THE USE OF FWD DEFLECTION DATA IN MECHANISTIC ANALYSIS OF FLEXIBLE PAVEMENTS . THIRD INTERNATIONAL CONFERENCE ON BEARING CAPACITY OF ROADS AND AIRFIELDS. PROCEEDINGS, NORWEGIAN INSTITUTE OF TECHNOLOGY, TRONDHEIM, NORWAY, JULY 3-5 1990. VOLUMES 1-2

This paper describes research which compares the values of elastic modulus measured in situ by a falling weight deflectometer (FWD) with those obtained by a newly developed backcalculation program LMBS. Four pavement test sections, each with different structures were constructed in a national highway near Tokyo. FWD deflection measurements were carried out at several points on the pavement surface under 49 kN load and with no correction for temperature. The LMBS Program, which incorporates the multilayer elasticity program ELSA, requires the thickness and Poisson's ratio of each pavement layer, the wheel load, and the contact pressure of the tyre in order to carry out backcalculations. Because the influence of Poisson's ratio on the deflection is very small, a sensitivity analysis was conducted to evaluate the influence of a change in surface deflection and layer thickness upon the calculated elastic moduli. The in-situ moduli calculated using the FWD deflection data at each construction stage are compared with one another to confirm the validity of the backcalculation method. (TRRL)