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ERIC Number: ED526002
Record Type: Non-Journal
Publication Date: 2009
Pages: 438
Abstractor: As Provided
Reference Count: 0
ISBN: ISBN-978-1-1095-7572-9
Analysis of Unbound Aggregate Layer Deformation Behavior from Full Scale Aircraft Gear Loading with Wander
Donovan, Phillip Raymond
ProQuest LLC, Ph.D. Dissertation, University of Illinois at Urbana-Champaign
This study focuses on the analysis of the behavior of unbound aggregates to offset wheel loads. Test data from full-scale aircraft gear loading conducted at the National Airport Pavement Test Facility (NAPTF) by the Federal Aviation Administration (FAA) are used to investigate the effects of wander (offset loads) on the deformation behavior of unbound aggregate layers in asphalt pavement test sections. The initial impetus for this study was the discovery that during a complete wander pattern some of the residual deformation caused by a single pass was recovered due to subsequent load applications offset by wander. The NAPTF applied a sequential wander pattern that covered 9 lanes of traffic spaced at 10.25 in. (260 mm) covering approximately 82% of all traffic from a standard normal distribution curve of real world taxiway traffic. Research into other full-scale airfield and highway tests indicates that this phenomenon is not unique to the NAPTF tests; this response to loading with wander has been recorded in full-scale tests since the early 1940's. This research has found that application of the wander pattern to the low and medium strength subgrade asphalt pavement test sections causes an "anti-shakedown" effect in the unbound aggregate layers. Essentially, study of multi-depth deflectometer data indicate that the unbound aggregate particles move because of the constantly changing load application lane. This movement negates the stabilization or shakedown expected in unbound aggregate layers under repeated loads and the strong stable particle matrix predicted to develop by shakedown theory never materializes. The second discovery in this work is that non-destructive falling or heavy weight deflectometer tests can be used to determine the relative damage in pavement foundations, i.e., unbound aggregate and subgrade layers. Two slope based deflection basin parameters, the Base Damage Index (BDI) and the Base Curvature Index (BCI) can be directly compared to determine the relative damage in the respective unbound aggregate and subgrade layers. Pinpointing the layer that is the likely cause of the system failure can help the pavement engineer correct the deficiency in the pavement system instead of only treating the symptoms. Discrete element modeling was also used to investigate the movement of unbound aggregate particles due to offset loads. The modeling indicates that the particles move from under the load application area to the sides, which in turn moves the particles initially to the side of the load application area upward because the particles moved from under the load area displace them. Wander or offset loads move the particles back under the initial load area causing particles in that area to move upward. The back and forth, upward and downward particle movement was readily apparent in the offset load application tests. Comparison of single load tests and multiple offset load tests indicates that particle movement is much greater when sequentially offset loads are applied. Comparison of channelized traffic and traffic with wander indicates that traffic with wander might be more detrimental to the unbound aggregate layers due to the increased movement and rearrangement of particles in the unbound aggregate layers. Measured transverse profiles and multi-depth deflectometer data were used to create individual pass residual deformation transverse profiles. The created transverse profiles were then combined with stress history effects to predict the residual transverse profiles for all test sections. This new permanent deformation model emphasizes the use of the previous load location and stress history of the pavement element to develop the residual deformation in that element. Calculation of the residual deformation in each element across the pavement surface results in the development of the complete permanent deformation transverse profile. This technique can be applied to estimate the transverse rutting profile of the pavement after trafficking based on any combination of applied wander and traffic direction. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page:]
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Publication Type: Dissertations/Theses - Doctoral Dissertations
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A