Nondestructive Testing: Interpretation of Deflection Bowl for Falling Weight Deflectometer Tests on Flexible Pavements

1989 ◽  
Vol 17 (6) ◽  
pp. 333
Author(s):  
A Wolfenden ◽  
FW Jung
Keyword(s):  
Nondestructive Testing ◽  
Flexible Pavements ◽  
Falling Weight Deflectometer ◽  
Falling Weight

Direct Method for Evaluating Structural Needs of Flexible Pavements with Falling-Weight Deflectometer Deflections

2003 ◽  
Vol 1860 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Mario S. Hoffman
Keyword(s):  
Direct Method ◽  
Flexible Pavements ◽  
Falling Weight Deflectometer ◽  
Simple Method ◽  
Traffic Demand ◽  
Structural Evaluation ◽  
Overlay Design ◽  
Subgrade Modulus ◽  
Simple Equations ◽  
Falling Weight

A direct and simple method (YONAPAVE) for evaluating the structural needs of flexible pavements is presented. It is based on interpretation of measured falling-weight deflectometer (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 the determination of the overlay required to accommodate future needs. YONAPAVE’s 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 independence from major computer programs, make YONAPAVE suitable for estimating the structural needs of a road network using FWD data collected on a routine or periodic basis along network roads. YONAPAVE can be used with increased experience and confidence as the basis for nondestructive testing structural evaluation and overlay design at the project level.

Dynamic Interpretation for Impulsive Deflection Test on Flexible Pavements

1998 ◽  
Vol 14 (2) ◽  
pp. 91-100
Author(s):  
Der-Wen Chang ◽  
Chia-Ling Chang
Keyword(s):  
Iterative Scheme ◽  
Flexible Pavements ◽  
Falling Weight Deflectometer ◽  
Correction Procedure ◽  
Subgrade Soils ◽  
Forward Analysis ◽  
Dynamic Interpretation ◽  
Equivalent Number ◽  
Deflection Test ◽  
Falling Weight

AbstractIn this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflectometer (FWD) test on flexible pavements. To backcalculate the layer moduli of the pavement, a number of iterative backcalculation schemes were employed with the forward analysis of the Green's flexibility influence functions. The temperature and the moisture influences on material moduli of the asphalt surface and the subgrade soils were considered in the analysis. As the result, the iterative scheme based on the peak deflection ratios was selected to backcalculate the layer moduli of local pavements. Owing to the correction procedure used in the program, interpretations with four original deflections were found more accurate than those with equivalent number of modified deflections. Comparisons of program DBFWD with other static backcalculation programs on theoretical and experimental deflections indicated that dynamic interpretation is more effective in providing the layer modulus information. Despite of the requirements of accurate inputs of the layer thickness and the testing load for the analysis, a generalized application of the program needs to be clarified with model road test in demand.

Field Assessment of Changes in Pavement Moduli Caused by Freezing and Thawing

1998 ◽  
Vol 1615 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Da-Tong Jong ◽  
Peter J. Bosscher ◽  
Craig H. Benson
Keyword(s):  
Flexible Pavements ◽  
Complete Recovery ◽  
Meteorological Conditions ◽  
Phase Changes ◽  
Water Phase ◽  
Falling Weight Deflectometer ◽  
Freezing And Thawing ◽  
Field Assessment ◽  
Falling Weight ◽  
Water Contents

Three secondary highways with flexible pavements were instrumented for 18 months to monitor changes in pavement moduli caused by seasonal meteorological changes. Temperatures, water contents, and water phase changes in the subsurface as well as meteorological conditions were recorded every 2 hours throughout the study. Pavement moduli were regularly determined by conducting surveys with a falling weight deflectometer and by performing backcalculations using the program Modulus. The moduli of the base and subgrade typically increased 12 to 4 times, respectively, when frost penetrated the subsurface. When the base and subgrade began to thaw, the moduli decreased substantially. The base moduli decreased the most, typically being about 35 percent of the prefreezing values by the end of thaw. Smaller decreases occurred in the subgrade. The subgrade moduli were about 65 percent of their prefreezing values by the end of thaw. The moduli continued to decrease until thaw was complete and then gradually recovered back to the original prefreezing values. Complete recovery required approximately 4 months. Similar changes in moduli were observed regardless of site or year.

