Standard Test Method for Evaluation of Hydraulic Properties of Geosynthetic Clay Liners Permeated with Potentially Incompatible Aqueous Solutions

Importancia y uso:

4.1 This test method applies to one-dimensional, laminar flow of aqueous solutions, such as chemical solutions, landfill leachate, and contaminated water (from here on referred to as “test liquid”), through saturated/hydrated GCL specimen that is consolidated and permeated under a prescribed or requested set of conditions.

4.2 This test method assumes that Darcy’s law is valid and that the hydraulic conductivity is essentially unaffected by hydraulic gradient. The validity of Darcy’s law may be evaluated by measuring the hydraulic conductivity of the specimen at three different hydraulic gradients; if all measured values are similar (within about 25 %), then Darcy's law may be taken as valid. However, when the hydraulic gradient acting on a test specimen is changed, the state of stress will also change and, if the specimen is compressible, the volume of the specimen will change. Thus, some change in hydraulic conductivity may occur when the hydraulic gradient is altered, even in cases where Darcy's law is valid.

4.3 This test method provides tools for determining flux and hydraulic conductivity values for a given GCL under the following two different scenarios, which should be specified by the requester:

4.3.1 Scenario 1 – Hydrated/Saturated with Water Prior to Contact with Test Liquid—This scenario simulates the field conditions where the GCL is well hydrated with water prior to contact with actual test liquid. It should be noted that initial degree of saturation/hydration greatly affects the hydraulic properties of a GCL product. The test has two phases: (Phase 1) hydrate, saturate, consolidate, and permeate with water as Test Liquid 1, and (Phase 2) switch to permeation with test liquid as Test Liquid 2.

4.3.2 Scenario 2 – Hydrated/Saturated with Test Liquid (Worst Case)—This scenario simulates the field conditions where the GCL is in contact with test liquid prior to being fully hydrated with water. It should be noted that this scenario may result in higher flux and hydraulic conductivity values compared to Scenario 1, as chemicals present in test liquid may alter the hydration and hydraulic properties of a GCL product.

4.4 The apparatus used in this test method is commonly used to determine the hydraulic conductivity of soil specimens. However, flux values measured in this test are typically much lower than those commonly measured for most natural soils. It is essential that the leakage rate of the apparatus in this test be less than 10 % of the flux.

Subcomité:

D35.04

Referida por:

D6141-18R22

Volúmen:

04.13

Número ICS:

59.080.70 (Geotextiles)

Palabras clave:

coefficient of permeability; geosynthetic clay liners (GCLs); hydraulic barriers; hydraulic conductivity; liners; permeameters;