No description available.

No description available.

The current economic situation has severely affected the US road infrastructure and funding has become inadequate for either maintenance or future growth. The inverted base pavement structure is a promising alternative to achieve high quality roads at considerably lower cost than conventional pavements. The proximity of the unbound granular base layer to the tire load makes the response of the granular base critical to the performance of the pavement structure. Therefore extensive material characterization is conducted on the granular materials that make the base. In particular, a true triaxial chamber is developed to study the mechanical response and the stress-dependent stiffness of granular bases compacted at different water contents. A novel method is developed to assess the as-built stress-dependent anisotropic stiffness of granular bases in-situ using both crosshole and uphole test configurations. The two inverted base pavements built in Georgia at the Morgan County quarry haul road and the Lagrange south Loop are tested as part of this study. A nonlinear orthotropic constitutive model is selected to capture the deformational behavior of compacted granular bases. The response of the pavement is analyzed by implementing this constitutive behavior in a three-dimensional finite-element model. Different pavement structures are simulated. It is shown that thin asphalt concrete layers resting directly on granular bases deform as membranes. Finally, numerical simulations are extended to compare inverted base pavements to conventional pavements used in practice. Results highlight the inadequacy of ASSHTO’s structural layer coefficient for the analysis of inverted base pavement structures as well as the potential economic advantages of inverted base pavements.

No description available.

No description available.

Perpetual pavement design philosophy provides a long-life pavement design alternative. The ability of a pavement design to perform as long-life pavement is subjected to several technical constraints. Throughout the past 10 years, perpetual asphalt pavement designs have been under investigation in several parts of the world. The Canadian climate represents an additional challenge to the success of long-life pavement performance. This project investigated the construction and performance of three pavement test sections that were constructed on Highway 401 in Southern Ontario. The construction phase of this project was completed in 2010. The test sections were equipped with various sensors to monitor the structural performance. The test section included two perpetual pavement sections and one conventional pavement section. The two perpetual pavement designs were identical with the exception of the bottom asphalt layer, which was constructed as a Rich Bottom Mix (RBM) layer in one of the perpetual sections. The three pavement sections were evaluated from a structural point of view through the analysis of the in-situ tensile strain collected from asphalt strain gauges installed at the bottom of asphalt layers under the wheel path. In addition, asphalt material laboratory characterization was undertaken by testing asphalt samples collected during construction of the three test sections. The laboratory testing was performed at the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo. The laboratory experimental matrix in this research included dynamic modulus testing, resilient modulus testing and Thermal Stress Restrained Specimen Testing (TSRST). The correlation between various laboratory test results and the collected in-situ tensile strain was evaluated. Several linear regression models were developed to correlate the laboratory test results and the field asphalt temperature with the in-situ tensile strain. Overall, it was found that the perpetual pavement with RBM section had the lowest tensile strain at the bottom of asphalt layers. Also, various models were developed that predict tensile strain at the bottom of asphalt layers by using laboratory test data. An economic analysis was implemented to evaluate the perpetual and conventional pavement designs including a Life Cycle Cost Analysis (LCCA). Furthermore, a sustainability assessment for both design philosophies was executed to evaluate the environmental benefits of perpetual pavement designs. The perpetual pavement designs were shown to provide many benefits over the conventional asphalt pavement designs for usage on Canadian Provincial and Interstate Highways in similar climatic zones with similar traffic loading. The advantages of perpetual pavement design philosophy are not limited to structural benefits, but also extended to economic and environmental benefits in the long term.

The emergence of analytically-based pavement design has encouraged investigations toward a better understanding of the behaviour of pavement layers under cyclic loading. Unbound granular base (UGB) materials are commonly placed as base course layers in the design of pavement foundations. Due to their nature and geometry they are unsaturated geo-materials and therefore, it is desirable to study their behaviour using the framework of unsaturated soil mechanics. Current literature reflects very limited achievements in this direction. This thesis presents the development of a cyclic triaxial testing system and associated testing methodology that meets the challenges of testing an UGB material as an unsaturated soil. The testing system enables the initialisation of a specimen to target matric suction and facilitates direct measurement of its evolution under cyclic loading. In conjunction with the use of accurate on-specimens strain measurement transducers, ???clean??? strain and matric suction cyclic responses are obtained. Two types of cyclic triaxial testing are investigated: with constant cell pressure (i.e., CSeries testing) and with varying (cyclic) cell pressure where both axial and radial stress components are simultaneously (and in phase) pulsed (i.e., V-Series testing). Different initial matric suctions, si will be imposed in the testing program and the influence of si on material behaviour is analysed. This is investigated in a similar manner for C- and V-Series testing. The influence of si appears to be significant for both cyclic and permanent strain responses. A strong stress path dependency is found to characterise the behaviour of the UGB material. Under a wide range of cyclic deviator stress magnitudes, permanent strain response is found to correlate with that of matric suction response. Both appear to indicate better the relative performance of a UGB material than the response of resilient modulus. Another particular aspect investigated is the influence of additional fines on the behaviour of the UGB material. To ???isolate??? the effects of additional fines the cyclic and permanent strain responses of ???equivalent??? specimens with equivalent compaction and unsaturation condition, but different fines content, are compared. The results showed that the relative performance of the two materials (distinguished by the different percentage of fines content) in intertwined with the strong stress path dependency. It is also found that a material compacted at higher dry density may not improve its behaviour under cyclic loading, but may worsen with load cycles. Soil-water characteristic curve tests are conducted for the UGB materials investigated, showing high sensitivity of initial matric suction to moisture content, which increases further for the material with additional fines. This explains the notion of ???sensitivity??? of UGB materials as commonly suggested by practicing pavement engineers.

Thesis (M.S.) in Civil Engineering--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 191-197).

Thesis (M.S.) in Civil Engineering--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 131-135).

Thesis (M.S.)--Air Force Institute of Technology, 2007. / AFIT/AFIT/GEM/ENV/07-M4. "March 2007." Title from title page of PDF document (viewed on: Nov. 28, 2007). Includes bibliographical references (leaves 105-106).