Comparison of Simplified Elastostatic and Elastodynamic Models for Falling Weight Deflectometer Data Interpretation

1996 ◽  
Vol 1540 (1) ◽  
pp. 72-76
Author(s):  
Dieter F. E. Stolle
Keyword(s):  
Structural Integrity ◽  
Data Interpretation ◽  
Falling Weight Deflectometer ◽  
System Parameters ◽  
Dynamic Impedance ◽  
In Situ Conditions ◽  
Subgrade Modulus ◽  
Falling Weight

The characterization of pavements and subgrades by interpreting falling weight deflectometer data is discussed. Two backcalculation strategies—one based on an approximate elastostatic model and the other on dynamic impedance for a two-layered pavement subgrade system—are presented and applied to data collected along experimental pavement sections. Both strategies characterize the structural integrity of a pavement by equivalent asphalt thickness and the stiffness of the subgrade by effective subgrade modulus. It is indicated that, although both procedures predict similar trends, the values of the system parameters differ, particularly the equivalent asphalt thickness. The net pavement-subgrade stiffness predicted using dynamic impedance was found to be consistently higher than that obtained with the elastostatic model for the data studied. The capability of dynamic impedance to identify variations of in situ conditions along a section of roadway is also demonstrated.

Influence of inertia on falling weight deflectometer (FWD) test response

1995 ◽  
Vol 32 (6) ◽  
pp. 1044-1048 ◽  
Author(s):  
Dieter F.E. Stolle ◽  
Gabriel Sedran
Keyword(s):  
Displacement Field ◽  
Load Distribution ◽  
Structural Integrity ◽  
Inertial Forces ◽  
Falling Weight Deflectometer ◽  
Ritz Vector ◽  
First Order ◽  
Back Calculation ◽  
Falling Weight

This note addresses the appropriateness of adopting an elastostatic model for backcalculating in situ layer moduli from falling weight deflectometer (FWD) data. By approximating the elastodynamic displacement field using an elastostatic solution for a given load distribution, it is shown via Ritz vector analyses that elastostatic fields do not accurately represent the displacements associated with pavements subjected to FWD-type loading. Some improvement is, however, possible by including first-order corrections for inertial forces. The main conclusion stemming from the analyses is that elastostatic models should not be used to estimate in situ moduli. Key words : pavement, elastodynamic analysis, Ritz vectors, back-calculation, structural integrity.

Falling weight deflectometer data interpretation using dynamic impedance

1996 ◽  
Vol 23 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Dieter Stolle ◽  
Farideddin Peiravian
Keyword(s):  
Data Interpretation ◽  
Angular Frequency ◽  
Elastic Half Space ◽  
Graphical Form ◽  
Falling Weight Deflectometer ◽  
Dynamic Impedance ◽  
Back Calculation ◽  
Actual Field ◽  
A Site ◽  
Falling Weight

This paper deals with the characterization of pavements and their supporting subgrade by comparing the measured dynamic impedance of a site, based on falling weight deflectometer data, with that of a two-layer, elastodynamic model. The pavement is modelled as a Kirchhoff plate and the subgrade as an incompressible, semi-infinite, elastic half space. The impedance of the two-layer problem is developed in graphical form as a function of a dimensionless angular frequency that depends on the pavement and subgrade properties. The characterization methodology outlined is applied to both simulated and actual field data. The effects of bedrock location and increasing subgrade stiffness with depth on dynamic impedance are addressed, and some limitations associated with the back calculation of system parameters are discussed. Key words: pavements, layer moduli, impedance, dynamic, back calculation.

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.

scholarly journals Application of FWD data in developing dynamic modulus master curves of in-service asphalt layers

2017 ◽  
Vol 23 (5) ◽  
pp. 661-671 ◽  
Author(s):  
Nader SOLATIFAR ◽  
Amir KAVUSSI ◽  
Mojtaba ABBASGHORBANI ◽  
Henrikas SIVILEVIČIUS
Keyword(s):  
Dynamic Modulus ◽  
Master Curve ◽  
Asphalt Pavements ◽  
Falling Weight Deflectometer ◽  
Master Curves ◽  
Simple Method ◽  
High Frequencies ◽  
Design Guide ◽  
Falling Weight

