Modeling Of Rutting Prediction For Flexible Pavements In Zambia

The core road network (CRN) infrastructure in Zambia is estimated at40,113kmconsisting of (60%) paved and (40%) unpaved. The current estimates of the level of servicefor paved road network is25%good,35%fair and40%poor based on the internationalroughness index (IRI) scale of IRI <4.5,4.5<IRI <9and IRI>9m/km respectively, whileunpaved road network is at10%good,11%fair and79%poor. Road transportation ofgoods and services for export to neighboring gulf countries combined with high temperatureenvironment, poses a high influence on the level of service of hot mix asphalt pavementsmanifested through severe rutting damage. This situation causes a huge impact on roadoperation services, therefore, research on the prediction of rutting damage on asphaltpavements is necessary to improve the operation services of our roads.Focusing on Zambia’s special tropical climatic conditions, finite element analysistools are used to model and predict permanent deformation and performance evaluationconducted. Falling weight deflection tests conducted on a45kilometers flexible pavementare, analyzed for temperature and seasonal humidity environmental factors by backcalculation computational techniques by determining their effect on five different pavementstructures layer modulus of elasticity. Master curves are determined through time-temperature superposition principle, and analyzes the effects of temperature changes to thedesign of pavement overlay mixture based on the residual service life and materialparameters for finite element model determined from indoor laboratory experiments.Results show that back calculation computational techniques on field falling weightdeflection measurements provides reliable pavement under layers material characteristicsinput parameters for the finite element model. Permanent deformation results of ruttingprediction from the mobile load simulator experiment provided verification and evaluationdata for finite element models. Creep and visco-elasto-plastic models measured ruttingprediction results and developmental conditions are consistent with mobile load simulatormeasured values. It can be seen from the evaluation of rut prediction in the representativesections that weak subgrades on Zambia’s pavement is one of the main causation factors forrutting.Based on the testing process and method of characterization of pavement materialperformance used in this research, valuable future suggestions are provided for the countryas it is undergoing a transition from empirical pavement design to mechanical-empirical methods. Through conducting accelerated mobile load simulator test in the field, the rutprediction models can be calibrated by using the actual field rutting deformation parameters.