Geomembrane Installation Steps and Weld Testing

Geomembrane Installation Steps:

1.0 Subgrade Preparation — The geomembrane installation steps begin with subgrade preparation.

The subgrade where the geomembrane will be installed must be level and free of sharp objects. All gravel and roots must be cleared from the work area. A geotextile or protective layer can help keep the geomembrane safe from leaks caused by objects in the project environment.

In areas with organic soil or peat, an underdrain and pressure-release system must be provided to prevent gas bubbles from forming beneath the geomembrane.

A geomembrane anchor trench must be provided around the entire geomembrane area. The ideal trench dimensions are 24” ( 60 cm) deep and 12” ( 30 cm) wide.

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2.0 Panel Measurement

The area to be covered by the geomembrane must first be measured, then the panel must be cut to fit the dimensions of the area to be lined.

3.0 Weather

Geomembrane installation cannot be performed in rainy conditions.

4.0 Installation Method

The methods, personnel and workers must not damage the subgrade. All operators must wear footwear that will not damage the geomembrane.

5.0 Geomembrane Welding

Geomembrane welding is performed by placing a hot-wedge machine between the overlapping panels. The machine heats the geomembrane until it melts, then presses the sheets together to form a single unit.

 

Geomembrane installation video

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The overlap between panels must be at least 4 inches (10 cm), and the geomembrane surface must be free of dust, dirt or moisture that could interfere with the welding process.

Weld Test Results

6.1. Vacuum test

a. Apply soap solution to the area where the membrane quality will be checked.

b. Place the vacuum box on the membrane surface. Make sure the rubber seal is fitted beneath the box to ensure an airtight seal.

c. Open the vacuum valve and apply a vacuum pressure of 4 psi.

d. Monitor for 10 seconds to see whether air bubbles form inside the vacuum box.

e. If air bubbles form, mark the area for repair.

6.2. Air pressure testing

A hot-wedge machine creates an air channel in the weld, as shown below.

Air pressure is injected into the channel to confirm that it remains stable for a specified period. The test must comply with ASTM D-5820.

Procedure:

1. The initial pressure must be set to a minimum of 20 PSI and a maximum of 25PSI.
2. Read the initial pressure after 2 minutes and inject air.
3. Wait for 5 minutes and make sure the pressure does not drop by as much as 4 psi. If the pressure is unstable, mark the geomembrane for repair.

7.0. Geomembrane Connections to Concrete & Pipes

ASTM D6479 governs geomembrane connections to concrete structures and pipes. The following diagrams show details of geomembrane connections to concrete and pipes.