Dynamic Triaxial Testing of Unbound Granular Base Course Materials

摘要

The granular base and subbase layers in a flexible pavement play an essential role in the overall structural performance of the pavement. For better understanding, tests where in-situ stress conditions and traffic load are adequately simulated are needed. Repeated load triaxial testing (RLTT) is one such method. Here a constant confining pressure method (CCP method) has been used to evaluate the stiffness characteristics of typical Icelandic base course and subbase materials. A 150mm diameter specimen with a height of 300mm was used. So far the testing equipment has been used to evaluate the influence of different compaction levels as well as different moisture content on the mechanical properties. Based on the results it can be stated that different compaction levels clearly increased the stiffness for some materials. For others relatively little effects took place. One explanation could be that the effects of different compaction efforts during the building up phase of the specimen dwindled during the conditioning phase in the testing procedure. Moisture influenced stiffness behaviour. As the moisture content increased, stiffness increased. This was true when the degree of saturation was lower than approximately 80%. However as the degree of saturation neared full saturation, stiffness was reduced, and in some cases total collapse of the specimen occurred during the testing procedure.