ASPHALT PAVEMENT DESIGN FOR ARIZONA

There is a general consensus that a procedure for the structural design of asphalt pavements must reflect considerations of the loads imposed, physical characteristics of the pavement layers, effects of the environment on those physical characteristics, definition of a layer failure, and a means for following changes in the load response of the pavement with time in service. The report presented is concerned with some of the details in developing and describing the proposed pavement design method. The pavement system is to be composed of three linear elastic layers--an asphaltic concrete surface, a granular base, and a subgrade. The modulus of elasticity and Poisson's ratio are of fixed values for the surface and base courses. These reference values are partially justified on the basis that both layers meet certain minimum requirements specified for their manufacture. The value for Poisson's ratio is also fixed for the subgrade; however, the modulus of elasticity is presently determined from correlation with test values such as CBR, R-value, and others. At the present, no definite procedure has been proposed to follow or detect structural changes in a pavement; however, the Dynaflect is being used to obtain deflection data. Recent analyses of Dynaflect deflections show lack of time-of-year effects on K1 values and suggest a need for modifying the measuring technique. A complete example of a pavement design is presented to illustrate the procedure.