top. A vacuum is drawn on the box and the operator views the seam area through a viewing port. A stream of bubbles will indicate any discontinuities in the seam. Defects are marked and repaired. The vacuum box test is detailed in ASTM D5641.

Air Lance Test

For welds prepared in thin films, or in seams prepared with a solid wedge welder, an air lance test may be appropriate. An airl lance directs a nozzle of compressed air at the seam overlap. Any through defects will show as an inflated channel through the seam. Defects are then marked and repaired. The air lance test is detailed in ASTM D4437.

Point Stress Test

In certain areas such as around pipes and protrusions, it may not be possible to use one of the standard non-destructive test. In this case a point stress test may be called for. A point stress test uses a thin, blunt object to assist a visual inspection in determining that the seam is continuous. The point stress test is detailed in ASTM D4437.

 

16 Nov 2010 Testing Methods
Material Tests
High Density Polyethylene (HDPE) Destructive, Air Pressure, Vacuum Box, Point Stress
Polyvinyl Chloride (PVC) 20 and 30 mil Destructive, Air Lance, Point Stress
Polyvinyl Chloride (PVC) 40 to 60 mil Destructive, Air Lance, Point Stress, Air Pressure
Enviro Liner® Destructive, Air Lance, Point Stress
Polyproplyene (PP) Unsupported (U) Destructive, Air Lance, Point Stress, Air Pressure
Polyproplyene (PP) Supported (S) Destructive, Air Lance, Point Stress, Vacuum Box
Reinforced Polyethylene (RPE®) Point Stress
Geosynthetic Clay Liner (GCL) Visual Only
HAZGARD® Destructive, Air Lance, Point Stress, Vacuum Box
Arctic Liner® Unsupported (U) Destructive, Air Lance, Point Stress
Arctic Liner® Supported (S) Destructive, Air Lance, Point Stress, Vacuum Box
XR-5® Destructive, Air Lance, Point Stress, Vacuum Box
Specialty Liner (S) Destructive, Air Lance, Point Stress, Vacuum Box

If you require additional details on field testing methods please contact your Layfield representative.

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