Evaluation and Calibration of a New Bearing Capacity Model

OBJECTIVES: The objectives of this study are to evaluate and calibrate a new design model that has been developed for analyzing the bearing capacity of flexible pavements constructed on soil subgrades. The major intent of the study is to validate and implement the new model. Computer software containing the programmed equations of the model has already been developed. Instructions and training will be provided as appropriate. BACKGROUND: Over the past three decades, research engineers at UK have been developing a model for analyzing the bearing capacity of flexible pavements resting on soil subgrades. In contrast to design approaches that are based on empirical methods, such as the 1960 and 1993 AASHTO methods, and numerical methods, such as layered elastic, finite difference, or finite element approaches (AASHTO 2002), the new approach is based on limit equilibrium and calculates the factor of safety against failure. The design approach provides a new and entirely different method for determining the stability of flexible pavements during early construction as well as after construction. Alternative designs can be determined rapidly from the new approach. The model makes use of the shear strengths of flexible pavements, aggregates, and soils. Wheel loadings are considered directly in the program. The approach can also be used to check design thicknesses obtained from the 1981 flexible pavement design curves (semi-empirical), currently used in designing flexible pavements. Potential flexible pavement designs resting on soil subgrades that may fail can be quickly identified. This study was recommended in an implementation plan of a recently completed research study (Research Report KTC- 05-211SPR- 238-02-lF, "Bearing Capacity Analysis and Design of Highway Base Materials Reinforced With Geofabrics") as a follow-up study. Field data of more than 500 pavement profiles are readily available to make the analyses. No new field data collection is necessary. FY 2007 PROPOSED WORK: It is anticipated that profiles will be collected and examined, graphical representation will be developed, and bearing capacity analysis initiated during the 2007 fiscal year. The goal is to validate the existing models for use on future projects. PROGRAMMED COST FY 2007: TOTAL ESTIMATED COST: $ 50,000 $200,000