• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3D
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• pp.223-229
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• 2012

Skid resistance is defined as the friction between pavement surfaces and vehicle tires. Lower skid resistances were observed as the vehicle speeds the water film thicknesses were increased according to the analysis results using computer modeling. The lift force is calculated from the analysis results and depends on vehicle speeds and the water film thickness. A modified IFI(international friction index) skid resistance prediction model was developed to reduce the differences between the IFI resistance prediction model and the actual skid resistance. The correlation analysis results between the IFI prediction model and the actual skid resistance revealed that the $R^2$ using the modified IFI prediction model was 0.64 whereas the $R^2$ using the conventional IFI prediction model was 0.49. This presents the modified prediction model is better than the conventional one. An improved precise prediction model is to be obtained if water film thicknesses are considered in the modified prediction model.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.179-188
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• 2008

This study was performed as part of the development of the payment adjustment regulations for ensuring high performance of concrete pavements. The objectives of this study were to develop the reasonable quality measurement approaches for the implementation of the payment adjustment regulations and to propose the methods to determine the quality dependent pay factors. First, by using the statistics the slab thickness measurement data was analyzed and the methods to determine the allowable measurement errors, the proper measurement spacing, and the selection of the measurement location were proposed. In addition, to suggest the reasonable methods to determine the pay factors, by using the data of the slab thickness and concrete flexural strength, the pay factors based on the PWL(Percent Within Limits) method used in the USA were compared with those obtained considering the normal probability distribution and t distribution. Finally, the most appropriate method to determine the pay factors was proposed.

• International Journal of Highway Engineering
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• v.9 no.1 s.31
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• pp.57-67
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• 2007

Many researches have recently discussed about the film thickness as a good substitute or supplement for VMA or other volumetric criteria in the design procedure. Some researchers have not only proposed the specific number for the recommended film thickness, but also introduced the new calculation procedures or concepts. Each model (index model and the virtual model) has its own advantages and disadvantages in terms of the ability to account for the volumetric properties of the mixture. In this paper, the modified virtual model was proposed to combine advantages from both models. However, it cannot be disregarded the way to determine the appropriate particle shape factors for different sources and sizes of aggregates. In order to evaluate the different calculation methods, mixtures with two aggregate sources and eight gradations were designed based on the dominant aggregate size range (DASR) porosity concept. Superpave indirect tensile test (IDT) and asphalt pavement analyzer (AEA) test were used to describe the performance of mixtures. Test results indicated that the virtual model, which is the same to the modified virtual model for sphere 1:1 case, is better than the conventional standard model to define the range of the film thickness to have better performance of asphalt mixtures.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.23-33
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• 2017

Due to the rapid development of cities, densities and heights of urban structures are increased, and much larger and more underground spaces are being developed accordingly. Increasing development of underground spaces has induced more ground sinks and underground cavities. Therefore, safety of people is threatened by potential ground collapses and possible accidents, which may result from underground cavity. To actively respond against potential danger of ground sink, evaluation of existing cavity grade and development of recovery procedure are important. There exists the ground sinking management grade system of expressway developed as local standards in Japan. Recently, ground sinking management grade system of Seoul was developed with consideration of road and asphalt conditions. In this study, 209 underground cavities of ${\bigcirc}{\bigcirc}$ area were explored and their cavity shapes and grades were evaluated based on both ground sinking management grade systems of Japan and Seoul. Comparison is made between cavity grades evaluated based on both grading systems from Japan and Seoul. As a result of comparative analysis, the conservatively-estimated cavity grades requiring emergency restoration based on the Japanese management grade system of expressway result from neglection of layer thickness of surface pavement, considering only width and cover depth of a cavity.

• Journal of the Korean Geosynthetics Society
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• v.21 no.1
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• pp.49-56
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• 2022

In this study, finite element numerical analysis was performed considering various influence factors(cavity shape and size, pavement thickness and size of traffic load) in order to analyze the impact factors in the underground of the road where the cavity occurred and to evaluate the stability of the ground. In order to verify the reliability of the numerical analysis method applied in this study and the results it was compared and analyzed with the results of previous studies and field measurements. The correlation between the influence factors was analyzed through the distribution of vertical displacement obtained from the numerical analysis results, the distribution of surface settlement and surface settlement, the distribution of the stress ratio, and the distribution of the safety factor. As a result, it was confirmed that as the size of the cavity and traffic load increased and the thickness of the pavement decreased, the vertical displacement and surface settlement at the top of the cavity increased. Also, the shape of the cavity was square, the stability of the ground was significantly reduced compared to the case of a circular cavity. Through these results, it was possible to confirm the overall stability of the lower ground of the road where the cavity was generated.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.121-132
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• 2009

