Effect of Depth to Bedrock on the Accuracy of Backcalculated Moduli Obtained with Dynaflect and FWD Tests

摘要

Analytical simulations of the Dynaflect and Falling Weight Deflectometer (FWD) tests were performed on four typical in-service pavement profiles (three flexible pavements and one rigid pavement). Stiffnesses of the pavement surface layer, base, subbase, and subgrade were varied over ranges typical of in-service pavements. Depths to bedrock below the pavement surface varied from a few feet to over 100 feet (30 m). The effect of depth to bedrock (also referred to as the 'dynamic' effect) was expressed in terms of deflection ratios ('dynamic' deflections divided by static deflections). 'Dynamic' deflections represent those deflections which are actually measured when these tests are performed on pavements. The amplitude of the deflection ratio is an important index of the potential error generated in any static interpretation procedure. The results show that the stiffness of the subgrade has the most significant effect on the maximum amplitude of the deflection ratio (deflection ratio at resonant conditions). The softer the subgrade, the higher the amplitude of the maximum deflection ratio. This behavior agrees with the trend in backcalculated layer moduli using static interpretation programs.