Prediction of Remaining Life of Asphalt Pavement with Falling-Weight Deflectometer Multiload-Level Deflections

2003 ◽  
Vol 1860 (1) ◽  
pp. 48-56 ◽  
Author(s):  
Hee Mun Park ◽  
Y. Richard Kim
Keyword(s):  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Pavement Performance ◽  
Falling Weight Deflectometer ◽  
Remaining Life ◽  
Performance Models ◽  
Response Models ◽  
Wide Range ◽  
Pavement Response ◽  
Falling Weight

The development of prediction methods for the remaining life of flexible pavements using falling-weight deflectometer (FWD) multiload-level deflections is presented. Pavement response models and pavement performance models were used in developing this procedure. The pavement response models were designed to predict critical pavement responses from surface deflections and deflection basin parameters. The pavement performance models were used to develop the relationships between critical pavement responses obtained from pavement response models and actual pavement performance. Pavement distress data and FWD multiload-level deflection data obtained from the Long-Term Pavement Performance database were used to verify the performance prediction procedure. It was found that the performance of fatigue cracking can be predicted using the proposed procedure except for pavements with high and rapidly increasing cracking in wet-freeze regions. Such trends may be due to environment-induced distresses such as low-temperature cracking, permanent deformation of unbound layers, or both, during the spring thaw period. Predicted rut depths using both single-load and multiload-level deflections show good agreement with measured rut depths over a wide range of rutting potentials. However, the procedure using single–load-level deflections consistently underpredicts the rut depths. This observation demonstrates that the rutting prediction procedure using multiload-level deflections can estimate an excessive level of rutting quite well and thus improve the prediction quality of rutting potential in flexible pavements.

Use of Locally Available Soils on Subbase and Base Layers of Flexible Pavements

2003 ◽  
Vol 1819 (1) ◽  
pp. 110-121 ◽  
Author(s):  
Lilian Ribeiro de Rezende ◽  
José Camapum de Carvalho
Keyword(s):  
Flexible Pavements ◽  
Federal District ◽  
Lateritic Soil ◽  
Crushed Rock ◽  
Falling Weight Deflectometer ◽  
In Situ Tests ◽  
Strain Behavior ◽  
Low Volume Roads ◽  
Falling Weight

Lateritic soils are very abundant in the region of the Federal District of Brazil. If this material could be used in low-volume roads, it would be possible to avoid some environmental problems. Alternative techniques were developed for the use of nonconventional materials as subbase and base layers of flexible pavements. To analyze the technical and economical viability of using local soils, two experimental highways were constructed. Each highway was divided into three sections with different materials in the subbase and base layers, such as fine lateritic soil, fine lateritic soil stabilized with lime, and a mixture of fine lateritic soil and crushed rock. The compaction characteristics were evaluated in laboratory tests. From the time the segments were constructed (in 1998 and 2000) until 2001, the stress–strain behavior of the paving structures was evaluated by in situ tests, such as the plate-bearing, Benkelman beam, and falling weight deflectometer tests. From the results, conclusions were drawn about which of the chosen materials showed the best performance in mechanical behavior.

