Geotextiles in Embankment Dams - Association of State Dam Safety ...

Chapter 2—Overview of Geosynthetics for Use in Embankment Damssteel rod punctures the geotextile which is clamped firmly to the end of a 45-mmdiametersteel cylinder. Although used as an index QC test, the small diameter rodgives much variability in lighter fabrics. ASTM D 6241 was developed based on a 50mm diameter puncture probe (California Bearing Ratio (CBR) test probe) and is nowcommonly used also as a QC test method. Additionally, due to the large punctureprobe size, there is a direct relationship between wide width (ASTM D 4895) tensilevalues and CBR puncture values.Puncture – Hydrostatic Vessel (ASTM D5514) – a large scale performance testwhere geotextiles are used as cushions beneath geomembranes. Puncture resistancecan be determined in 500-mm diameter hydrostatic pressure vessels using actual testsoils or rock. The geotextile is placed between the test soil and the geomembrane tobe protected. The test fluid (usually water) is then placed over the geomembraneand the test pressure is increased until the geomembrane ruptures.Friction or Interface Shear – Large Scale Performance Direct Shear Tests (ASTMD5321) use a 12- x 12-inch soil box to measure the frictional properties between thegeotextile and site-specific soil, or between the geotextile and another geosynthetic.As this is a true performance test, the method can model soil type, density, loadingand anticipated strain rates.Pullout Resistance – (ASTM D6706) - A large scale performance test for geotextilesused to provide anchorage for reinforcement applications. The geotextile is usuallysandwiched with soil on either side. The pullout test greatly resembles the directshear test and provides the user with a set of design values.2.12.3 Hydraulic propertiesPorosity – (ASTM D6767) is the ratio of the void volume to the total volume.Porosity is typically calculated from other geotextile properties as follows:n = 1-m/ptn = porosity (dimensionless)m = mass per unit area (g/m 2 )ρ = rho = density (g/m 3 )t = thickness (m)Pore size distribution can be derived using ASTM D6767 which tests pore size bycapillary flow.45