PURPOSES: The purpose of this study is to evaluate the long-term physical and mechanical properties of domestic asphalt binders.
METHODS: The physical properties are evaluated by penetration, softening point, penetration index, and binder viscosity. The mechanical properties were confirmed by the changes of G*, phase angle (δ), stiffness, and m-value.
RESULTS: The physical properties of the asphalt binder were not clearly distinguished. In the case of G* flowing after using a pressure-aging vessel, the two types of PG 64-22 (a paving asphalt) showed similar results. However, the PG 76-22 binder was confirmed to have variations in value. The two types of PG 64-22 showed stiffness changes over time at the lowest temperatures, whereas the PG 76-22 binder maintained a constant range of change and exhibited stable behavior.
CONCLUSIONS: The PG 76-22 binder showed stable behavior across physical and mechanical properties, but PG 64-22 binders showed viscosityy changes in some sections.
PURPOSES: The purpose of this study is to identify the mechanism of road subsidence caused by damaged water and sewer pipes.
METHODS: A series of soil chamber test using damaged water and sewer pipe models were conducted under various conditions.
RESULTS : Characteristics of cavity expansion and collapse caused by damaged pipes were affected by the damaged location in the sewer pipe, the head on the water pipe, the distance between the damaged water pipe and outlet, and relative soil density.
CONCLUSIONS: Sewer-pipe damage was considered a direct cause of road subsidence, and the cavity expanded discontinuously. When the outlet was located under the damaged water pipe, the cavity expanded in the water pipe’s direction, and collapse occurred above the pipe. However, when the outlet was located atop the damaged water pipe, the cavity expanded toward the outlet direction and resulted in a subsidence. Cavity expansion speed was affected by various conditions, such as the pipe’s water head, outlet position, distance between the damaged water pipe and outlet, and relative soil density. However, the cavity expansion shape did not affect factors, except for outlet position.
PURPOSES: The objective of this study is to evaluate road subsidence based on model chamber tests.
METHODS : A theoretical review of road subsidence mechanisms was carried out, and a series of soil chamber tests with initial cavities were conducted under various conditions. Road subsidence risk was analyzed based on these results.
RESULTS: The cavity collapse risk was affected by multiple factors, including cavity location, traffic loading, and asphalt layer thickness. The Nf number of loading required to reach cavity collapse increased as the cavity width increased, cavity depth decreased, and asphalt layer thickness increased.
CONCLUSIONS: The effects of asphalt thickness on the risk of road subsidence was assessed to have an additional 1.5-fold effect on the subgrade thickness. This study proposed an effective cavity depth (Deff), considering the strength of the asphalt layer. Based on the results of the model chamber test, a four-class road subsidence risk model was proposed with effective cavity depths and widths. It was found that the risk of road subsidence increased as the cavity width increased and the effective cavity depth decreased. This trend is also well matched to the road subsidence risk models of Japan and Seoul.
PURPOSES : Exposed aggregate concrete pavements have been adopted in several countries because of their advantages of pavement texture characteristics, which can produce low tire-pavement noise and higher load-carrying capacities. The magnitude of tire-pavement noise greatly depends on the wavelength of pavement texture. The wavelength of exposed aggregate concrete pavement can be controlled with maximum sizing and by controlling the amount of coarse aggregates in the concrete mixture. In this study, the maximum size and the amount of coarse aggregate in the exposed aggregate concrete pavement are investigated to produce equal levels of wavelength in the asphalt pavement.
METHODS: A simple method to measure the average wavelength of pavement texture is introduced. Subsequently, the average wavelength of typical asphalt pavement is investigated. A set of mixture designs of exposed aggregate concrete with three maximum-sized coarse aggregates, and three amounts of coarse aggregate are used. The average wavelengths are measured to find the mixture design needed to produce equal levels of wavelength as typical asphalt pavement.
RESULTS : With a cement content of 420 kg/m3 and fine aggregate modulus of 30%, the number of exposed aggregates was 48, and the shortest texture depth provided a wavelength of 4.2 mm. According to the number of exposed aggregates, the exposed aggregate concrete pavement could be rendered low-noise, because its wavelength was similar to that of asphalt pavement ranging from 3.9 to 4.4 mm.
CONCLUSIONS : Selection of appropriate maximum sizes and the amount of coarse aggregates for exposed aggregate concrete pavement can produce a wavelength texture closely resembling that of asphalt pavement. Therefore, the noise level of exposed aggregate concrete pavement can be reduced with an appropriate maximum size and the amount of coarse aggregates are employed.
