• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.6
• /
• pp.763-778
• /
• 2019

Abrasive waterjet cutting technology has been used for rock excavation of tunnels and underground structures due to various advantages. In order to cut rocks by using the abrasive waterjet system, abrasive is essential to enhance impact energies for fracturing the target rock. Since garnet abrasives are not produced in Korea, alternative abrasives, instead of garnets, are needed to achieve the economical waterjet cutting. This study is to analyze cutting performance for rocks with sandy particles as alternative abrasive. Cutting tests were carried out on granite specimens at the constant waterjet energy (e.g., water pressure or water flow rate). The five kinds of sands, sampled by construction fields and natural sites, were prepared to perform the experimental tests. When sea sand was used as an alternative abrasive, cutting performance was secured to be 60~70% compared to the commercial garnet abrasive. Thus, it is expected that sand abrasives can be applied on the waterjet cutting process for the economical excavation construction.

• Journal of the Korean Institute of Gas
• /
• v.19 no.4
• /
• pp.62-67
• /
• 2015

In this paper, the consequence analysis has been evaluated for the damage effects of the LPG storage tanks when they are installed on the ground or underground. They should be performed to identify measures to reduce risks for the LPG storage tanks which are more widely used. In order to conduct a damage effect evaluation of the LPG storage tanks installed underground, FDS was used to simulate the LPG storage tanks installed and housed within a facility. The maximum pressure of the storage facilities for the LPG storage tanks has been calculated from the FDS, and it's results are used as an input variable for Phast which is a commercial software for evaluating the damage effects. Getting results from the consequence analysis and computational simulations(diffusion range of LFL and UFL, jet fire or explosions) were quantitatively presented for the damage effects.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.7
• /
• pp.1623-1629
• /
• 2015

By increasing due to large-scale residential and commercial apartments or factories or were, and increases the length of the cable is connected from the electrical room, the thickness of the cable, the trend is also being gradually thicker to increase the power consumption. In this paper, the programs install the cable inserted in the rope a double bonded brake pipe to be laid underground in these cables, and to reliably collect various kinds of data such as a tension at the time of laying the cable, the distance and speed design, and the sample data was acquired through hardware making them. Through this, it was confirmed that, worker was significantly reduced and work time was shortened to the traditional mechanical laying equipment. And to obtain a performance of improving the reliability of operation, because the use of the working data to the management and evaluation.

• Tunnel and Underground Space
• /
• v.15 no.3 s.56
• /
• pp.169-176
• /
• 2005

The decreasing pattern of underground temperature measured at 'Gonjiam cold storage cavern' during 7 years which was the first commercial scale underground food storage cavern in Korea was analyzed. The variation of energy consumption was discussed by comparing the consumed energy at the initial operation stage with that at later stage, when the temperature distribution reached a stabilized condition. The point to be considered at the design stage was also discussed by comparing the required refrigerator capacity at the initial operation stage with that at later stage. The extra energy to freeze the groundwater contained in pore space was discussed by analyzing the changing pattern of the rock temperature. The variation of measured rock temperature was compared with the estimated temperature using a numerical code, FLAC. The accuracy of the numerical estimation was discussed by comparing the heat flux measured by the operation time of the refrigerator with that estimated numerically.

• Membrane and Water Treatment
• /
• v.10 no.1
• /
• pp.75-82
• /
• 2019

In a highly urbanized area, land availability is limited for the installation of space consuming stormwater systems for best management practices (BMPs), leading to the consideration of underground stormwater treatment devices connected to the stormwater pipe system. The configuration of a stormwater pipe network determines the hydrological and pollutant transport characteristics of the stormwater discharged through the pipe network, and thus should be an important design consideration for effective management of stormwater quantity and quality. This article presents a multi-objective optimization approach for designing a stormwater pipe network with on-line stormwater treatment devices to achieve an optimal trade-off between the total installation cost and the annual removal efficiency of total suspended solids (TSS). The Non-dominated Sorted Genetic Algorithm-II (NSGA-II) was adapted to solve the multi-objective optimization problem. The study site used to demonstrate the developed approach was a commercial area that has an existing pipe network with eight outfalls into an adjacent stream in Yongin City, South Korea. The stormwater management model (SWMM) was calibrated based on the data obtained from a subcatchment within the study area and was further used to simulate the flow rates and TSS discharge rates through a given pipe network for the entire study area. In the simulation, an underground stormwater treatment device was assumed to be installed at each outfall and sized proportional to the average flow rate at the outfall. The total installation cost for the pipes and underground devices was estimated based on empirical formulas using the flow rates and TSS discharge rates simulated by the SWMM. In the demonstration example, the installation cost could be reduced by up to 9% while the annual TSS removal efficiency could be increased by 4% compared to the original pipe network configuration. The annual TSS removal efficiency was relatively insensitive to the total installation cost in the Pareto-optimal solutions of the pipe network design. The results suggested that the installation cost of the pipes and stormwater treatment devices can be substantially reduced without significantly compromising the pollutant removal efficiency when the pipe network is optimally designed.

