![]() ![]() This element simply compares the measured and calculated basins. Layered elastic computer programs are generally used to calculate a deflection basin. These moduli are usually estimated from user experience or various equations. The seed moduli are the initial moduli used in the computer program to calculate surface deflections. Includes all layer thicknesses and load levels for a specific test location. Includes the measured pavement surface deflections and associated distances from the load. Typical FlowchartĪ basic flowchart (patterned after Lytton, 1989 ) that represents the fundamental elements in all known backcalculation programs is shown as Figure 1. The backcalculation process is usually iterative and normally done with computer software. The combination of assumed layer stiffnesses that results in this match is then assumed to be near the actual in situ moduli for the various pavement layers. The assumed layer moduli in the calculated model are adjusted until they produce a surface deflection that closely matches the measured one. Backcalculation takes a measured surface deflection and attempts to match it (to within some tolerable error) with a calculated surface deflection generated from an identical pavement structure using assumed layer stiffnesses (moduli). “ Backcalculation” is a mechanistic evaluation of pavement surface deflection basins generated by various pavement deflection devices. ![]()
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