Modified multiaxial tensile tests with geogrids in soil contact

For geogrids with the function "stabilization", the (low) deformability is one of the essential parameters. As a punctual wheel load is usually involved, the products are subjected to multiaxial loads. Therefore, one-directional tensile strip tests are not sufficiently meaningful for this application. A modified burst test is more likely to generate a multiaxial tensile load to geogrids. The geogrid is clamped in a circular ring and loaded by a spherically inflating membrane. The geogrid deforms into a spherical segment. This "multiaxial" tensile force-elongation behaviour can be evaluated and compared. The “multiaxial” test method has been further developed, while applying a gravel layer to the membrane (in a superstructure) and then tensioning the geogrid over it. This means that the geogrid is loaded by the ballast and no longer directly by the smooth membrane. Thus, any interaction effects between geogrid and gravel are also reflected, and the test approaches a so-called performance test. In principle, the evaluation is analogous to the test without gravel, but the measured values and diagrams reflect not only the ratio of load-deformation-stress, but also the interaction effects. Test setup, special features and evaluation are described and illustrated. The experiments and the results for three geogrids are presented and commented.