Recently, in Seoul, Korea, GPR (Ground Penetration Rader)-based road cavities exploration technology was introduced for the exact cause analysis of road subsidence. The city of Seoul has identified a total of 2504 cavity in 2017 by using the introduced road cavities exploration technology, which shows that the incidence rate of road subsidence is reduced by 67%. However, GPR-based exploration technology is mainly concerned with cavities in the underground of the road pavement, and there is no effective method for areas with a danger zone depth of 1.5m or more and special areas such as narrow sidewalk. The EM (Electro Magnetic) method can be used to check the existence of cavities and poor ground in the underground using information on the location, shape, and electrical conductivity of the anomaly zone in the underground by measuring the electromagnetic field. Therefore, in this study, want to predict with a danger zone area by exploring the underground in the narrow sidewalk or park road by using the EM equipment which is capable of deep geological exploration, non - contact and equipment size change. In the previous research, the underground exploration was performed by simulating the ground and the cavities and the cavities including the metal. As a result, it was confirmed that an electrical resistivity anomaly zone occurred in the cavity regardless of the existence of the metal. Therefore, in order to analysis the applicability of the EM method in the underground cavities area according to the field simulation, this study will conduct the outside experiment by simulating actual sidewalk or asphalt pavement. In the future, the researchers will plan to examine the applicability of various factors such as type, condition and depth of road pavement.

Airport concrete pavement slabs show contraction and expansion behavior due to environmental factors such as temperature and humidity. Among the various environmental factors, temperature is the most influential factor in the concrete slab. However, it is inadequate to consider air temperature or surface temperature as influential factors especially for airport concrete slabs with very large thicknesses. Therefore, this study intends to utilize the equivalent linear temperature difference calculated from the data of the thermometer embedded in 5 depths(50mm, 150mm, 250mm, 350mm, 450mm) on the airport concrete slab. Equivalent linear temperature difference is the temperature difference between the uppermost and lowermost part of the concrete slab, which shows the same behavior due to actual temperature. Since the upper part of the concrete slab is more affected by air temperature than the lower part, the daily temperature range is large. Therefore, the equivalent linear temperature difference increases during the day and decreases at night, and concrete slabs show curl-down during the day and curl-up at night. This daily variation of curling behavior causes a difference in HWD experimental results. The HWD(Heavy Weight Deflectometer) test is mainly performed to investigate the condition of the pavement. And the calculated values are deflection, ISM(Impact Stiffness Modulus), LTE(Load Transfer Efficiency). The equivalent linear temperature difference represents the behavior of the concrete slab by the environmental load, and the calculated values by the HWD test represent the behavior. Therefore, the purpose of this study is to investigate the behavior of concrete slab by combined load including environmental load and traffic load through correlation analysis between these values. This study was supported by Incheon International Airport Corporation(BEX00625) and Korea Airports Corporation.

Airport concrete slabs behave by combined loads including environmental loads and traffic loads. To analyze the behavior of concrete slabs by combined load, the dynamic strain gages were embedded at 2 depths(50mm, 450mm) and 3 locations(corner, Center and Mid-Edge). And the thermometers were embedded at 5 depths(50mm, 150mm, 250mm, 350mm, 450mm) in actual airport concrete slabs. HWD(Heavy Weight Deflectometer) is a device to measure the deflection by applying an impact load. The values calculated by the HWD test are deflection, ISM(Impact Stiffness Modulus), LTE(Load Transfer Efficiency). Concrete slabs tend to expand during the summer when the temperature is high, and contract during the winter when the temperature is low. In addition, the drying shrinkage occurs as age increases. Field HWD test were conducted in March, May, August, and November to examine seasonal and age-specific changes. Furthermore, the temperature difference between top and bottom of concrete slabs causes the curl-up and curl-down behavior. The test was conducted 3 times at 12o`clock, 16o`clock, 21o`clock, 3o`clock, 7o`clock to examine temporal changes. The strain of the slab at HWD strike was measured 500 times per second because the strain occurred instantaneously, and the temperature was measure 1 times per 10 minutes. The calculated values and the measured values varied according to environmental loads. In order to examine these values in various angles, the equivalent linear temperature difference obtained by converting the temperature by depth into the uppermost lowermost temperature difference, the temperature of the slab which changes seasonally as a whole, and the drying shrinkage which occurs as the age increases are considered. Therefore, the purpose of this study is to clarify the behavior of concrete slabs by combined load considering long - term drying shrinkage, annual variation of temperature, and daily variations. This study was supported by Incheon International Airport Corporation(BEX00625) and Korea Airports Corporation.

