• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.261-271
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• 2003

A condition evaluation procedure for the pavement foundations using multi-load level Falling Weight Deflectometer(FWD) deflections is presented in this paper. A dynamic finite element program incorporating a stress-dependent material model, was used to generate the synthetic deflection database. Based on this synthetic database, the relationships between surface deflections and critical responses, such as stresses and strains in base and subgrade layers, have been established. FWD deflection data, Dynamic Cone Penetrometer(UP) data, and repeated load resilient modulus testing results used in developing this procedure were collected from the Long Term Pavement Performance (LTPP) and North Carolina Department of Transportation (NCDOT) database. Research effort focused on investigation of the effect of the FWD load level on the condition evaluation procedures. The results indicate that the proposed procedure can estimate the pavement foundation conditions. It is also found that structurally adjusted Base Damage Index (BDI) and Base Curvature Index (BCI) are good indicators for the prediction of stiffness characteristics of aggregate base and subgrade respectively. A FWD test with a load of 66.7 kN or less does not improve the accuracy of this procedure. Results from the study for the nonlinear behavior of a pavement foundations indicate that the deflection ratio obtained from multi-load level deflections can predict the type and quality of the pavement foundation materials.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.31-35
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• 2006

Cement stabilisation is a common method for stabilising recycled road base material and provides a longer pavement life. With cement effect, the increment of stiffness in the stabilised layer would provide better load transfer to the pavement foundation. The recycling method provides an environmentally option as the existing road base materials will not be removed. This paper presents a case study of a trial section along the North-South Expressway in West Malaysia, where the Falling Weight Deflectometer (FWD) was implemented to evaluate the compressive strength and in-situ stiffness of the cement stabilised road base material. The improvement in stiffness of the cement stabilised base layer was monitored, and samples were tested during the trial. FWD was found to be useful for the structural assessment of the cement-stabilised base layer prior to placement of asphalt layers. Results from the FWD were applied to verify the assumed design parameters for the pavement. Using the FWD, an empirical correlation between the deflection and the stiffness modulus of the pavement foundation is proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.203-214
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• 2024

Ports often suffer pavement damage due to soft ground and heavy equipment operations, leading to issues such as differential settlement and cracks. In this study, we developed port concrete blocks and applied them to a port in two configurations to figure out settlement characteristics. Falling weight deflectometer (FWD) tests on asphalt pavement and block pavements were conducted to figure out deflection and bearing capacity. The block pavement with the cement treated base showed improved bearing capacity with the port operation since lower settlements were detected than asphalt pavement. In the cement treated base, the relative deflection ratio to asphalt concrete pavement was less than 1, indicating enhanced bearing capacity. LiDAR measurements identified multiple settlements in the crushed-stone base due to surface loads after construction. Both relative deflection ratio and LiDAR measurements suggested that block pavement can be widely applied to various port sites with its applicability and bearing capacity of cement-treated base.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.797-804
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• 2006

A development of regression model for asphalt concrete pavements using Falling Weight Deflectometer deflections is presented in this paper. A backcalculation program based on layered elastic theory was used to generate the synthetic modulus database, which was used to generate 95% confidence intervals of modulus in each layer. Using deflection basins of FWD data used in developing this procedure were collected from Pavement Management System in flexible pavements. Assumptions of back-calculation are that one is 3 layered flexible pavement structure and another is depth to bedrock is finite. It is found that difference of between 95% confidence intervals and modulus ranges of other papers does not exist. So, the data of 95% confidence intervals in each layer was used to develop multiple regression models. Multiple regression equations of each layer were established by SPSS, package of Statics analysis. These models were proved by regression diagnostics, which include case analysis, multi-collinearity analysis, influence diagnostics and analysis of variance. And these models have higher degree of coefficient of determination than 0.75. So this models were applied to predict modulus of domestic asphalt concrete pavement at FWD field test.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.781-786
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• 1999

One of the major causes of concrete pavement deterioration is the loss of support due to erosion and pumping of subbase and subgrade. In this study, procedures for the detection of voids under concrete pavement slab are presented using nondestructive test method such as FWD(Falling Weight Deflectometer) and GPR(Ground Penetration Radar). The deflection responses of concrete slab obtained in FWD field test are analysed for determining the presence of void. Also, reflection responses in GPR test are interpreted. It was concluded that these procedures are available for detecting the viods under concrete pavement slab.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.69-78
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• 2014