Thin bonded continuously reinforced concrete overlay(CRCO) was constructed on He existing jointed plain concrete pavement(HCP) surface at Seo-Hae-Ahn express highway in South Korea in order to evaluate its applicability and performance. Two sections of road were considered for this evaluation. In the first section, the concrete overlayer was placed and cut down to the existing layer to form transverse joints while CRCO was constructed on top of the existing layer in the second section. Early strength concrete(Type III) was utilized for both overlay sections. The depth of milling and the thickness of overlaid layer were 5 cm and 10 cm, respectively. Several vibrating wire gauges(VWG) were installed to evaluate the performance of CRCO with respect to curling, delamination, and crack propagation. As a result of the strength test, it was found that strength of the material reaches the design criteria within 1-3 days. Analysis with vibrating wire gauge(VWG) showed CRCO effectively restricts joint movement. High adhesive strength also was observed from the material regardless of length of aging. Meanwhile, transverse cracks were observed on the middle of the section where JPCP overlay was applied whereas arbitrarily cracks in transverse direction were observed on the section where CRCP was applied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.3
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• pp.285-294
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• 2020

This study investigated the use of Ground Penetrating Radar (GPR) over a two-decade period on public roads, focusing on the electromagnetic characteristics of the pavement dielectrics and attenuation. From the results, a typical range of characteristic value, influencing factors, and a correction method were suggested. The typical dielectrics of asphalt pavements were 4-7, as measured by an air-coupled 1 GHz GPR antenna. The dielectrics of concrete pavements were very large in the early age, but were drastically reduced with ageing. Ten years on, collection was in the range of 6-12. The dielectrics were proportional to the relative humidity (R.H.) of the atmosphere. The effects were reduced to one eighth with an overlay. Attenuation generally increased with thickness of the road layer, and also increased where there was damage. The GPR results could also vary depending on the weather conditions as well as on the characteristics of the GPR equipment, even at the same frequency. Therefore, GPR surveys should be performed on road surfaces without debris on a single, fine day. The reliability of the GPR analysis could be improved by cores and equipment calibration with other non-destructive test surveys.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.27-35
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• 2004

Most of concrete fatigue tests currently used are flexural tension or compression methods to investigate the tensile or compressive properties, respectively. However, the concrete pavement or concrete slab is actually subjected to a combined stress condition such as biaxial or triaxial. The split tension test may result in similar stress condition to biaxial stress condition. The purposes of this study were to evaluate the split tension fatigue test method for application in concrete. These were done by a finite element analysis and experimental series. The results were as follows: The optimum configuration of split tension fatigue test was a cylinder of 15cm in diameter and 7.5cm in thickness, which had a little different thickness compared to the KS standard cylinder of ${\phi}15{\times}30cm$. The concrete stress ratio of compressive against horizontal from FEA was 3.1, while that from theory was 3.0. The stress distributions of mortar and steel were almost similar at different thicknesses. The measured static split tensile strengths of concrete and mortar were quite similar at 30cm and 7.5cm thickness cylinders. The measured stress-strain relationship showed their consistency at all specimens regardless of thickness, and confirmed the results from FEA. As a results, the concrete split tension specimen, cylinder of 15cm in diameter and 7.5cm in thickness, could be used at fatigue test because of its accuracy, simplicity and convenience.

• International Journal of Highway Engineering
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• v.18 no.4
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• pp.55-61
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• 2016

PURPOSES : The objective of this study was to determine the relationship between the dielectric characteristics of asphalt mixtures and the air voids present in them using ground penetrating radar (GPR) testing. METHODS : To measure the dielectric properties of the asphalt mixtures, the reflection coefficient method and the approach based on the actual thickness of the asphalt layer were used. An air-couple-type GPR antenna with a center frequency of 1 GHz was used to measure the time for reflection from the asphalt/base layer interface. A piece of aluminum foil was placed at the interface to be able to determine the reflection time of the GPR signal with accuracy. An asphalt pavement testbed was constructed, and asphalt mixtures with different compaction numbers were tested. After the GPR tests, the asphalt samples were cored and their thicknesses and number of air voids were measured in the laboratory. RESULTS : It was found the dielectric constant of asphalt mixtures tends to decrease with an increase in the number of air voids. The dielectric constant values estimated from the reflection coefficient method exhibited a slight correlation to the number of air voids. However, the dielectric constant values measured using the approach based on the actual asphalt layer thickness were closely related to the asphalt mixture density. Based on these results, a regression equation to determine the number of air voids in asphalt mixtures using the GPR test method was proposed. CONCLUSIONS : It was concluded that the number of air voids in an asphalt mixture can be calculated based on the dielectric constant of the mixture as determined by GPR testing. It was also found that the number of air voids was exponentially related to the dielectric constant, with the coefficient of determination, $R^2$, being 0.74. These results suggest that the dielectric constant as determined by GPR testing can be used to improve the construction quality and maintenance of asphalt pavements.

• Geophysics and Geophysical Exploration
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• v.3 no.3
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• pp.94-100
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• 2000

Many nondestructive test methods used for metallic materials have some limit in application to concrete materials due to their heterogeneity. Impact echo method utilizes the resonance frequency of reflected seismic waves from defects or the boundary between two materials and can be applied to investigate the interior of concrete structures. In this study, a field data acquisition system for the impact echo method was assembled and field tests under various conditions were performed. The impact echo method was applied for investigating thickness/defects/backfilling of concrete structures/tunnel lining/airport pavement. The applicability of the impact echo method to the civil engineering field was substantiated by providing results within $10\%$ errors.