Closed-form back-calculation of rigid-pavement parameters

This paper describes the development of a solution of surface deflections for the problem of infinite-slab-on-elastic foundation and its use in back-calculation analysis. Numerical integration is employed to compute the surface deflections. The method adopted simplifies calculations and leads to easy application in back-calculation of rigid-pavement parameters. A microcomputer closed-form back-calculation program called NUS-BACK is developed for this purpose, using the surface deflections measured by nondestructive testing devices as input. A comparison is made between the proposed approach and a widely reported closed-form back-calculation algorithm called ILLI-BACK. The proposed closed-form back-calculation scheme presents a more general solution to the rigid-pavement-evaluation problem. NUS-BACK can be used with deflections measured by any type of nondestructive surface deflection measuring devices directly. A major advantage of NUS-BACK over ILLI-BACK is its superiority in handling deflection data with measurement errors. Numerical examples are presented to illustrate the differences between the two closed-form backcalculation solutions.