Ground subsidence can result in the formation of sinkholes, potholes, settlement of structures, and road subsidence. Road subsidence is described as the sudden collapse of the road surface into subsurface cavities caused by the loss of bearing capacity in the ground, such as the dissolution of limestone by fluid flow in the surface causing the formation of voids leading to subsidence at the surface. Road subsidence occurs about 665 times annually, and this incidence has been increasing until 2013. Damaged underground facilities, management negligence, and lowering of the ground water table have been the causes of road subsidence in Seoul. Seoul metropolitan government announced special management counter plans to relieve the anxieties and make the roads safe for passing. Construction sites, such as excavation works, need to be managed properly because they have strong potential to induce road subsidence. The aim of this study was to identify the main causes of road subsidence and suggest management plans. First, life cycle cost analysis revealed the daytime construction to be more appropriate than nighttime. In addition, by analyzing the limitations of using sand as a backfill material, it is proposed to use a flowable backfill material instead of sand. Finally, to reduce the blind spots, which is a problem in surveying the road pavement conditions of local governments, the road to be managed is divided into several zones, and a specialized agency is selected for each zone and a method of surveying the blind spots through collaboration is suggested.

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Conventional asphalt concrete pavements have deteriorated rapidly due to the current increased traffic and extreme climate impacts. In addition to the upgrading in the construction quality, there is an urgent need to expand the utilization of modified asphalt binders to improve road capacity and traffic safety. The proposed research aims to combine epoxy resin (ER) and crumb rubber powder (CRP) contents into conventional Styrene-butadiene-styrene (SBS)-modified asphalt binder to not only reduce the consumption of normal asphalt binder but also promote the usage of recycled waste material in practice. To cope with this research objective, the ER and CRP were designed at 3% and 5% by weight of asphalt binder, respectively. Various laboratory tests were performed to evaluate the performance of modified mixtures (ERCRP), including the Frequency Sweep Test, Multiple Stressed Creep and Recovery, Dynamic Modulus, Semi-Circular Bending (SCB), and Cantabro Durability Tests. Additionally, an assessment of the modified asphalt concrete pavement via field testbed was conducted through Falling Weight Deflectometer and Ground Penetrating Radar. Overall, by adding the ER and CRP, the strain value of the control reference mix can be reduced up to 31.8% and 28.3% at MSCR 0.1 and 3.1 kPa, respectively. Additionally, the dynamic modulus of the ERCRP-modified samples was approximately 32,267 and 189 MPa, while the value of the reference mixture was 28,730 and 105 MPa at the highest and lowest frequency, respectively, indicating an enhancement under repeated loads. Regarding the SCB test results at 0 °C, the peak stress of the ERCRP-modified mixture was 4.75 MPa, while the value of the reference specimens was only 4.2 MPa, noticing the improved stress-bearing capacity. Based on a full-scale testbed, the FLWD elastic modulus of reinforced pavement shows a novel improvement (6.75%) compared with the control pavement, suggesting a potential application of ERCRP-modified asphalt binder for sustainable development purposes.

Recently, the number of potholes in the principal cities of korea has been increased because of the rapid climate change and the city population concentration. This study is to predict the number of potholes occurred in the Seoul metropolitan area. The prospective models for the pothole can help preventing the risk factors for the pothole. To finding the effect elements for the pothole occurrence, the empirical approach regarding the road engineering and analytical approach with stochastic analysis were used. The design of experiment regarding the surface response method was used to constitute the predictive model. The primary factors were utilized in the constitutive equation model using the multi regression analysis. The empirically predictive model makes little odds in p-value, coefficient of determination value and root mean squared error compared to the analytically predictive model. But, the analytical model has a lower incidence of error than the empirical model when the MPE(Mean Percentage of Error) analysis related to the maximum and minimum MPE was conducted.

The purpose of this research was to promote the recycling of pellet asphalt with Crumb Rubber Modifier (CRM) and Graphite Nanoplatelet (GNP) in pothole restoration. In this study, several laboratory tests were carried out on mixes containing CRM content ratios of 5%, 10%, and 20% and GNP content of 3% and 6% in order to identify the ideal mixing ratio of pellet-type asphalt paving materials. The Marshall stability test, the Hamburg wheel tracking test, and the dynamic modulus test were all performed to compare the effectiveness of the proposed method and heated asphalt combinations. Afterward, the full-scale testbed was conducted to verify the practical application between the proposed method and popular pothole-repairing materials. Both laboratory and field test findings confirmed that the asphalt pavement using 5% CRM and 6% GNP improved the resistance to plastic deformation and anti-stripping compared to the generally heated asphalt paving material, thereby extending road life. However, the resistance to fatigue cracking can be slightly reduced by incorporating these additives. Overall, the CRM and GNP asphalt pellet approach is a feasible solution for sustainable pavement maintenance and rehabilitation, particularly in small-scale damage areas such as potholes.