00625544

Component

http://onlinepubs.trb.org...trr/1992/1355/1355-006.pdf

https://scholar.google.co...Ruth&publication_year=1992

Theoretical analyses were conducted to illustrate the inability of the existing single-load falling weight deflectometer (FWD) to discriminate among near-surface layer moduli of flexible pavement systems. Comprehensive analyses were also conducted to show that this deficiency can be overcome by using a dual-load FWD when the loads are spaced sufficiently apart to induce a concave downward curvature in the pavement surface between the loads (transverse deflection basin). The analyses showed that the asphalt concrete modulus is strongly, and almost uniquely, related to the curvature of this trnasverse deflection basin, whereas the base course modulus is strongly, and almost uniquely, related to the shape of the longitudinal deflection basin. This strong correspondence was shown to hold true for a broad range of pavement geometries and layer moduli. Stress and deformation analyses were conducted to show that the dual-load system works because the shape of the transverse deflection basin is most strongly influenced by the bending moments induced within the asphalt concrete layer between the loads, and by the relatively large changes in vertical compression that are induced in the asphalt concrete layer within this zone. Neither of these effects is observed in the base course, which explains the lack of influence of the base course on the shape of the transverse deflection basin. Finally, an analysis was conducted to select load radii and spacing, and deflection sensor positions that optimize the capabilities of a dual-load system to discriminate among near-surface layer moduli. It was shown that a set of relatively simple equations can be developed to determine (backcalculate) pavement layer moduli obtained from surface deflection measurements using the dual-load system proposed.

This paper appears in Transportation Research Record No. 1355, Nondestructive Structural Evaluation of Pavements. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

01405034

English

p. 52-58

1992

Transportation Research Record

030905219X

Figures (15) ; References (3) ; Tables (1)

Asphalt concrete; Backcalculation; Bending moments; Equations; Falling weight deflectometers; Flexible pavements; Layer coefficient (Pavements); Modulus

Layer moduli

Data and Information Technology; Design; Highways; Pavements; I22: Design of Pavements, Railways and Guideways; I23: Properties of Road Surfaces

TRIS, TRB, ATRI

Dec 16 1993 12:00AM

• ALTERNATIVE METHOD FOR TEMPERATURE CORRECTION OF BACKCALCULATED EQUIVALENT PAVEMENT MODULI
• COMPREHENSIVE EVALUATION OF FIVE SENSORS USED TO MEASURE PAVEMENT DEFLECTION
• EFFECT OF DEPTH TO BEDROCK ON DEFLECTION BASINS OBTAINED WITH DYNAFLECT AND FALLING WEIGHT DEFLECTOMETER TESTS
• EFFECTS OF BUFFERS ON FALLING WEIGHT DEFLECTOMETER LOADINGS AND DEFLECTIONS (WITH DISCUSSION)
• ESTIMATING DAMAGE EFFECTS OF DUAL VERSUS WIDE BASE TIRES WITH MULTIDEPTH DEFLECTOMETERS
• FIELD AND LABORATORY DETERMINATION OF ELASTIC PROPERTIES OF PORTLAND CEMENT CONCRETE USING SEISMIC TECHNIQUES
• MODELING OF GROUND-PENETRATING RADAR WAVE PROPAGATION IN PAVEMENT SYSTEMS
• NONLINEAR EFFECTS IN FALLING WEIGHT DEFLECTOMETER TESTS
• RADAR PAVEMENT THICKNESS EVALUATIONS FOR VARYING BASE CONDITIONS
• SIMPLIFIED, RATIONAL APPROACH TO FALLING WEIGHT DEFLECTOMETER DATA INTERPRETATION
• VARIABILITY IN ESTIMATION OF STRUCTURAL CAPACITY OF EXISTING PAVEMENTS FROM FALLING WEIGHT DEFLECTOMETER DATA