designing a mathematical model for predicting the mechanical characteristics of asphalt pavements using dynamic loading

the available methods for predicting mechanical characteristics of pavement layers are categorized into two general groups, destructive and non-destructive. in destructive method, using coring and pavement subgrade and performing necessary experiments on them, the quantities of layers properties will be identified. in non-destructive method, the attained deflection is measured by applying the loading on pavement surface using equipments such as fwd which charges the impact dynamic load, and the mechanical characteristics of pavement layers are determined using back calculations. the procedure of conducting these calculations is that by knowing the thickness of the pavement layers and assuming the initial amounts for mechanical characteristics of the layer, the attained deflection at the desired points on the pavement surface will be calculated. then, new figures are assumed for the characteristics of layers in a reattempt and calculations are repeated again. this trial and error is continued until the produced basin deformations from the calculations with true value, differs in an acceptable range. using this method may have no accurate and single answer, since the various compositions of layers characteristics can produce similar deformations in different points of pavement surface. in this article, using an innovative method, a measurement is taken in constructing and introducing a mathematical model for determining the elastic module of surface layer using deflections attained from fwd loading equipment. the procedure is such that by using dynamic analysis software of finite elements like abaqus and ansys, the deformation of corresponding points on the surface of the pavement will be attained by fwd loading equipment. this analysis will be performed on a number of pavements with different thicknesses and different layers properties. the susceptibility analysis of different points deformations show, which will be performed as a result of the change of properties and layers thicknesses. using this artificial data base as well as deflection basin parameters (dbp), a measurement will be taken toward constructing a regression model for determination of asphalt layer model, i.e. eac =f(dbp) function shall be attained. to achieve the maximum correlation coefficient, an attempt is made to use the parameters of deformations basin which has the most susceptibility in changing asphalt layer module.