00625540

Component

http://onlinepubs.trb.org...trr/1992/1355/1355-002.pdf

https://scholar.google.co...e+II&publication_year=1992

The dynaflect and falling weight deflectometer (FWD) are commonly used for nondestructive testing of pavements. In both cases a dynamic load is imparted on the surface of the pavement, and deflections are measured at various points along the surface. Evaluation of the moduli of the surface layer, base, and subgrade is normally performed by comparing the experimental deflections with the results of static analyses. The moduli of the layers in the static model are then varied in an iterative procedure until a reasonable match between experimental and theoretical deflections is obtained. This solution ignores the dynamic nature of these nondestructive tests. In this paper the effect of depth to bedrock on the amplitude of the deflections and the shape of the deflection basins obtained with the dynaflect and the FWD tests is investigated analytically. Dynamic and static deflections at four different pavement profiles are compared. The results show that the range of bedrock depths over which dynamic effects are important differs between the two nondestructive tests because of the excitation frequencies and depends mainly on the stiffness of the subgrade. The results also show that, when dynamic effects occur in the measurements but are not taken into account in the analysis, the modulus of the subgrade is generally underestimated, sometimes by 50% or more, and the moduli of the base and surface layer are overestimated. Finally, a simple method is suggested for the FWD that makes it possible to estimate the depth to bedrock by recording the free vibration of the pavement system.

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. 8-16

1992

Transportation Research Record

030905219X

Figures (6) ; References (9) ; Tables (3)

Bedrock; Coefficient of subgrade reaction; Deflection; Depth; Dynaflect; Falling weight deflectometers; Layer coefficient (Pavements); Modulus; Nondestructive tests; Pavements; Stiffness; Subgrade (Pavements)

Layer moduli

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
• EFFECTS OF BUFFERS ON FALLING WEIGHT DEFLECTOMETER LOADINGS AND DEFLECTIONS (WITH DISCUSSION)
• ESTIMATING DAMAGE EFFECTS OF DUAL VERSUS WIDE BASE TIRES WITH MULTIDEPTH DEFLECTOMETERS
• EVALUATION OF A DUAL-LOAD NONDESTRUCTIVE TESTING SYSTEM TO BETTER DISCRIMINATE NEAR-SURFACE LAYER MODULI
• 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