The contents do not necessarily reflect the official views or policies of the Illinois Center for Transportation, the Illinois Department of Transportation, or the Federal Highway Administration.
The contents of this report reflect the view of the authors, who are responsible for the facts and the accuracy of the data presented herein. for his help in providing data and performing field tests of this research. Douglas Steele from Applied Research Associates, Inc. Imad Al-Qadi and his students Wei Xie and Jongeun Baek for their help during Ground Penetrating Radar testing of Staley Road. Jamshid Ghaboussi for his invaluable contributions in this study. The coring method damages pavement, causes However, both these methods have limitations. Traditionally, two methods have been commonly used for in-situ asphalt mixture density measurement: laboratory testing on field-extracted cores and in-situ nuclear gauge testing. ii EXCUTIVE SUMMARY In-situ asphalt mixture density is critically important to the performance of flexible airport pavements: density that is too high, or too low, may cause early pavement distresses.
This paper does not constitute a standard, specification, or regulation. The research was conducted at the Advanced Transportation Research and Engineering Laboratory (ATREL) at the University of Illinois at Urbana-Champaign. The contents do not necessarily reflect the official views or policies of the CEAT or FAA. The contents of this study reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. The FAA project was conducted in cooperation with the Center of Excellence for Airport Technology (CEAT) and the University of Illinois at Urbana-Champaign. This report is based on the results of an FAA project, Nondestructive Testing and Evaluation (NDTE) Technologies for Airport Pavement Acceptance and Quality Assurance Activities. Keywords-Airfield pavements, ANN, backcalculation, new generation aircraft The changes in ANN-based backcalculated pavement moduli with trafficking were used to compare the relative severity effects of the aircraft landing gears on the NAPTF test pavements. The synthetic database generated using an advanced non-linear pavement finite-element program was used to train the ANN to overcome the limitations associated with conventional pavement moduli backcalculation. In this study, a multi-layer, feed-forward network which uses an error-backpropagation algorithm was trained to approximate the HWD backcalculation function. HWD tests were periodically conducted at the Federal Aviation Administration’s (FAA’s) National Airport Pavement Test Facility (NAPTF) to monitor the effect of Boeing 777 (B777) and Beoing 747 (B747) test gear trafficking on the structural condition of flexible pavement sections. The elastic moduli of the individual pavement layers backcalculated from the HWD deflection profiles are effective indicators of layer condition and are used for estimating the pavement remaining life. The HWD test is one of the most widely used tests for routinely assessing the structural integrity of airport pavements in a non-destructive manner. The study shows that, introducing frequency normalisation of both the pavement loading and vertical displacements to the backcalculation, can limit the statistical scatter of backcalculation results by close to a half in comparison with the classical backcalculation procedure.Abstract-This paper describes the use of artificial neural networks (ANN) for predicting non-linear layer moduli of flexible airfield pavements subjected to new generation aircraft (NGA) loading, based on the deflection profiles obtained from Heavy Weight Deflectometer (HWD) test data. This paper turns out that the seemingly small frequency of loading (≈20 Hz) generated during pavement deflection measurements using a Falling Weight Deflectometer-like device, has a significant impact on the backcalculation results of GM pavements. Despite a wide range of test results on the GM pavements presented in the literature, there are very few advanced modelling solutions formulated in the scope of bearing capacity measured in situ be means of a Falling Weight Deflectometer. This solution is known as Grouted Macadam (GM). Applying cement grout with a high compressive strength to a porous layer made of asphalt concrete results in a pavement with the properties of an intermediate type that combines the characteristics of both flexible and rigid pavements.