Dynamic Viscoelastic Analysis of Falling Weight Deflectometer Deflections for Rigid and Flexible Pavements

2015 ◽  
Vol 2525 (1) ◽  
pp. 31-39 ◽  
Author(s):  
Lev Khazanovich ◽  
Abbas Booshehrian
Keyword(s):  
Flexible Pavements ◽  
Viscoelastic Plate ◽  
Hankel Transform ◽  
Winkler Foundation ◽  
Falling Weight Deflectometer ◽  
Response Data ◽  
Proposed Model ◽  
Viscoelastic Effects ◽  
Falling Weight ◽  
Measured Response

This paper investigates the ability of a generalized Westergaard model consisting of a viscoelastic plate on a viscoelastic Winkler foundation to describe deflections of both rigid and flexible pavements under dynamic loading. The pavement response to falling weight deflectometer (FWD) loading was simulated, and a semianalytical solution involving the use of a Hankel transform in space and a finite difference method in time was developed. The obtained solution was used to interpret FWD data collected at the Minnesota Road Research Facility. It was shown that a good match between the simulated and measured response data could be obtained for both rigid and flexible pavements if inertia and viscoelastic effects were accounted for. The proposed model is thus an attractive tool for analysis of pavement–vehicle interaction.

Feasibility of Backcalculation of Nonlinear Flexible Pavement Layer Parameters from Nondestructive Testing

2003 ◽  
Vol 1860 (1) ◽  
pp. 16-25 ◽  
Author(s):  
Amitis Meshkani ◽  
Imad N. Abdallah ◽  
Soheil Nazarian
Keyword(s):  
Nondestructive Testing ◽  
Laboratory Testing ◽  
Nonlinear Behavior ◽  
Falling Weight Deflectometer ◽  
Nonlinear Parameters ◽  
Pavement Materials ◽  
Linear Elastic ◽  
Texas Department ◽  
Pavement Structures ◽  
Falling Weight

Nondestructive testing (NDT) methods are typically used to measure the variations in the modulus of different pavement layers. The falling-weight deflectometer (FWD) and the seismic pavement analyzer (SPA) are two of the NDT devices used for this purpose by the Texas Department of Transportation. Since the loads applied by the FWD to the pavement are similar to those exerted by traffic, the FWD moduli are used in pavement design and analysis without adjusting them for the nonlinear behavior of the materials. Seismic moduli are similar to linear elastic moduli since they correspond to small external loads. A constitutive model that considers nonlinear behavior of pavement materials is essential in order to convert seismic moduli to those appropriate for the state of stress applied by a truck. Nonlinear parameters needed for these models can normally be obtained from laboratory testing. A study was carried out to determine whether these nonlinear parameters can be estimated from the FWD deflection basin alone or from integration of the seismic and FWD data. FWD deflection alone in most cases does not seem to contain enough information to reliably provide the nonlinear parameters of the layers. Combining the seismic and deflection data would allow the estimation of some of the nonlinear parameters for weaker pavement structures. In the authors’ experience, the most reliable way to estimate the nonlinear parameters of base and subgrade is still laboratory testing.

Dynamic interpretation of falling weight deflectometer tests on flexible pavements using the spectral element method: backcalculation

2009 ◽  
Vol 36 (6) ◽  
pp. 957-968 ◽  
Author(s):  
Simon Grenier ◽  
Jean-Marie Konrad
Keyword(s):  
Spectral Element Method ◽  
Flexible Pavements ◽  
Spectral Element ◽  
Falling Weight Deflectometer ◽  
Dynamic Approach ◽  
Dynamic Interpretation ◽  
Minimization Technique ◽  
The Time Domain ◽  
Falling Weight ◽  
Element Method

A robust backcalculation methodology that uses the Levenberg–Marquardt iterative minimization technique is presented to identify the value of unknown layer parameters from falling weight deflectometer (FWD) tests using a dynamic approach based on the spectral element method. Backcalculation is performed in the time-domain with 20 observations on each deflection history. The efficiency of the proposed methodology is demonstrated by interpreting FWD tests on three flexible pavements that cover a variety of structures, soil, and bedrock conditions. Results indicate that the dynamic approach is capable of simulating quite well the measured deflection histories using effective backcalculated moduli. In addition, comparison of critical strains between static and dynamic interpretation of FWD tests indicates that both approaches predict similar traction strains at the bottom of the asphalt concrete layer. However, the prediction of the compression strain in the subgrade with the static approach is erratic compared with the dynamic method.

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