PURPOSES : This study aims to evaluate the applicability of ground penetrating radar (GPR) for surveying utility pipes under sidewalks made of concrete brick and plate-stone block pavements.
METHODS : GPR tests were conducted at two test sections to detect layer boundary and utility pipes under the pavements. The central frequency of the single-channel GPR was 800, 500, 250, and 100 MHz, and the central frequency of multi-channel (8) GPR was 450 MHz. GPR signals were analyzed in terms of 1-D (A-scan) and 2-D (B-scan) profiles.
RESULTS: From the A-scan data analysis, the vertical resolution of the GPR ranged from 7.3 cm for 800 MHz to 133.1 cm for 100 MHz in the concrete brick block pavement and 13.9 cm for 800 MHz to 144.2 cm for 100 MHz in plate stone block pavement. From the B-scan data analysis, 250 MHz to 500 MHz GPR was sufficient to differentiate the layer boundary at a depth of 1.0~1.5 m to detect utility pipes at a depth of 0.5~2.0 m in both block pavements. In the plate-stone block pavement, GPR signal attenuation was greater because of the wire mesh in the concrete layer. Thus, the penetration depth was approximately 80% of the concrete brick-block pavement.
CONCLUSIONS : The penetration depth and vertical resolution of GPR in the sidewalk paved with blocks were comparable to those of roadway pavement. Among the GPR evaluated, the 250 MHz GPR was the most desirable, and the 500 MHz GPR was affordable for the investigation of underground pipes situated up to 2.0~3.0 m under sidewalks.
PURPOSES : This study compares the results of field-monitored unsaturated hydraulic data to verify the wetting path estimation method using the drying path on roadside soil slope.
METHODS: A method proposed by Fredlund was used to estimate the wetting curves of soil water characteristic curves. Wetting curves were estimated from the drying curve acquired mainly from laboratory testing, and the estimated wetting curve was applied to the infiltration analysis to verify the estimation method. The infiltration analysis results obtained from the drying, wetting, and estimated wetting curves were compared to the field-monitored data at the same location.
RESULTS : The volumetric water contents measured at 40 cm were closest to analysis results obtained from the wetting curve, whereas the volumetric water content measured at 80 cm were closest to the analysis results obtained from the drying curve. The results of the estimated wetting curves were between the results of the drying and wetting curves. The measured suction results were within the drying and wetting curves, and the estimated wetting curves were within the drying and wetting curves. Additionally, the safety factor obtained from applying the drying curves was carefully calculated, and the factor of safety of the estimated wetting curves was close to the results of the wetting curves.
CONCLUSIONS : Applying a drying curve to calculate the slope stability during the rainy season will cause an overestimation of the factor of safety at roadside soil slopes. However, if the proposed estimation method of the wetting curve can be applied to the numerical analysis, the stability of the road slope can be reasonably estimated.
PURPOSES: The objectives of this study are to analyze the current status of pothole during a rainy season and to suggest a future pavement maintenance method via pothole analysis.
METHODS: Potholes are caused by moisture submerged in pavement. The pore pressure caused by traffic and environmental loads causes failure between the aggregate and asphalt binder. Thus, heavy rain is a primary pothole creator, especially in aged pavement. To prevent accidents on roadways, Gyeonggi-do has initiated a fast pothole repair program. However, the number of potholes increase every year. In this study, the current status of potholes and maintenance methods are analyzed. Based on these results, a future pavement maintenance method is suggested.
RESULTS AND CONCLUSIONS : Gyeonggi-do’s pothole situation is worse than Seoul’s. Problems were founded, as follows. The amount of potholes was large, and the number increased annually. Pothole management is done at a basic level, because there is no long-term plan. Potholes occur frequently at the same site because of the poor quality of emergency repair. Finally, there is no systematic and comprehensive pavement management. Thus, pothole prevention measures are ill-prepared. Therefore, to reduce potholes and to manage high quality pavement, it is necessary to make a long-term pavement management plan.
PURPOSES : With the recent change to domestic and overseas construction technologies, which led to the adoption and application of threedimensional building information management (BIM), a BIM output delivery operation system is needed for the civil engineering infrastructure category. This study analyzes the domestic and overseas BIM-order placement, BIM-related guidelines/guides, and the BIM output delivery system for the road construction project category to present guideline development measures for BIM output writing and delivery.
