The total permanent deformation of flexible airfield pavements is one of the best indicators of the overall performance of the pavement system. A methodology was developed to predict this distress mode under aircraft loading on asphaltic concrete pavement systems. Particular emphasis is placed on the use of lateritic gravels intrinsicto many parts of brazil. Using dynamic triaxial tests in the laboratory, models based on the california bearing ratio, state of stress, and number of load repetitions were developed for estimating the resilient modulus and the plastic deformation of lateritic base, subbase, and subgrade layers. The permanent deformation for flexible airfield pavement design (pdapd) computer model was developed from modification of the existing asphalt institute dama program on the basis of multilayer elastic theory. The input variables necessary for thismodel come from three broad areas: the environement, the dynamic characteristics of the materials, and the traffic analysis. Pdapd, which can analyze up to 10-layer pavement structures, estimates the pavement damage on a monthly basis considering three criteria: fatigue of asphalt concrete layers, subgrade deformation, and total permanent deformation of the pavement. General verification of the pdapd wasaccomplished by a computer analysis of numerous flexible-pavement airfield structures, designed in accordance with the faa method. Although individual pavement section results varied, a good overall comparison in design life prediction occurs between the empirically based faa approach and the mechanistic pdapd model. This paper appears in transportation research record no. 1307, Pavement analysis, design, rehabilitation, and environmental factors 1991.
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