• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.111-119
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• 2011

Recently, urban redevelopment programs and expansion of social infrastructure have caused massive amounts of construction waste in construction fields, and the mounds of it keep increasing every year. The disposal of construction waste is emerging as a national and social issue and the recycled powder generated by the treatment process of waste concrete is all being abolished or buried. Therefore, the purpose of this study is to utilize waste sludge generated by the wet-type treatment process of waste concrete as materials(binder, filler) for cement composite. This study evaluates physical and mechanical properties of mortar using recycled powder according to heating temperature, contents and applications. As a result of the chemical analysis, recycled powder is composed mainly of CaO and $SiO_2$, and that it is even lower in the content of CaO than OPC. The charateristics of mortar using recycled powder, according to drying and heating temperature, shows that as the heating temperature increases, flow decreases. Also, compressive strength and porosity of mortar using recycled powder was superior when heating temperature was $600^{\circ}C$. Thus, it is revealed that an effective development of recycled powder is possible since the binder by cement composite recovers a hydraulic property during heating at $600^{\circ}C$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.487-496
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• 2017

Ground moving target indicator(GMTI) using syntheticaperture radar(SAR) used for finding moving targets on wide background clutter in short time is one of good ways to monitor a traffic situation or an enemy's threat. Although displaced phase center antenna (DPCA) is a real time method with low computational complexity, there have been few studies about its performance against various ground clutters. Thus, we need to analyze GMTI performance for various ground clutters in order to design a suitable DPCA detector. In this paper, simulation results show that the conventional DPCA detector produces different performance in terms of detection rate and false alarm rate. In particular, the false alarm rate of heterogeneous or extremely heterogeneous clutter from urban area is higher than one of homogeneous clutter from natural area.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.65-73
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• 2020

This study describes the evaluation results of pile length ratio and N value on the bearing capacity of drilled shafts in cohesionless soil. The bearing capacity ratio in Meyerhof's formula is affected only by the length ratio, and it is equally evaluated a sharing ratio of the end bearing capacity and the skin friction. NAVFAC's formula shows that the pile length influences both end bearing capacity and the skin friction, but pile length is also found to be a more influence factor on the end bearing capacity. Especially, it was found that the effect of pile length factor was larger than the effect of N value and pile diameter. FHWA's formula was evaluated to reflect the influence factor by skin friction more positively than other formulas at calculation the bearing capacity. It was also confirmed that the influence of the skin friction is larger when the ultimate bearing capacity is evaluated.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.775-784
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• 2009

Weathered foliation could act as a critical failure plane because this type of plane tend to have low roughness and long extensions. A big constructed slope at $\bigcirc\bigcirc$ road construction site was failed due to the block movement along a fault zone which is parallel to foliation. Tectonic activity reactivated a fault zone parallel to foliation, and the fault clay within the shear zone metamorphosed retrogressively to chrolite. The failed block moved when the block weigh lost the balancing with the resisting force of the retrogressively metamorphosed chrolite. Evaluating the three dimensional distribution of the foliation was critical for establishing a plan for the stabilization of the slope. For this purpose, 10 boreholes were drilled as a lattice distribution, and the BIPS analyses are performed at each boreholes. The fractures measured in the boreholes are projected into 15 cross sections and their distributions are analysed, using Fracjection software. The projection analyse show that the strike of the foliation gets dipper towards left side of the slope. This geometry indicates that there are more failure block geometry at left side of the slope. Potential failure planes are searched using the projection method, and these information are provided for further support design.

• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.19-29
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• 2012

Pack micropiles were recently developed to improve pile capacity of general micropiles. Pack micropiles were made by warping thread bar or steel pipe of general micropile by geotexlile pack and grouting inside the pack with pressure. According to the pressure, the boring hole could be enlarged. A series of pile uplift tests were performed on three micropiles. Two out of the three piles were the pack micropiles and the other was the general micropile, in which a thread bar was used in the boring hole. According to the pressure applied to the pack micropiles, the diameter of boring hole was enlarged from 152 mm to 220 mm. Unit skin friction mobilized on side surfaces of micropiles increased with displacement of pile head and reached on a constant value, which represents that the relative displacement between piles (or thread bar) and soils was reached on critical state. And the uplift resistance of pack micropile was higher than that of general micropile. Two reasons can be considered: One is that the frictional surface increases due to enlarging diameter of boring holes and the other is that the unit skin friction could increase due to compressing effect of surrounding soils by soil displacement as much as the enlarging volume of boring hole. The compression effect appeared at deeper layer rather than surface layer. The unit skin friction mobilized on micropiles with small diameter was higher than the ones on large bored piles.

