Benchmarking the structural condition of flexible pavements with deflection bowl parameters (original) (raw)
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FALLING WEIGHT DEFLECTOMETER BOWL PARAMETERS AS ANALYSIS TOOL FOR PAVEMENT STRUCTURAL EVALUATIONS
The falling weight deflectometer (FWD) is used world wide as a well established and valuable non-destructive road testing device for pavement structural analyses. The FWD is used mostly for rehabilitation design investigations and for pavement management system (PMS) monitoring on a network basis. On project level investigations, both design charts and mechanistic approaches using multi-layered linear elastic theory and back-calculation procedures are often used to provide structural evaluations and rehabilitation options. As an alternative to this a semi-mechanistic semi-empirical analysis technique has been developed in South Africa whereby new deflection bowl parameters measured with the FWD used to give guidance on individual layer strengths and pinpoint rehabilitation needs. This approach is fully suited to supplementary analysis of FWD data in the Australian design systems, and overcomes some of the limitations of the curvature parameter. This paper briefly describes the current practice and basis of this use of deflection bowl parameters, and illustrates the use with a current pavement rehabilitation project underway in South Africa.
A benchmark analysis methodology utilising the imbedded structural response knowledge of the whole deflection bowl measured with the Falling Weight Deflectometer (FWD) was developed for comparative evaluation of the structural condition of flexible pavement structures. Zones in the pavement structure are associated with structural condition via correlations with various slope parameters on the measured deflection bowl determined from simple spreadsheet calculations. Deflection bowl parameter benchmarking has found application at network level analysis with FWD data by a number of road authorities world-wide. A number of additional area parameters based on various areas under the deflection bowl have recently been added, These additional deflection bowl parameters were evaluated and found to strengthen the established pavement benchmark structural analyses as a preliminary evaluation tool. More recently it was illustrated that structural condition indices such as the internationally ...
Transportation Research Record, 2003
A direct and simple method (YONAPAVE) for evaluating the structural needs of flexible pavements is presented. It is based on the interpretation of measured FWD deflection basins using mechanistic and practical approaches. YONAPAVE estimates the effective Structural Number (SN) and the equivalent subgrade modulus independently of the pavement or layer thicknesses. Thus, there is no need to perform boreholes which are expensive, time consuming and disruptive to traffic. Knowledge of the effective SN and the subgrade modulus, together with an estimate of the traffic demand, allows for the determination of the overlay required to accommodate future needs. YONAPAVE simple equations can be solved using a pocket calculator, making it suitable for rapid estimates in the field. The simplicity of the method, and its independency of major computer programs, makes YONAPAVE suitable for estimating the structural needs of a road network using FWD data collected on a routine or periodic basis along the network roads. With increasing experience and confidence, YONAPAVE can be used as the basis for NDT structural evaluation and overlay design at the project level.
A benchmark analysis method was developed using Falling Weight Deflectometer (FWD) data for comparative evaluation of the structural condition of flexible pavement structures. This is established as a preliminary design and analysis tool, and aspects of it are incorporated in TRH 12. Experiences with benchmark analyses on roads and airports are reviewed and adjusted criteria are recommended with a colour coded three tiered condition assessment method. Exploratory studies on additional deflection bowl parameters are conducted to gauge their potential for inclusion in benchmark analyses. Deflection bowl parameter benchmarking has found application at network level analysis in a number of road authorities world-wide. Modified Structural Number (SNP) and Pavement Number (PN) have recently also been illustrated as being able to accurately calculate from the full deflection bowl and can be used in such enhanced benchmark analyses of flexible pavement structures.
