| In the last half a century or so, pavement engineering has evolved from an art into a science. This has been made possible by the great advancements in many related fields of such as geotechnical engineering, engineering mechanics, material science, numerical modelling, computational techniques, instrumentation and techniques of measurement of pavement response to various kinds of loading. Despite these advancements, however, there exist significant gaps in our ability to analyze, evaluate and design pavements rationally. These gaps in our knowledge pertain to two areas: (1) Measurement of the mechanical properties of the materials in the pavement structure. (2) The models used for the analysis of pavements have many restrictive assumptions that make them too simplistic.; This thesis addresses these two questions in an attempt to fill this gap. The objective of this thesis is twofold: (1) To develop a finite element model to represent the pavement as a layered elastic solid with the minimum of restrictive assumptions. In fact the only restrictive assumption is that the problem is solved as an axi-symmetrical solid, (i.e) as a plane strain problem. The model should be able to consider any number of layers. It should be able to handle material properties such as non-homogeneity, non linearity, cross anisotropy and stress-dependency. (2) To adapt in-situ testing techniques that are common in geotechnical engineering to measure the properties of pavement materials directly as they exist in the ground. These can then be set directly into the model and pavement responses can be predicted.; In order to achieve these objectives the following tasks were undertaken and are reported in the thesis. (1) A multilayered elastic model was developed using a commercially available general purpose finite element program, ANSYS. This program turned out to be a powerful tool for such complex analyses. One unique feature of this algorithm is the ability to run an optimization routine which would lead to a match between the observed and computed deflection basins consistent with the measured material properties. (2) Five airfield pavements representing a wide range of subgrade, structural, environmental, loading and service lives were selected and tested with the Dynatest 8001 Heavy Weight Deflectometer/Falling Weight Deflectometer (HWD/FWD). (3) The pavements were cored at the test locations to ascertain the exact pavement structure and to recover materials for laboratory testing. (4) At the test location the moduli of the unbound layers were measured using the pavement pressuremeter developed by Briaud (1979). (5) The numerical model was used to backcalculate the moduli of the materials in the different layers within the bounds measured by the tests and specified in the model (see (1) above). (6) A regression analysis was carried out between the measured and the computed material properties at each site as well as by pooling all the data. (Abstract shortened by UMI.)... |
