CLOSED-FORM BACK-CALCULATION OF RIGID-PAVEMENT PARAMETERS

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