In this study, proposed how to design an airport concrete pavement expansion joint considering the weather conditions and material properties. Currently, expansion joint spacing of airport concrete pavement in korea is not designed according to a clear standard, but it is designed to an empirical level. Various types of Admixture are used in concrete pavement and depending on the material characteristics or local environmental factors, there is a substantial difference in the extent and shrinkage to which the package is inflated. Significant differences are made in the extent to which the pavement expands or shrinkage depending on the material characteristics used or the local environmental factors. But, expansion joint design performed on empirical criteria cannot reflect these materials and environmental characteristics, resulting in unpredictable damage such as blow-up. To analyzing behavior of airport concrete pavement, horizontal displacement gauges, static strain gauges and thermometers are installed in the 3rd phase construction sites at Incheon International Airport. In this study, the relationship between the temperature and horizontal displacement of the concrete pavement was analyzed using the measured depth temperatures and the horizontal displacement data at the expansion joints at the Incheon airport site. The Finite Element Analysis Model of Incheon International Airport pavement was used to compare the difference between actual behavior and analytical behavior. In addition, it is proposed to design a suitable expansion joint spacing by considering the maximum expansion of concrete pavement and shrinkage caused by material expansion (e.g., ASR) and shrinkage due to water loss. This study was supported by Incheon International Airport Corporation (BEX00625).

In this study, the effect of dry shrinkage of concrete pavement due to seasonal changes was analyzed by comparing the results of finite element analysis with the temperature and strain measurements at Incheon airport pavement. To measure the behavior of slab by environmental condition in site, static strain gauges and thermometers were installed. To predict changes in the properties of concrete slab, experiments were conducted in site as well as in the lab. The considered parameters of FEA were pavement conditions according to seasonal and material properties change. The results of field measurements and the strain by FEA analysis were different in terms of the effects of drying shrinkage. This is due to humidity changes not applied to input values during FEA analysis. In this study, the difference between the results of field measurements and the results of the finite element model analysis was used to identify the drying shrinkage occurring on the concrete slab. Long-term data analysis in the future will enable the analysis of the trends in drying shrinkage in airport concrete pavement. This study was supported by Incheon International Airport Corporation(BEX00625).

PURPOSES : The purpose of this study is to develop a regression model to predict the International Roughness Index(IRI) and Surface Distress(SD) for the estimation of HPCI using Expressway Pavement Management System(PMS).METHODS : To develop an HPCI prediction model, prediction models of IRI and SD were developed in advance. The independent variables considered in the models were pavement age, Annual Average Daily Traffic Volume(AADT), the amount of deicing salt used, the severity of Alkali Silica Reaction(ASR), average temperature, annual temperature difference, number of days of precipitation, number of days of snowfall, number of days below zero temperature, and so on.RESULTS : The present IRI, age, AADT, annual temperature differential, number of days of precipitation and ASR severity were chosen as independent variables for the IRI prediction model. In addition, the present IRI, present SD, amount of deicing chemical used, and annual temperature differential were chosen as independent variables for the SD prediction model.CONCLUSIONS: The models for predicting IRI and SD were developed. The predicted HPCI can be calculated from the HPCI equation using the predicted IRI and SD.