engleski

Influence of clamping conditions on tensile test results of geogrids

In this article results of tensile test for three types of geogrids are compared. They are tested in three different clamping conditions. First geogrids were tested without lining, in steel clamps, and then rubber and cork were used as lining. Tensile tests are performed according to the standard HRN EN ISO 10319. Increased values for tensile strength in laboratory tests can be obtained by using different types of lining for clamps, by which the rigidity of the surface holding the sample is reduced. Such behaviour of material can be explained that for most of the geogrid types, the ribs have a certain thickness, and are manufactured by a process where the threads are intertwined around the rib axis. When applying the tensile stress to the material, ribs get stretched in a manner that the threads first get straightened, and then stretched. By clamping the sample in steel clamps, the described behaviour of the geogrid material is completely prevented, while when the less rigid lining was used, it is possible to certain extent. Such stretch does not represent pulling the material out of the clamps. Because of the rigid grip of the steel clamps, the material will break in their immediate vicinity. By comparing the laboratory test methods for geogrids with the situation in the filed, it can be stated that less rigid lining better simulates the situation in the field. I.e. the granules of the stone material, over which the load is transferred to the mounted geogrids, do not press the grid absolutely rigidly, as does the steel lining. The laboratory tests must be as realistic as possible when simulating behaviour of a material used in a real life construction. Thus, real life situations should be simulated by using different liners for clamps.

tensile test; clamping conditions; geogrids

nije evidentirano