A PROCEDURE FOR THE ANALYSIS OF BENKELMAN BEAM DEFLECTION BOWLS --14TH ARRB CONFERENCE, 28 AUGUST - 2 SEPTEMBER, 1988, CANBERRA, ACT, AUSTRALIA; PROC. PARTS 1 - 8

In the past back analysis of deflection bowl results, to obtain estimates of pavement and subgrade strength parameters, has involved use of trial and error curve fitting techniques comparing measured rebound bowl shapes with predicted bowl shapes from elastic analysis programs. The US Corps of Engineers developed an iterative program utilising chevron to simplify this procedure. However, difficulties have been experienced in obtaining realistic estimates of pavement and subgrade stiffness particularly when analysing bowls from stiff (eg, cement treated) pavements. The cause of this has been that the measured bowl is not a true indication of the actual deflection bowl because of the influence of the bowl on the legs of the Benkelman beam. Attempts to correct the measured bowl for the influence of the actual bowl on the beam's legs have not been totally successful because a knowledge of existing pavement strength properties is required to make an accurate correction and it is these strength properties that are sought from the back analysis. This paper presents a procedure for back analysis of deflection bowls utilises the US Corps of Engineers iterative approach but calling in circly rather than chevron and using the geometry of a Benkelman beam to correct the computer predicted to obtain estimates of pavement and subgrade moduli, which deflection bowl to what would have been measured by a Benkelman beam. Although this procedure produces only minor differences in the analysis of bowls for granular pavements (where the effect of the bowl on the beam's legs is minimal) it gives major variations and more realistic results when analysing bowls measured on stiff pavements (a). For the covering record of the conference, see IRRD no 808936.