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Evaluation of accelerated rut development in unbound pavement foundations and load limits on load-zoned pavements
xxiv, 301 leaves : illustrations ; 28 cm.
Load-zoned pavements in Texas are presently posted using gross vehicle weight (GVW) limits to prevent or minimize the development of permanent deformation due to excessive truck loads. In reality, pavement damage is more related to axle loads and axle configuration than with GVW. Thus, load restrictions should be related to axle loads, axle type, pavement structure, and material characteristics. It is for this purpose that the non-linear finite element program (FERUT) has been developed. Stress dependent models for the resilient modulus and Poisson's ratio of the unbound foundation materials are incorporated into the finite element model to predict the resilient behavior within the pavement layers under specified traffic loads at a given seasonal condition. The structural adequacy of pavements is predicted using the Mohr-Coulomb failure criterion. Results of the predicted resilient strains are combined with the VESYS and the Three Parameters models. Integrating the permanent deformation of each layer results in the overall rutting and layer rutting in a pavement structure under a given trafficking period. Of the stress dependent resilient parameters, the k1 parameter results in the most significant changes to the predicted pavement responses. However, the effects of the non-linear resilient k2 and k3 parameters depend significantly upon the interactions between parameter values, applied loads, and pavement geometry at a given traffic level. Rutting predictions have been studied, and the results correlate well with actual rutting performance data from the Texas Mobile Load Simulator (TxMLS) field tests. The non-linear finite element program developed can accurately predict layer rutting in unbound pavement foundations. No tension is predicted using the stress dependency approach in an unbound base layer. In addition, the framework for predicting accelerated rut development on pavement foundations is proposed by the use of the principles of unsaturated soil mechanics. Permanent deformation of the pavement foundation materials is characterized in the laboratory, and regression equations are developed for those parameters of the VESYS and the Three Parameters models. A methodology for posting or removing load limits is formulated for a specified pavement route based on the axle load limits. In conclusion, this study demonstrates that the framework proposed for load zoning is rational and based on engineering principles accounting for the effects of vehicle and pavement factors.
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 277-291).