Backcalculation Flowchart Measure of Convergence In some backcalculation programs, a range (minimum and maximum) of moduli are selected or calculated to prevent program convergence to unreasonable moduli levels (either high or low).ДЇigure 1. Most backcalculation analyses assume pavements to be continuous, homogeneous and intact. The objective of this paper is to develop an innovative backcalculation method to calculate pavement layer moduli based on traffic speed deflectometer (TSD) measurements and analyze factors influencing backcalculation results. Various methods have been employed within the various backcalculation programs to converge on a set of layer moduli which produces an acceptable error between the measured and calculated deflection basins. The backcalculation programs (i.e., Modulus, WESDEF, and ILL-BACK) and deflection basin parameter (DBP) method are typically used to gain the modulus of pavement layers 4, 5. The measurement of pavement surface deflections under moving loads can be used for evaluation of pavement structural condition. There are various error measures which can be used to make such comparisons (more on this in a subsequent paragraph in this section). This element simply compares the measured and calculated basins. Layered elastic computer programs are generally used to calculate a deflection basin. Backcalculating the pavement layer properties is a well-accepted procedure for the evaluation of the structural capacity of pavements. (2011) Backcalculation of Dynamic Modulus from FWD Deflection Data, Transportation Research Record: Journal. Pavement structural adequacy is often evaluated by calculating elastic modulus of each layer using the so-called backcalculation. These moduli are usually estimated from user experience or various equations. Backcalculation of Asphalt Pavement Properties. The seed moduli are the initial moduli used in the computer program to calculate surface deflections. (FHWA-RD-97 -083), Design Pamphlet for the Backcalculation of Pavement Layer Moduli in Support of the 1993 AASHTO Guide for the Design of Pavement. (2000) Small-scale dynamic devices for the measurement of elastic stiffness modulus on pavement foundations, Nondestructive testing of pavements and backcalculation of moduli: third volume, ASTM STP 1375, S.D. Includes all layer thicknesses and load levels for a specific test location. Includes the measured pavement surface deflections and associated distances from the load.

Pavement backcalculation modulus