PURPOSES : The purpose of this paper is showing that the state of pavement sublayers can be evaluated differently according to direction of FWD. METHODS : The concrete pavement slabs above subgrade without anything, subgrade with cavity, and box culvert were modeled by finite element method(FEM). The modeled pavements were analyzed by changing the direction of falling weight deflectometer(FWD). The deflection results obtained from FEM were used to calculate radius of relative stiffness and composite modulus of subgrade reaction using AREA method. Then, the analyzed results were compared to the results of the test performed at the Korea Expressway Corporation(KEC) test road. RESULTS : The composite modulus of subgrade reaction increased with subgrade elastic modulus, while radius of relative stiffness decreased. The pavement sections of pure earth showed the consistent results regardless of FWD direction. In case there was cavity, the radius of relative stiffness was larger and composite modulus of subgrade reaction was smaller when FWD was leaving the cavity than when approaching the cavity. This pattern became clear when the cavity got larger. In case of the section with box culvert, the pattern was opposite to the case of cavity. When the soil cover depth increased, the effect of box culvert got smaller. When the load was applied far from the cavity and box culvert, the effect was also declined. The test performed at the KEC test road showed identical results to those of finite element analysis. CONCLUSIONS : The direction of FWD should be considered in evaluation of the state of pavement sublayers because it can be evaluated differently even under identical condition.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.99-106
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• 2010

Until now, the thickness design of anti-freezing layer has been empirically conducted using the frost depth determined from the freezing index. This approach cannot consider the structural properties of anti-freezing layer, which can cause the over-design of pavement structure. This paper presents results of structural evaluation of anti-freezing layer using the Falling Weight Deflectormeter (FWD) deflections. The FWD testing was directly conducted on top of the subbase layer located at the embankment, cutting, and boundary area of each section. It is observed from this testing that the center deflections of pavement structure with anti-freezing layer are smaller than those without anti-freezing layer. The deflection reduction rates are 15~55% in the embankment, 11~64% in the cutting, and 2~38% in the boundary, respectively. It was also found that the use of antifree zing layer enables to reduce the Surface Curvature Index (SCI) values up to 24 percent. Fatigue lives show that pavement structure with antifreezing layer are about two times higher than the those without anti-freezing layer. This fact indicates that the anti-freezing layer should be considered as a structural layer in the asphalt pavement system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.1
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• pp.97-107
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• 1989

An inverse self-iterative procedure is developed to estimate layer moduli of 3 layered flexible pavement structures from FWD deflection basins. The theoretical deflection basins of pavement structures obtained by full factorial design are used for the parametric study on the characteristics of deflection basins and the regression analysis. The factorial design is performed for asphalt pavement structures with stabilized base layer and granular base layer, respectively. The initially assumed layer moduli by regression equations and relations between the rate of change of moduli and deflections are used in the procedure to ensure efficiency and accuracy of self-iterative model. The SINELA computer program is used for inverse self-iterative applications to determine theoretical responses. The computer program of this procedure is coded for personal computers and is verified through numerical model tests.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.5
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• pp.89-96
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• 2012

The Falling Weight Deflectormeter has been widely used in evaluating the structural adequacy of pavement structures. The deflections measured from the FWD are capable of estimating the stiffness of pavement layers and measuring the pavement responses in the pavement structure. The objective of paper is to develop the pavement response model using a partial least square regression technique based on the FWD deflection data. The partial least square regression method enables to solve the multicollinearity problem occurred in multiple regression model. It is also found that the pavement response model can be developed using the raw data when a partial least square regression was used.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.25-32
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• 2012

The thickness of anti-freezing layer has been empirically determined using the frost depth obtained from the freezing index and has not been generally considered as a structural layer in pavement design procedure. In fact, the anti-freezing layer makes a role in structural layer and enables to reduce the total thickness of pavement system. The objective of this study is to develop the statistical regression model for evaluating the structural capacity of anti-freezing layer using Falling Weight Deflectormeter(FWD) test data in asphalt pavements. The FWD testing was conducted at the embankment, cutting, and boundary area of various test sections to estimate the structural capacity of anti-freezing layer in different foundation condition. It is observed from this testing that the center deflections of pavement structure with anti-freezing layer are smaller than those without anti-freezing layer ranging from 0.4 to 82.6%. To determine the variables of statistical model, the correlation study has been conducted between various FWD deflection indexes and the anti-freezing layer thickness. It is found that the ${\Delta}BDI$(%)(${\Delta}Basin$ Damage Index(%)) is highly correlated with anti-freezing layer thickness. The ${\Delta}BDI$(%) model were developed for evaluating structural capacity of anti-freezing layer using linear mixed-effect models.