Tests on Textured Geomembranes

Under the procedure of BAM certification of plastic geomembranes for landfill liners, special test methods and requirements have been specified for geomembranes with textured surface. Table A 1.4 in Appendix 1 shows the test procedures and requirements from the certification guidelines (Muller 2001), which aim to secure service lifetimes comparable to that of a smooth geomembrane. To what extent the requirements may be reduced if a shear stress transfer is required for only small or normal service lifetimes (see Table 5.1), is difficult to assess. 

An obvious challenge in testing of textured geomembranes manufactured by processes 1 and 3 is the determination of geomembrane thickness. The measurement of thickness cannot usually be performed using the standardised procedures described in Sect. 3.2.2. Sometimes individual test methods fitting to the special geometrical properties of a texture must be 

Usually no value for c is available and one only wants to control whether there is, for example, a 95 % chance that the trae mean value is above a certain specification. Assume that values of thickness measurements are normally distributed. Let fj. be the tme mean thickness of the geomembrane, m the measured mean value and s the standard deviation of a sample of an agreed upon number n of randomly taken specimen. (For example 10 specimens is a reasonable number.) The m-  

In impinged or laminated textures, attention must be paid to the uniformity of the texture. The distribution in the mass per area and in the form of the texture particle may not be so different along the geomembrane that 

If a texture geomembrane is installed on a steeply inclined external slope with some backfilling on top of it, where down-hill slope forces act continuously and permanent shear stresses and friction forces emerge in the geomembrane and in its interface to neighbouring components, it is in 

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Figure 3.25 illustrates typical displacement vs. time plots measured in the test on geosynthetic clay liners (Thies 2002 Muller et al. 2004). As shown by the graphs, an initial phase of rapid deformation (primary creep) in response to the compressive load is followed by a stable phase of gradual, continuous deformation (secondary creep). Shortly before failure, the speed of deformation increases sharply (tertiary creep or materials degradation) and failure occurs. Similarly to the pipe pressure test, these tests on textured geomembranes are carried out at 80 °C over a minimum of 10,000 h. 

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