This paper presents a simple method to determine dynamic modulus master curve of asphalt layers by con­ducting Falling Weight Deflectometer (FWD) for use in mechanistic-empirical rehabilitation. Ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in Khuzestan and Kerman provinces in south of Iran. FWD testing was conducted on these pavements and core samples were taken. Witczak prediction model was used to predict dynamic modulus master curves from mix volumetric properties as well as the bitumen viscosity characteristics. Adjustments were made using FWD results and the in-situ dynamic modulus master curves were ob­tained. In order to evaluate the efficiency of the proposed method, the results were compared with those obtained by us­ing the developed procedure of the state-of-the-practice, Mechanistic-Empirical Pavement Design Guide (MEPDG). Re­sults showed the proposed method has several advantages over MEPDG including: (1) simplicity in directly constructing in-situ dynamic modulus master curve; (2) developing in-situ master curve in the same trend with the main predicted one; (3) covering the large differences between in-situ and predicted master curve in high frequencies; and (4) the value obtained for the in-situ dynamic modulus is the same as the value measured by the FWD for a corresponding frequency.

scholarly journals Assessment Of Designed And Measured Mechanistic Parameters Of Concrete Pavement Foundation

2019 ◽  
Vol 14 (1) ◽  
pp. 37-57
Author(s):  
Yang Zhang ◽  
Pavana Vennapusa ◽  
David Joshua White
Keyword(s):  
California Bearing Ratio ◽  
Cone Penetrometer ◽  
Falling Weight Deflectometer ◽  
In Situ Tests ◽  
Target Value ◽  
Dynamic Cone Penetrometer ◽  
Support Conditions ◽  
Falling Weight ◽  
Pavement Foundation

There are plenty of in situ tests available to examine pavement foundation performance regarding stiffness and support conditions. This study evaluates several in situ tests of the stiffness and support conditions of concrete pavement foundation layers. The principal objective of this study was to evaluate the outputs from Dynamic Cone Penetrometer tests and Falling Weight Deflectometer tests. The California Bearing Ratio from Dynamic Cone Penetrometer tests and the deflection data from Falling Weight Deflectometer tests were correlated to the design parameter – modulus of subgrade reaction k through correlations employed in pavement design manuals. Three methods for obtaining the k values were conducted, with the intent to evaluate which method provides the results most similar to the target value and whether the studied correlations are reliable. The back-calculated k values from Falling Weight Deflectometer deflections and the weak layer California Bearing Ratio correlated k values based on the Portland Cement Association method were close to the target value, while the California Bearing Ratio empirically correlated k based on the American Association of State Highway and Transportation Officials method presented values significantly higher than the target value. Those previously reported correlations were likely to overestimate the k values based on subgrade California Bearing Ratio values.

Synchrotron X-ray tomographic characterization of microstructural evolution in coal due to supercritical CO2 injection at in-situ conditions

Fuel ◽  
2019 ◽  
Vol 255 ◽  
pp. 115696 ◽  
Author(s):  
Guanglei Zhang ◽  
P.G. Ranjith ◽  
Bisheng Wu ◽  
M.S.A. Perera ◽  
Asadul Haque ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Supercritical Co2 ◽  
Co2 Injection ◽  
X Ray ◽  
In Situ Conditions ◽  
Supercritical Co2 Injection

A practical approach to falling-weight deflectometer (FWD) data reduction

2005 ◽  
Vol 42 (2) ◽  
pp. 641-645 ◽  
Author(s):  
Dieter Stolle ◽  
Peijun Guo
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Falling Weight Deflectometer ◽  
Layer System ◽  
Surface Loading ◽  
Back Calculation ◽  
Pavement Response ◽  
Subgrade Modulus ◽  
Falling Weight

The authors present a simplified methodology for preprocessing falling-weight deflectometer (FWD) data, which identify a pseudo-static pavement response to surface loading. This allows one to employ static analysis to back-calculate the mechanical properties of the pavement–subgrade system. It is shown that the subgrade modulus can be identified, independent of the details of the pavement structure itself, at least for a two-layer system. The quality of the effective shear modulus is sensitive to the value of Poisson's ratio selected.Key words: pavement–subgrade system, subgrade modulus, back-calculation, FWD.

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