Geomembrane Seam Failure and Welding Tests

Geomembrane is a geosynthetic product that is impermeable. In general, geomembrane must be seamed to prevent leaks at the overlaps, and geomembrane seam failure is a common cause of leakage. Geomembrane seams are divided into 3 types: Single Hot Wedge, Double Hot Wedge and Extrusion Fillet.

Geomembrane seam failure

Geomembrane seams can be damaged or fail. It is therefore important to know the types of seam damage so they can be avoided and leaks prevented.

Hot wedge seams have 2 types of seam failure:

• Adhesion failure – the 2 geomembrane layers fail to bond in the seam area.
• Break in seam – the geomembrane sheet breaks close to the seam area.

Geomembrane seam failure

Extrusion fillet seams have 2 types of seam failure:

• Adhesion failure – loss of adhesion to one of the geomembrane sheets.
• Break in fillet – failure of the seam bead (fillet).

Geomembrane seam failure

To check whether a geomembrane seam is sound, leak tests and seam strength tests (Shear Strength and Peel Strength) can be carried out. Leak tests are done in the field, while strength tests are done in a laboratory on samples/specimens taken from the geomembrane to be installed.

Geomembrane seam failure

For the shear test, the following equation can be used:

Formula

where:

E= elongation (≥ 50% for all seams)

L= elongation at break

Lo= gauge length (25 mm)

For the peel test, the following equation can be used:

Formula

where:

S= separation (≤ 25% for all seams)

A= average area of separation

Ao= original bonded area

The following reference table can be used to correlate test results: Table 1. Test value correlation for each HDPE geomembrane thickness

Geomembrane seam failure

The following are the types of geomembrane welding machines:

Geomembrane seam failure

Here is an explanation of each machine:

• LST 900 is a hot wedge welding machine for geomembrane with a thickness of ≥ 1 mm
• LST 800D is a hot wedge welding machine for geomembrane with a thickness of ≤ 1 mm
• Weldy EX3 is an extrusion fillet welding machine, used mainly for patching geomembrane
• Weldy HT1600 is a hot air blower welding machine