METHODS: This study surveys and analyzes the domestic BIM-related research trends to examine the domestic-infrastructure BIM-order placement situations in public ordering agencies. Additionally, it analyzes the domestic BIM-related guides and guidelines and existing twodimensional electronic delivery systems and the domestic and overseas BIM output delivery systems. This study defines the guideline composition system and direction to present criteria for BIM output writing, delivery, management, and utilization in the road category. Furthermore, it presents guideline composition measures for BIM output writing and delivery to propose detailed criteria, output-list composition, and output inspection procedures.
RESULTS : This study presented BIM output guideline development measures for planning BIM output writing and delivery and management/utilization measures in the road category. To that end, it determined the domestic and overseas BIM guide and guideline composition systems, BIM ordering criteria, BIM data writing and delivery criteria, BIM output management and utilization measures, and a common BIM output list to present suitable detailed criteria.
CONCLUSIONS: This study sought to respond to changes to the domestic and overseas construction environment and to present output writing/delivery guidelines as activation measures supporting the adoption and application of BIM. To that end, we analyzed the domestic and overseas BIM guidelines and guides, task instructions, bid information, etc. to define the appropriate composition system and to give it direction. We defined the contents of tables and detailed descriptions to present guideline development measures for BIM output writing/delivery guidelines in the road category. This is expected to improve work efficiency for BIM and to enhance output quality and utilization. Furthermore, the adoption of BIM in the road category will provide an infrastructure environment with which to exchange BIM information with related agencies. We plant to further develop verification tools for the Ministry of Land, Infrastructure, and Transport's BIM model projects, for their output writing and delivery, and for an integrated BIM platform that will continue to improve the proposed criteria.
PURPOSES : This study aims to propose widths of pedestrian zones considering the characteristics of sidewalk areas, pedestrian volumes, and pedestrian density.
METHODS : We derived a pedestrian zone formula considering the maximum pedestrian volumes, mean intervals between pedestrians (pedestrian density), occupancy widths of pedestrians, and average speed of pedestrians. We compare the widths obtained using the formula with the existing Korean standards.
RESULTS: Considering the pedestrian volumes and density, the pedestrian zone widths of neighborhood main sidewalk areas are determined to be 1.4~4.5 m, whereas those of commercial sidewalk areas are determined to be 1.4~2.9 m.
CONCLUSIONS: Existing Korean regulations and guidelines provide a uniform standard sidewalk width. However, this study proposed a formula for determining pedestrian zone widths considering pedestrian volumes, characteristics of the sidewalk area, and pedestrian density.
PURPOSES : The impact of traffic accidents varies with the change in the social background of drivers. Thus, this study analyzes the characteristics of traffic accidents caused by taxis based on factors such as the type of taxi owner, driver’s age, and length of driver’s career and consequently suggests improvement methods.
METHODS: Based on the data of the accidents involving taxis registered in Seoul, this study analyzed traffic accidents by categorizing taxis by the type of owner, driver’s age, and length of driver’s career. For statistical verification, SPSS was used to derive the influence variables through polynomial logistic regression analysis, and accordingly, a method to reduce traffic accidents caused by taxis was proposed.
RESULTS: In the case of aged drivers and drivers with long careers, vehicle-to-vehicle accidents accounted for a lower percentage than other accidents; moreover, the accident rates in downtown and that at nighttime were high. Drivers with long careers had a lower percentage of selfinjury; however, as the total number of deaths and serious injuries caused by such drivers was higher, there is a greater risk of serious accidents caused by them.
CONCLUSIONS: This study analyzes the characteristics of taxi accidents based on the type of taxi owner, driver’s age, and length of the driver’s career to determine the periodical characteristics of taxi accidents in aging society. Therefore, the number of traffic accidents caused by taxis can be drastically reduced if the results of this study are used in the customized safety education of drivers and improvement of traffic facilities.
PURPOSES : The purpose of this study is to develop a service volume for signal metering on roundabouts to increase applicability of roundabout in Korea.
METHODS: To develop the service volume for signal metering on roundabouts, traffic simulation studies were conducted using VISSIM software for various scenarios based on traffic volumes as approaches and location of detectors on controlling approach lane. Typically, the Vehicle Actuated Programming module in VISSIM was applied for analyzing more realistic traffic signal control conditions.
RESULTS: As the left-turning volume is increased, the delay reduction rates were increased. And the case of 40 meter distance of a detector and 20 seconds red signal phase made better results.
CONCLUSIONS: The signal metering on roundabout should be applied carefully because it is possible to lose roundabout strengthen in traffic operation aspect. The service volume for signal metering on roundabouts that suggested from this study is useful to decide the application of signal metering on roundabout.