• Journal of the Korean Institute of Gas
• /
• v.16 no.2
• /
• pp.1-8
• /
• 2012

According to the last 5 year statistics of KGS, there occurred 22 under ground gas pipe accidents per year in Korea. And about 5 accidents per year were caused from the third party digging. IT recognition technique could reduce such underground gas accidents. Among IT recognition technique, RFID is most poplar. In the air, RFID were applied to various fields including the distribution industry, but underground condition, the research and application cases of RFID were little This research was undertaken to see the applicability of RFID to underground gas pipe safety. By use of 900 MHz RFID reader and commercial metal tag, the stable recognition distance was measured in the similar underground condition of LNG pipe. Stable recognition depth of RFID tag were measured to be 50, 45, 25 cm in the medium of soil, 5 cm-thick-concrete+soil, and water respectively. The measured distances were considered to be the meaningful distance to prevent the gas pipe accidents Also the efficient ways to input the required gas pipe data to the 24 byte metal tag were proposed. Application of RFID to underground LNG supply system will not only reduce the gas accidents due to third party digging but also improve the gas line maintenance efficiency.

• Journal of Environmental Health Sciences
• /
• v.27 no.2
• /
• pp.1-9
• /
• 2001

This study was carried out to investigate the microbial characteristics of the urban air pollution in the subway stations, streets, department stores, wholesale markets, underground shopping centers, buildings, parks, houses and apartments in the Seoul and the suburbs area. Total cell count, total mold count and the presence of opportunistic pathogens(Streptococcus pneumoniae, Klebsiella pneumoniae, Aspergillus spp., Penicillium spp.) were evaluated determine the microbial air quality. Total cell count and mold count of indoor air in the houses and apartments were 2.9$\times$10$^2$-6.3$\times$10$^2$cfu/㎥ and 60-1.8$\times$10$^2$cfu/㎥, respectively, and the department stores and wholesale markets had much lower cell count than the houses and apartments. Ground level of commercial stations were 2.6 fold higher than the general subway stations, and Apergillus spp. and Penicillium spp. which could cause the bronchus and lung diseases were detected 17 sampling site out of 45. Dust were collected from the commercial facilities and houses, and total cell and mold count of the dust were 4.3$\times$10$^3$-1.7$\times$10$^{6}$ cfu/g and 2.3$\times$10$^3$-6.5 $\times$10$^4$cfu/g, respectively. Therefore the dust might be one of the main reservoir of microorganims.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.5 no.2
• /
• pp.137-146
• /
• 1995

Twenty(20) large commercial buildings located in Seoul with friable sprayed-on surface insulation material on ceilings were investigated for asbestos content in bulk material by polarized light microscopy and for airborne fiber concentrations in buildings by phase contrast microscopy. In addition, such building-related variables as building age, numbers of traffic, airflow, surface conditions of the ceiling, temperature, and humidity were studied for any correlation with airborne fiber concentrations. The results were as follows: 1. Chrysotile asbestos was found in two bulk samples with 3-5% content and with <1%in one sample out of total 20 bulk samples collected. Glass fiber and mineral wool were the two major constituents of the bulk samples. 2. The ceiling surfaces were very friable in 16 buildings and were relatively hard in 4 buildings. The friability of the surface material was dependent upon the type and the amount of binder that had been mixed with the sprayed-on surface material. 3. Airborne fiber concentrations were log-normally distributed and the geometric mean(geometric standard deviation) fiber concentrations in the underground parking lots, inside buildings, and outdoor ambient air were 0.0063(1.97)f/cc, 0.0068(2.29)f/cc, and 0.0033(2.36)f/cc, respectively. 4. No significant relationship of airborne fiber concentrations and all building-related variables studied except humidity was found. The results of this study suggest that the sprayed-on surface insulation material found in some commercial buildings may possibly be contaminated with asbestos. Since most of the ceiling surfaces surveyed were very friable and poorly maintained and the airborne fiber concentrations were relatively high, there is a possibility of asbestos fiber contamination in these buildings, particularly at those buildings with asbestos-contaminated surface material. Since poorly maintained surface conditions were thought to be a source of high airborne fiber concentrations, there is a urgent need of a systematic operation and maintenance program. Further study of non-occupational asbestos exposure in general population utilizing advanced analytical technique such as transmission electron microscopy is highly recommended.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.652-659
• /
• 2011

Due to overuse of commercial network systems such as bluetooth and WI-FI, the problems of frequency interruption and line-crossing may arise. For this reason, wireless communication frequency ISM 2.4GHz, a recently adapted concept in Korea which is employeed by RF-CBTC system, is predicted not to have guarantee for outstanding and continuous performance. Therefore in this study, considering these problems, 5GHz capacity wireless Lans with international standard 802.11a/b/g applied were installed in the underground urban transit areas and it was proved that these lans exceeded the performance level of 2.4GHz with international standard 802.11b which is being introduced in the nation. In addition, it was verified through carrying out an application test that the communication condition was stable in a running train with high speed in the tunnel.

• Journal of Korean Association for Spatial Structures
• /
• v.14 no.1
• /
• pp.69-76
• /
• 2014

When we excavate an underground to build basement, the ground anchors are needed to prevent collapse of neighboring ground, subsidence and movement. Ground anchor construction required shore sheet piles, wales and struts as to maintain secure excavation. Existing box-type bracket using head part of ground anchor can not be possibly adjustable to the boring angle because the brackets are manufactured with unified angle in a factory. Also, box-type brackets have imperfection and instability caused by inequable force. In this study, a new bracket system is proposed. The bracket's side plate is reinforced and the angle of boring can be controlled. To investigate the structural performance of presented brackets, FEM analysis has been performed by using ANSYS commercial program. As a result, this bracket shows sufficient stability for all angle case and the strength is increased about 24% than existing bracket.