• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.317-327
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• 2013

Air pollution and artificial heat of urban areas have caused the urban heat island in which asphalt pavements absorb solar heat during the daytime and release the heat at night. Hence, in order to improve the environment of urban areas, it is necessary to examine cooling pavements that can reduce heat on road pavements in urban areas. The application of temperature insulation paints on road pavements require to reduce black brightness for visibility, to increase the reflection rate of infrared light and minimize the reflection rate of visible light. In the study, one part of Acrylic-emulsion was used as a main binder, and the changes in black brightness and the changes of addition ratio (0%, 15%, 30%) of hollow ceramics, as well as kinds of paints (carbon black pigment, mixed mineral pigment) were selected as the main experimental factors. The performance of temperature reduction of cooling pavements was analyzed through the reflection rate of spectrum, the reflection rate of solar heat, and the lamp test. Abrasion resistance, UV accelerated weather resistance, and sliding resistance were tested in real situations. In addition, the performance of heat reduction of testing pavements covered with high-reflection paints was analyzed by using an infrared camera. As the test results, when using mixed mineral paints and hollow ceramic of 30%, the reflection rate of spectrum was 43% in the area of near-infrared ray and 17% in the area of visible light at black brightness of $L^*$=42.89 and the reflection rate of solar heat was 27.5%. Total color difference was ${\Delta}E$=0.27 in the test of UV Accelerated Weather Resistance, indicating almost no changes in color. BPN was more than 53 when scattering #2 and #4 silica sand of more than $0.12kg/m^2$. In Taber's abrasion resistance test, abrasion loss was up to 86.4mg at 500 rotations. The performance of heat reduction was evaluated using an infrared camera at the test section applying high-reflection paints to asphalt pavements, in which the results showed that the temperature was reduced by $12.7^{\circ}C$ on CI-30-40 cooling pavements ($L^*$=38.76) and by $14.2^{\circ}C$ on CI-30-60 cooling pavements ($L^*$=57.12).

• Journal of the Korean GEO-environmental Society
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• v.15 no.12
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• pp.117-128
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• 2014

Generally, when constructing a tunnel close to existing structures, the tunnel must be built at a constant distance from the structures that is more than width of tunnel to minimize the impact of interference between an existing structures and new tunnel. Spacing of these closed tunnels should be designed considering soil state, size of tunnel and reinforcement method. Particularly when the ground is soft, a care should be taken with the tunnel plans because the closer the tunnel is to the existing structures, the greater the deformation becomes. As methods of reviewing the effect of cavities on the stability of a tunnel, field measurement, numerical analysis and scaled model test can be considered. In the methods, the scaled model test can reproduce the engineering characteristics of a rock in a field condition and the shape of structures using the scale factor even not all conditions cannot be considered. In this study, when construction of a tunnel close to existing structures, the method and considering factors of the scaled model test were studied to predict the actual tunnel behavior in planning stage. Furthermore, model test results were compared with the numerical analysis results for verifying the proposed model test procedure. Also, practical results were derived to verify the stability of a tunnel vis-a-vis cavities through the scaled model test, which assumed spacing distances of 0.25 D, 0.50 D, and 1.00 D between the cavities and tunnel as well as the network state distribution. The spacing distances of 1.0 D is evaluated as the critical distance by the results of model test and numerical analysis.

• Journal of Soil and Groundwater Environment
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• v.6 no.4
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• pp.61-72
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• 2001

