"Unbound Granular Materials (UGMs) are used in the base/subbase layers of flexible pavements for the majority of roads around the world. The deterioration of pavements increases with the increase of traffic loadings. To ensure the long-term performance and serviceability of pavement structures through a realistic design, the precise evaluation and comprehensive characterisation of the resilient and permanent deformation behaviour of pavement materials are essential. The present PhD study aims to investigate the characterisation of the resilient and permanent deformation behaviour of four road base UGMs sourced from quarries in Victoria, Australia, using Repeated Load Triaxial (RLT) testing. The triaxial system used in this study is instrumented with four axial deformation measurement transducers to achieve highly precise measurements and to evaluate the effect of instrumentation on the resilient modulus of UGMs. The resilient Poisson's ratio of the studied UGMs is also determined using a radial Hall-Effect transducer. Moreover, a series of permanent deformation tests is performed to precisely characterise the axial and radial permanent deformation behaviour of UGMs and investigate the factors that may significantly influence the accumulated axial and radial permanent deformations. Finally, three permanent deformation models incorporated with a time-hardening procedure are employed to predict the magnitude of permanent strain for multiple stress levels of the RLT test. The predictions using the employed models are then compared against the measured values to evaluate the suitability of the models and to identify the model that best predicts the strain accumulation behaviour of the tested UGMs. While this study focuses on the resilient and permanent deformation behaviour of four Victorian UGMs under repeated loading, the knowledge generated from this comprehensive investigation will contribute towards the global development of more reliable methods for evaluating the long-term performance of pavement structures and minimising road maintenance and repair costs." -- Abstract.