SUITABILITY OF USING THE FALLING WEIGHT DEFLECTOMETER IN DETERMINING DETERIORATED AREAS IN JOINTED RIGID PAVEMENTS

In this study the suitability of using the falling weight deflectometer (FWD) to determine deteriorated areas in rigid pavements was investigated. The FWD deflection basins of a few hypothetical concrete pavements of three types of deficiency conditions were calculated by using the finite-element analysis computer program WESLIQUID. These computed deflection basins were then compared with the deflection basin of a reference pavement that was in good condition. The three types of deficiency conditions studied were pavements with (a) weak subgrades, (b) voids in the subgrade beneath the concrete slab, and (c) deteriorated concrete slabs. Two FWD loading positions were considered: loading at the center of a pavement slab, and loading near the joint of the slabs. The results of the study indicate that the three different types of concrete pavement distress give three distinctly different FWD deflection basin shapes. The distinction among these three types of FWD deflection basins can be more easily understood by considering the differences between the FWD deflection of the pavement considered and that of a standard pavement of the same dimension that is loaded at the same position (D-Ds). The type and extent of the pavement distress could be determined from the shape and the magnitude of the D-Ds plot. The results of the study also indicate that the effects of the joint are insignificant when the applied FWD load is far away from the joint.