Moisture Sensitivity of the Deformation Properties of Unbound Granular Materials

Abstract

A series of Repeated Load Triaxial (RLT) tests was carried out on a typical Unbound Granular Material (UGM), used as base layers in thin flexible pavements. The tests were performed with different moisture contents to enhance the understanding of the effect of moisture on the deformation properties that may be used for future modeling and design. The grain size distributions of the materials were altered to study the effect on the moisture sensitivity. The influence of moisture on the resilient deformation properties was investigated using the resilient test protocol from the European standard. An existing stress dependent resilient modulus (MR) model was calibrated using the test data and the variation of the model parameters with moisture was investigated. The parameters of a moisture-dependent MR model were also studied for their dependency on the grain size distribution. The multi-stage (MS) loading approach according to the European standard was used to obtain information about the influence of moisture on the permanent deformation characteristics. Results indicate that both the resilient and permanent deformations increase with increasing moisture content. These effects are more pronounced for materials with finer grading.