REVIEW OF FALLING WEIGHT DEFLECTOMETER FOR ASSESSMENT OF FLEXIBLE PAVEMENT
ELK ASIA PACIFIC JOURNAL OF CIVIL ENGINEERING AND STRUCTURAL DEVELOPMENT , 2018
Fast development of road networks has become a trend in India and everywhere in the world. From the past couple of decades, it has been observed that numerous highways are in a phase of deteriorations. Identifying the reasons for deteriorations requires a pavement evaluation study. Many performances study have been made out by exploring flexible pavements, by the users of widely accepted falling weight deflectometer (FWD) as a non-destructive test (NDT) and considered it as a standard for structure assessment. The primary objective of this study is to a review of an FWD instrument and the also study of the empirically derived methods and a back calculation process for computing layer moduli and factors influencing it. The essential need of correction factors to get reliable layer moduli is an also discussed, in addition to the investigation of advancement of low-cost indigenous FWD models flexible pavements, by the users of widely accepted falling weight deflectometer (FWD) as a non-destructive test (NDT) and considered it as a standard for structure assessment. The primary objective of this study is to a review of an FWD instrument and the also study of the empirically derived methods and a back calculation process for computing layer moduli and factors influencing it. The essential need of correction factors to get reliable layer moduli is an also discussed, in addition to the investigation of advancement of low-cost indigenous FWD models
2017
This report documents a study conducted to review the status of falling weight deflectometer (FWD) equipment, data collection, analysis, and interpretation, including dynamic backcalculation, and to develop enhanced analysis procedures and recommendations for the effective use of FWD technology as it relates to the flexible pavement models and procedures incorporated within the Mechanistic-Empirical Pavement Design Guide developed by the National Cooperative Highway Research Program and subsequently adopted by the American Association of State Highway and Transportation Officials. In this context, dynamic backcalculation refers to the modeling of the dynamic or impact nature of the FWD loading and resulting pavement response of in-service flexible pavements for pavement structural analysis and rehabilitation design. The research effort resulted in development analysis methodologies, software tools implementing those analysis methodologies and a potential list of recommendations for FWD equipment enhancements, all of which are detailed in this report. This report is intended for use by pavement engineers involved in structural evaluation and rehabilitation design of flexible pavements and researchers involved in development of new procedures for the modeling and analysis of in-service flexible pavements.
2012
The paper describes a procedure where the condition of flexible pavements is investigated with the help of non-destructive tests such as the Falling Weight Deflectometer (FWD). The condition or indication of structural strength is expressed in terms of the Structural Number (SN). An existing method of determining the Structural Number was used as benchmark with data from a recent detailed pavement investigation. The benchmark SN determination also makes use of the Dynamic Cone Penetrometer (DCP) method. Previously only limited aspects of the measured deflection bowl were used to determine SN non-destructively. In this improved procedure additional deflection bowl parameters were investigated for their possible improvement in the determination of the SN or PN. The proposed method was therefore benchmarked against existing methods to determine SN for a pavement to see if it can lead to an improvement in determining SN values.
FLEXIBLE PAVEMENTS – STRUCTURAL EVALUATION BASED ON DEFLECTION BASIN PARAMETERS
LOPES Flaviane Melo; FORTES Rita Moura; SUZUKI Carlos Yukio.. Flexible pavements – structural evaluation based on deflection basin parameters, 2013 IJPC – International Journal of Pavements Conference. São Paulo, Brazil, December 9-10, 2013. Abstract: In Brazil it is significant the increase in the use of an equipment type FWD for deflection analysis and structural characterization of existing pavements. This characterization is still held only through a maximum deflection measure. However, the isolated association of maximum deflection (D0) may not be conclusive enough to diagnose the structural condition of the pavement. Thus, the current study aims, through parametric study, to propose a simplified structural assessment methodology of asphalt pavement condition with granular base using measurements of deflection basin. Through the known correlations simplified models will be proposed to estimate the remaining life of a pavement according to deflection parameters. The proposed methodology has proved to be promising. The use of the information on deflection basin can help out in troubleshooting pavement rehabilitation, avoiding premature failures in diagnosing faults.
Application of deflection bowl parameters for assessing different structures of road pavement
MATEC Web of Conferences, 2018
To date, non-destruction testing (NDT) method is the most popular method to assess the condition of road pavement. Among all evaluation procedures of the NDT method, load-deflection backcalculation analysis is one that is developed widely to understand the structural behavior of road pavement. On one side, the use of this analysis is greatly beneficial for presenting the layer characteristic accurately. However, the analysis requires specialist expertise. To overcome this, deflection bowl parameter application could become one alternative. The parameters are very easy to use; however, the intention of the parameters so far is only as an indication of the condition of the structural layer of the road pavement. Therefore, the parameters have to be used with careful consideration. In this study, the parameters were evaluated to determine the optimal usage of the parameters against different structures of road pavements. The results showed that a simplification of the number of paramete...