Geomembranes are defined by EN ISO 10318 as: Geomembranes are waterproof and barrier type materials made of polymers as the basic raw material. Geomembranes are mainly classified into: low density polyethylene (LDPE) geomembranes, high density polyethylene (HDPE) geomembranes and EVA geomembranes. Geomembrane is a geotechnical impermeable material made of plastic film as an impermeable base material and compounded with nonwoven fabric.

Physical properties
Geomembrane is a geotechnical impermeable material made of plastic film as an impermeable base material and compounded with nonwoven fabric. Plastic films used for seepage control at home and abroad mainly include polyvinyl chloride (PVC) and polyethylene (PE), EVA (ethylene/vinyl acetate copolymer), and ECB (ethylene vinyl acetate modified asphalt blended geomembrane) designed for tunnel applications, which are polymeric chemically flexible materials with low specific gravity, high extensibility, high adaptability to deformation, corrosion resistance, low temperature resistance, and good frost resistance.

The main physical properties of geomembranes in the as-manufactured state are:

Thickness (smooth sheet, textured, asperity height)

Density

Melt flow index

Mass per unit area (weight)

Vapor transmission (water and solvent).（FR:WIKI)

Geomembrane permeability testing program
A roadway is a major highway for over 1,550 miles. The highway is prone to undulations in the sidewalk within 7 miles of the highway due to the presence of swelling clay under the roadway. As the moisture content of the clay increases, the clay tends to swell, which results in uneven expansion and contraction. The moisture content of the area changes frequently depending on weather conditions, and the situation is further complicated in the summer by drastic temperature changes between 18°C and 43°C in winter. These undulations have a negative impact on the pavement and, as a result, several repairs have been required in the area since the construction of the period.
A long-term solution was now sought to maintain the problematic soil. The final choice was to use a geomembrane with a strong moisture barrier to control the swelling of the clay roadbed. The geomembrane minimizes the chance of significant moisture changes in the pavement bed, so the geomembrane needs to be tested for water barrier before it is put into service
Test procedure
(1) Cut 3 specimens from the surface of the geomembrane sample with the sampler.
(2) Add a certain amount of distilled water to each of the 3 permeable cups and clamp the 3 specimens in each of the 3 permeable cups to ensure a good seal between the specimens and the permeable cups.

(3) Place the moisture-permeable cups with clamped specimens on the moisture-permeable cup holder in the test chamber of the equipment respectively, and close the door of the test chamber.
(4) In the system software part, set the specimen thickness, test temperature and humidity (38℃, 90% RH), test time interval and other parameters information, click the test option, the test begins. Equipment automatically according to the set time interval test the weight of the moisture permeability cup, according to the test data, calculate and display the water vapor transmission rate of the specimen and other test results.
Test results
The test results of the three specimens measured in this test were 0.11 g/(m2-24h), 0.67 g/(m2-24h), and 0.09 g/(m2-24h), respectively. The water vapor transmission rate of the waterproof breathable membrane sample used in this geomembrane was taken as the average of the three specimen test results of 0.29 g/(m2-24h). Therefore the geomembrane made of flexible sheet of this polymer is a low permeability barrier.
The waterproof permeable membrane is an important component of geomembranes, which has the characteristic of preventing urine water leakage and has an important impact on the water barrier of geomembrane use. The water vapor permeability performance of a geomembrane sample was verified by testing the water vapor transmission rate of the sample. Understanding the permeation requirements of an application and specifying the best geomembrane can be challenging as different geomembranes have different failure mechanisms. It is recommended to look at the overall application and investigate the permeability performance, and life expectancy of the geomembrane and any other factors that will affect the application prior to selection.