• Resources Recycling
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• v.27 no.2
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• pp.38-47
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• 2018

Integrated gasification combined cycle (IGCC) is a next generation energy production technology that converts coal into syngas with enhanced power generation efficiency and environmental performance. IGCC produces almost coal gasification slag as the solid by-product. IGCC slag is generated about 140,000 tons for a year although recycling of it is still in the early stages. We evaluated the potential of IGCC slag which is generated from a pilot plant in South Korea as an alkali-activated cement. Samples which were activated with the combined activator of sodium silicate solution and caustic soda had an average compressive strength of 4.5 MPa, showing expansion. Expansion of the alkali-activated slag was presumed to be caused by free CaO in the slag, although it was not detected by the ethylene glycol method. Samples that were activated with the combined activator of sodium aluminate and caustic soda had an average compressive strength of 10 MPa. Hydroxy sodalite and $C_3AH_6$ were found to be the new crystalline phases. IGCC slag can be used as an alkali-activated material, but the strength performance should be improved with proper mix design approach to calculate optimum proportions which can alleviate the expansion issue at the same time.

• Korean Journal of Construction Engineering and Management
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• v.18 no.3
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• pp.52-62
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• 2017

The purpose of this study is to develope an assessment method for parking lot remodeling alternative by adopting the asset management technique. In order to identify the Level of Service(LOS) and the Evaluation Measurement(EM), literatures was implemented which documented the consideration of parking lot plan, needs of the apartments' tenant, and various design standards. In addition, the authors conducted a three-time delphi survey for the identified 5 LOS and 19 EM to evaluate suitability and necessity of them and to collect additional opinion of experts. The LOS of parking lot were categorized into 5 areas such as Environmental effect and Convenience, Accessibility and so on. The 19 EM were determined to estimate the LOS quantitatively. The researchers analyzed the degree of importance of LOS and EM by using the Analytic Hierarchy Process (AHP) method. But construction cost was excepted from the analysis, because it is used as an independent variable in alternative assessment. In conclusion, the authors proposed the estimation criteria for EM, and the method and process for alternative assessment be performed to benefit-cost analysis using the LOS variation and construction cost. The assessment method for parking lot remodeling alternative was demonstrated effective to assess the parking lot remodeling alternative by case-study. This study has a academic significance by adopting the asset management techniques in the area of the parking lot remodeling. And the assessment method is expected to help deciding a reasonable remodeling alternative of parking lot, as it ensures the diversity for remodeling of the parking lot and reflects the needs of the occupant.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.5
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• pp.779-797
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• 2017

Recently, underground road construction is attracting attention because the ground transportation facilities in the urban area have reached the saturation level and traffic volume has increased and the air pollution has risen. Construction of underground roads is not only reduce trafficjam in downtown but also design the city eco-friendly, so existing roads as well as new roads go underground. It is essential to construct divergence tunnels that serve as IC (interchage) and JC (Junction) when constructing underpasses. Therefore, the analysis of the effect of the existing tunnel by the divergence tunnel should be considered. In this study, numerical analysis is performed to analyze the effect of existing tunnel on the excavation of the divergence tunnel. The divergence tunnels were set in 5 cases at $45^{\circ}$ intervals in the clockwise direction starting from the lower part of the existing tunnel. In each case, numerical analyses were carried out by using the DCM (Displacement Controlled Model) for applying the volume loss of 0.5%, 1.0% and 1.5%. As a result, when the volume loss increased, the effect on displacement, fracture range, and effect on stability increased as well. In addition, it was confirmed that the divergence tunnel located directly underneath is the weakest for the stability, and the case where the divergence tunnel is located diagonally rather than the vertical and horizontal direction is found to be vulnerable to displacement and lining destruction.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.669-675
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• 2020

In this study, 3D analysis was compared in evaluating the track deformation of subway structures during adjacent excavation. For the 3D analysis model, the boundary conditions of the tunnel model and the application level of the ground water were analyzed as variables. As the result of the effects of track irregularity using the 3D model, the analysis model considering the site ground water level instead of the design values and changing the constraint of the boundary condition is more reasonable. In addition, the influence of track irregularity due to the boundary condition and load condition of the analytical model is more obvious in the factors directly affected by the longitudinal relative displacement of the rail, such as alignment, cross level and gauge irregularity. Therefore, the evaluation on track stability according to adjacent excavation work was appropriate to analysed the longitudinal deformation of the track by using 3D model that could be investigate the deformation of rail. In addition, the boundary condition and load condition(ground water level) of the numerical model was important for accurate analysis results.

• Korea journal of population studies
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• v.28 no.2
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• pp.205-217
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• 2005

Purpose: To evaluate the factors affecting hospital utilization for respiratory diseases by ecological study design and GIS tool. To raise the social concern for respiratory disease by the result. Methods: Hospital admission data supported by national health insurance cooperation were transformed to spread sheet data format and combined with air monitoring dataset. Air pollution data were collected from the annual report of air monitoring published by Korea Ministry of Environment. Socioeconomic statistics including population density, age distribution, forest ratio etc.. were filed using Korea National Statistical Office database. Multiple linear regression analysis was performed to evaluate the factors affecting hospital utilization for respiratory diseases. Analytical unit was 52 cities. Results: The factors affecting hospital utilization for respiratory diseases were the proportion of population 60 years and over, seaside city, $O_3$ level, smoking rate. Conclusions: However, outdoor pollutants monitoring data and smoking rate have weakness in reflecting individual exposure. Further research is required to propose more illustrative means to evaluate causal relationship between air pollution and respiratory health effect factors.