A barrier liner system is placed at the bottom and side slope in landfill to protect a leaking of leachate that the hydraulic conductivity of this system should be less than It 107cm/sec. In this study, the soil-bentonite mixture for the bottom liner system was evaluated in two point of views : changing characteristics of the hydraulic conductivity according to the different mixing ratio of soil-bentonite with the effect of bentonite swelling and the difference method (A & D type) of compaction on the hydraulic conductivity. As the results, maximum dry density (${\gamma}$$_{dmax}$) of SC group mixture was higher than of CL group mixture. However, the result of optimum moisture contents(OMC) of both groups were the contrary. In case of ${\gamma}$$_{dmax}$ by different compaction method, D type was higher than A. But the OMC were the contrary. The difference of ${\gamma}$$_{dmax}$ according to the Compaction energy, “SC” group mixture W3S higher than the “CL” group. In case of OMC of “CL” group was higher than “SC” group. The effecting of swelling was a little bit different on the two factors. According to the result of compaction test, the use of site soil only could not meet the criteria on hydraulic conductivity, but could find a solution for the mixing ratio of bentonite mixture were satisfied to the standard of barriation. The increased in bentonite mixing ratio and degree of swelling, the values of hydraulic conductivity were decreased. Especially the “CL” group with “D” type compaction measured the lowest value with the same conditions. Also, the bentonite mixing ratio has more influenced on the hydraulic conductivity compare with swelling effect. The “SC” group mixture with “A” typo compaction got a big difference from others. The evaluation of economic for the construction cost on the two cases, the lower bentonite mixing ratio of soil-bentonite mixed soil is more economically because of bentonite cost.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.2
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• pp.47-61
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• 2009

The purpose of this study was to understand the laws related to the safety management of children's play facilities(LRSMCPF) including the "Safety Supervision Law of Children's Play Facilities(SSLCPF)" and the "Quality Management and Industrial Products Safety Management Law(QMIPSAL)", in order to analyze the problems by 4 phases-development of products, landscape design, landscape construction and maintenance considering landscape project procedure-and to propose a revision of the laws. The results are as follows: 1. The various LRSMCPF, SSLCPF and QMIPSAL, as basic laws for the safety management of children's play facilities, were insufficient regarding the features of children's play facilities and play spaces, which are both comparatively varied and complex. 2. In development of products, the one-year duration of safety certification based on QMIPSAL was too short and the procedure for safety certification were redundant in both products and plants inspection, and export and import product inspection. 3. The field inspection of construction sites based on SSLCPF was repeated with quality control and a consultation of rules based on "Construction Technology Management Law". 4. There are not enough safety inspection organizations regarding children's play facilities to meet the demand of safety certification, safety inspection, and safety education in the near future. 5. For children's play safety, the establishment of a general safety management system for children's play connected with the phases is needed to ensure safe play equipment, to construct safe playgrounds, and to manage play facilities. The criteria, regulations, and procedure regarding safety certification and safety inspection of play facilities must be revised efficiently and standardized to a global level as well. To improve the system and contents of safety certification and inspection, authorization of safety inspection organizations based on landscape architecture is needed. Further study will be required to concretely analyze in detail the laws, enforcement decrees and rules, and ordinances that consider the practical experience of professional landscape architects, inspectors, and lawyers.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.6
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• pp.150-159
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• 2015

This study was conducted for the purpose of presenting basic data for calculating a more reasonable landscaping project cost in the future through the construction cost calculation ratio of scenic planting and facilities and their time series trend analysis targeting 'J' corporation, a representative Korean public institution that creates apartment complexes. This study targeted scenic planting and the facility construction costs of 37 apartment complexes in the capital area from 2004 to 2012, using statistical analysis methods such as technical analysis, correlation analysis, and regression analysis to analyze the characteristics of the time series change. The conclusion was drawn as follows. First, breaking down the cost of overall landscaping projects to scenic planting and facility construction, the ratio of the average cost of scenic planting to that of facility construction showed 56.1% to 43.9% from 2004 to 2012. Second, the costs of planting construction and facility construction both showed a fluctuation range of about ${\pm}3%$, implying relatively steady costs considering the inflation rate. Third, the landscape construction cost for each type of construction resulted in a fluctuation range from minimum ${\pm}3%$(exercise facility) to maximum ${\pm}5%$(packing facility), reflecting that among the landscaping projects, the facility construction costs tended to show relatively large fluctuations in accordance with the change of time series. Fourth, the comprehensive indication of the ratio of landscaping project costs by time series and landscaping construction type implies that the regional characteristics and positional condition of the apartment complexes were not reflected sufficiently. Fifth, the high level of correlation of landscaping construction types and landscaping construction elements imply that the entire construction costs were controlled through partial adjustment of cost components within the overall frame of construction cost. These results reveal the problems of standardized landscaping cost irrespective of user satisfaction or environmental traits such as the conditions of the apartment complexes.

