Microcomputer Based Procedure for Backcalculating Layer Moduli from FWD (Falling Weight Deflectometer) Data

摘要

The report describes a backcalculation procedure (MODULUS) developed to interpret Falling Weight Deflectometer (FWD) data and illustrates how the procedure was built into a pavement analysis system for the Texas State Department of Highways and Public Transportation. MODULUS is microcomputer based and can be used on 2-, 3-, or 4-layer pavement systems. It uses a linear-elastic program to generate a database of deflection bowls; in a four-layer system, a minimum of 27 runs (3 x 3 x 3 moduli values for surface, base, and subgrade) would be performed. The size of the database depends on the user-supplied range of acceptable modulus values for each layer. Once the database is generated, a pattern search routine is used to fit measured and calculated bowls; error minimization is very rapid, less than 5 seconds per bowl on a 386-type microcomputer.