Previous work at Plymouth has shown the deflected shape as measured by the Deflectograph can be used to estimate the thickness of surfacing. This thesis extends the earlier work to develop relations between deflected shape and the stiffness and thickness of pavement layers. A literature study has been carried out to identify the factors causing the deterioration of flexible pavements. The literature study also assesses the various pavement evaluation equipment that is available and describes various methods of analysis and the interpretation of the pavement surface deflection shape that have been proposed. The properties of the materials of the various layers of the flexible pavement have been reviewed. Various structural models of a pavement are considered and the study indicates that the finite element method provides a most accurate prediction of actual pavement response to a moving wheel load. A 3D finite element model of a flexible pavement has been produced and partially validated with data obtained from the TRRL. A Fortran Programe has been developed to convert absolute deflections predicted by the 3D model into equivalent Deflectograph deflections. The model has been used to carry out parametric study to establish appropriate relationships between the deflected shape and material properties of the pavement layers. Relationships have been established to determine the thickness, modular ratio and modulus of the pavement layers and its support subgrade from measurement of the deflected shape. An Analytical Pavement Evaluation and Design System has been set up based on the relationships. The system has been validated by comparing the material properties obtained from the laboratory testing with those predicted by the design model using the Deflectograph measurements obtained from local roads with measurement of layer thickness and subgrade strength measured in-situ.

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