• Journal of the Korean Geosynthetics Society
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• v.17 no.2
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• pp.41-49
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• 2018

The purpose of this study is to fabricate a full scale road embankment using lightweight air foamed soil as a soil material on soft ground and to investigate its material characteristics and behavior in order to promote dredged soil utilization and minimize ground improvement. As a result of the laboratory test of the onsite mixed samples, the total unit weight of the specimens decreased almost linearly until curing 28 days. In particular, the total unit weight after 28 days of curing was reduced to about 81% of the slurry state before curing, which will be useful in the formulation of similar native soil materials in the future. The unconfined compressive strength began to decrease with the 14th day of curing as shown in the previous study. When the cement content is increased, the strength decreases sharply at a small strain change after the occurrence of the maximum compressive strength, and the maximum strength is exhibited in a range of a smaller axial strain than normal range. The settlement at the surface layer of the ground due to the lightweight embankment was about 1 / 2.75 of the soil embankment and was in agreement with the unit weight ratio (1 / 2.7) of the embankment materials. This indicates the cause and effect of the settlement due to the difference in self weight of the embankments. Also, the difference in settlement between soil and lightweight embankment increased with increasing depth. This shows that the difference in the point at which the settlement is terminated is clear. The ground horizontal displacement under the lightweight embankment was about 15~20% smaller than that of the soil embankment and the depth of occurrence was also 4.5~5.0m shallower in the lightweight embankment.

• Korean Journal of Construction Engineering and Management
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• v.12 no.6
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• pp.65-78
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• 2011

Construction business, which is complex and long-term business, requires accurate estimation and verification in construction costs and payment procedure from project planning to the completion of construction phase. And more importantly, it is necessary to investigate and determine the risk factors related to construction costs during the entire process including design planning, construction drawings, and quantity calculating. But, currently, it is not seem to be adequate to cope with the risk and increased construction costs against the operational budget in terms of actual costs when screening and estimating the bidding cost of public apartment. Therefore, this study selected and analyzed 40 sites' report of construction completion account from 2004 to 2010 focused on the adequacy on the modification of contract and design planning and on the complication of the budget in the beginning of the project. This study deducted various risk causes and results by analyzing actual costs according to year, architectural area, region, construction cost and sale/lease classification. We could find out construction risk according to annual variation of government policy and economy, and also deducted risk items by construction characteristic according to region and architectural area. Study result, we first found out the problems of lowest price award system according to the construction costs. The weight of the cost increase risk was analyzed that subcontract and material costs are very high. Roof and tile work were analyzed highly in subcontract cost risk and reinforcing bar and cement were analyzed highly in material cost risk, among direct construction cost. Finally, this study results could be used in comparing the categories of the construction costs made by specific construction process, belonging to the construction costs, with the operational budget made in the beginning of the project that can enable to grasp unpredictable risks over the construction costs and making quantitative analysis for it through analyzing the range of fluctuation and variations led by the fluctuations in the actual construction costs.

• Journal of Bio-Environment Control
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• v.29 no.4
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• pp.320-325
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• 2020

