Applying a Mathematical Model to the Calculations of Layer Moduli: In Relation to the Falling Weight Deflectomer

Abstract

Back calculations of layer stiffness are preceded by initial analyses of the deflection bowl in conjunction with the measured or assumed thickness of the layers. This step is important in understanding the strains, stresses, and moduli in the individual layers. An accurate modelling of the stiffness of the subgrade is observed to be important because a failure to achieve accuracy implies that disproportionately large errors are likely to arise during the back-analysis. Notably, the latter is applicable in for the provision of the upper layer moduli (State Highway Administration, 2016). With the existence of packages that aid in bob-linear subgrade analysis, the use of a system such as the ELMOD package uses deflections for calculating “n” and C. the relationship holds:E = C (σz/a’)n where n and C refer to constantsσz = vertical stressσ’ = reference stressE = modulus of elasticity