Review of the Long-Term Pavement Performance Backcalculation Results—Final Report

摘要: A new approach to determine layered elastic moduli from in situ load-deflection data was developed. This "forwardcalculation" differs backcalculation that modulus estimates come directly the load and deflection using closed-form formulae rather than iteration. The forwardcalculation equations are used for subgrade bound surface course both flexible rigid pavement falling weight deflectometer (FWD) data. Intermediate layer estimated through commonly modular ratios between adjacent layers. entire Long-Term Pavement Performance (LTPP) set of backcalculated parameters screened forwardcalculated moduli. Any assumed or fixed value left as is not further (e.g., hard bottom). Further, any back- values outside a broad range reasonable were screened, but flagged unreasonable. Finally, convergence flags (0=acceptable, 1=marginal, 2=questionable, 3=unacceptable) applied dataset, depending on how closely pairs matched. Since techniques identical FWD input, derived each should be reasonably close other (within factor 1.5 qualify acceptable, example). Although cannot rejected merely because they acceptable range, complementary usually more stable section-by-section basis. exception portion database based slab-on-dense-liquid slab-on-elastic-solid theory, where correspondence two approaches excellent very stable. Therefore, it recommended retained is, with addition checks so user can choose best method, application.