This study aimed to analyze thermo-keeping and economic feasibility by utilizing silica aerogel, which has been attracting attention as a new material, complementing the disadvantages of the conventional multi-layered thermal screen, and producing and installing multi-layered thermal screen. The multi-layered thermal screen used in the experiment was produced in two combinations using a non-woven fabric containing silica aerogel and measured and compared the temperature and fuel consumption changes due to differences in practice with the multi-layered thermal screen being sold and used on the market. Experimental results show that the temperature and relative humidity changes due to the differences of the multi-layered thermal screens in the single-span greenhouse and the multi-span greenhouse were small but remained almost the same temperature and relative humidity. It is judged that this shows that the multi-layered thermal screen using silica aerogel is not inferior to the conventional multi-layered thermal screen. As a result of a comparative analysis of heating energy, the aerogel-based multi-layered thermal screen reduced fuel consumption by about 15% in the single-span greenhouse and about 20% in the multi-span greenhouse compared to the conventional multi-layered thermal screen. It is clear that heating energy is saved as a greenhouse size and duration increase. It was found that the silica aerogel-based multi-layered screen was more breathable and warmer than the conventional multi-layered thermal screen, but It was found that the multi-layered screen used in the multi-span greenhouse was heavier and stiff compared with the conventional multi-layered thermal screen, indicating less workability and operability. Therefore, improvements were applied to the multi-layered screens used in the single-span greenhouses. It was confirmed that the replacement of internal insulation materials reduced thickness and improved stiffness so that there could be sufficient possibility for farmers to use.

• Korean Journal of Construction Engineering and Management
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• v.10 no.2
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• pp.65-74
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• 2009

It is expected that the number of apartment complexes in Korea that are over 20 years old will rapidly increase to more than 3,500,000. Consequently, the remodeling of these buildings is being revitalized throughout the country. Among the requirements for such remodeling, the expansion of parking lots has considerable weight. When enlarging a parking lot, the access route from an underground floor to the main building (i.e., the means of entry into the main building) determines the possibility of vertical enlargement for elevators, the size of the parking lot, the construction period, and construction expenses, etc. When enlarging an underground parking lot of an apartment complex, the access between the main building and the parking lot, as well as the inhabitants' requirements for entering the main building, are generally determined based on the designer's experience, rather than on the exact estimation of the peculiarity of the complex. In order to resolve such a problem, when enlarging an underground parking lot, a systematic and rational method is needed for selecting the means of entry into the main building. In this study, a selection model is derived for the method of selecting an access route into the main building when constructing an underground parking lot, in order to provide a reasonable decision-making process. A research method was investigated for determining the access route into the main building when enlarging a parking lot. On the basis of research carried out through in-depth interviews with experts, the characteristics for each means of entry into the main building were analyzed and the factors affecting the selection of the access route were deduced. The affecting factors selected were construction efficiency, convenience efficiency and economic efficiency. Weight values were then estimated for the selected affecting factors by applying the AHP method. Results showed that convenience efficiency, which gained the highest value, is the most important factor in selecting the means of entry into the main building. The most suitable means of entry into the main building was also suggested after estimating the applicability of the site by selecting complexes with remodeling possibility. This study will be applied as a reference for selecting the means of entry into the main building when constructing an underground parking lot particularly for older apartment complexes.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.37-47
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• 2017

In this study, a series of full-scale field tests on prebored and precast steel pipe piles and the corresponding numerical analysis have been conducted in order to study the characteristics of pile load-settlement relations and shear stress transfer at the pile-soil interface. Dynamic pile load tests (EOID and restrike) have been performed on the piles and the estimated design pile loads from EOID and restrike tests were analysed. Class-A type numerical analyses conducted prior to the pile loading tests were 56~105%, 65~121% and 38~142% respectively of those obtained from static load tests. In addition, design loads estimated from the restrike tests indicate increases of 12~60% compared to those estimated in the EOID tests. The EOID tests show large end bearing capacity while the restrike tests demonstrate increased skin friction. When impact energy is insufficient during the restrike tests, the end bearing capacity may be underestimated. It has been found that total pile capacity would be reasonably estimated if skin friction from the restrike tests and end bearing capacity from the EOID are combined. The load-settlement relation measured from the static pile load tests and estimated from the numerical modelling is in general agreement until yielding occurs, after which results from the numerical analyses substantially deviated away from those obtained from the static load tests. The measured pile behaviour from the static load tests shows somewhat similar behaviour of perfectly-elastic plastic materials after yielding with a small increase in the pile load, while the numerical analyses demonstrates a gradual increase in the pile load associated with strain hardening approaching ultimate pile load. It has been discussed that the load-settlement relation mainly depends upon the stiffness of the ground, whilst the shear transfer mechanism depends on shear strength parameters.