• Journal of the Korean Geotechnical Society
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• v.35 no.3
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• pp.5-16
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• 2019

With the recent concentration of urban populations, the constructions of large structures are increasing, along with the development of foundations for large structures. PHC Piles have been used in many structures ever since Japanese introduced the technology at the end of the 20th century. Recently, many studies on the use of the PHC Pile have been carried out as earth retaining using the merits of PHC piles. In this study, static axial compression tests were conducted on the PHC-W piles constructed as column-type in building underground additional wall using the PHC-W earth retaining wall. The end bearing capacity of pile was calculated using the axial load transfer measurement that was obtained from the static axial compression test result. Since end bearing capacity of the PHC-W pile embedded in weathered rock showed a different behaviour from the conventional PHC pile, the calculation method of end bearing capacity for column-type PHC-W piles would be proposed. The unit ultimate end bearing equation proposed for single and group PHC-W pile embedded in weathered rock is $q_b=13.3N_b$ and $q_b=6.8N_b$.

• Journal of the Korean Geosynthetics Society
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• v.7 no.2
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• pp.31-39
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• 2008

The information of cut slope in Baekyang Mt. area, Busan is investigated in order to construct the Slope Management System in Urban Area. The slope inspection sheet is made to record the characteristics for cut slopes, and that is capable to be inputted slope information systematically. The cut slopes in Baekyang Mt. area are consisting of 103 slopes. Most of the cut slopes are constructed in cutting slope and retaining wall (CR). The school is mostly distributed adjacent to cut slopes. The average traverse of cut slopes is approximately 122m, and the average height is approximately 18m. The slopes combined with soil and rock are mostly distributed. The retaining wall was installed in the toe part of cut slope in order to increase the slope stability, and the additional reinforcement methods including the anchor, drainage, preventing rock fall, shotcrete and vegetation were installed in the walls and slopes.

• Tunnel and Underground Space
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• v.10 no.4
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• pp.516-525
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• 2000

Recently, the demand for pollution-free demolition work of old reinforced concrete and steel structure has rapidly increased as the redevelopment of urban area has been accelerated. This study deals with linear shape charges for explosive jet cutting on steel structure. We have tested material and shape of steel structure, characteristics of thickness and strength, shape of linear shape charges, type of shape charges, cumulative charges, type of liner, stand-off distance, detonation method. effect of sound and vibration by air blast in explosive jet cutting method. So, We developed linear shape charges in order to take advantage of optimum explosive jet cutting condition. Shape charges were made of PETN explosives. We obtained the experimental formula to decide the amount of explosive needed for thickness of steel structure plate. There are prospects for application of the explosion curving technology under the open space conditions for dismantling the steel structure and steel bridge, scrapped old boats, which are going out of service.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.387-399
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• 2018

Mine reclamation project is closely related to human's past mining activities and the current human's living environment. It is a reason for the national management. In order to efficiently carry out mine reclamation projects, a precise investigation and analysis of the underground space of the abandoned mine is required. Korea MINE RECLAMATION Corp. is developing a practical technology that is effective in investigating and actually measuring underground cavities. MIRECO EYE system is an exploration equipment for 3D digitization and figuration of underground cavities. As combining a laser, sonar and image acquisition technology, it enables access to information about inaccessible underground cavities and effective management of subsidence risk of mined area. and currently it is also utilized for various purposes in related areas such as investigating urban sinkholes. This article is precise numerical and geometric information analysis obtained through MIRECO EYE system.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1409-1416
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• 2010

It is essential to predict a blasting-induced excavation damage zone (EDZ) beyond the proposed excavation line of a tunnel because the unwanted damage area requires extra support system for tunnel safety. Complicated blasting process which may hinder a proper characterization of the damage zone can be effectively represented by two loading mechanisms. The one is a dynamic impulsive load generating stress waves outwards immediately after detonation. The other is a gas pressure that remains for a relatively long time. Since the gas pressure reopens up the arrested cracks and continues to extend some cracks, it contributes to the final formation of EDZ induced by blasting. This paper presents the simple method to evaluate EDZ induced by gas pressure during blasting in rock. The EDZ is characterized by analyzing crack propagation from the blasthole. To do this, a model of the blasthole with a number of radial cracks of equal length in an infinite elastic plane is considered. In this model, the crack propagation is simulated by using three conditions, the crack propagation criterion, the mass conservation of the gas, and the adiabatic condition. As a result, the stress intensity factor of the crack generally decreases as crack propagates from the blasthole so that the length of the crack is determined. In addition, the effect of rock properties, initial number of cracks, and the adiabatic exponent are investigated.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.327-336
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• 2013

Approximately 70% of the Korean peninsula is composed of mountains, around 99,274 $km^2$. Even worse, population rate of Korea is the No.3 in the world now. Accordingly, it is necessary to develop the potential underground space actively with the concept of another territory to be utilized. The development of underground space should be considered not a choice but an indispensable issue. Since 1970s, many large-scale underground structures have been constructed like as crude-oil storage bins, liquefied petroleum gas storage caverns, and underground pumped storage powerplants. Also, In urban area, the underground facilities such as subway networks, underground shopping mall, underground pedestrian network, electric power tunnels, and car parking lots have been used extensively. The scale of Yeosu oil and gas underground storage facility and Seoul subway systems are one of the massive scale in the world. Recently, the trend of the development of underground space becomes more diverse and larger scale. The current status of Korean underground space developments and strategy are described in this paper.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.1
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• pp.1-14
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• 2018

In this study, we develop and propose damping correction factors for the Korean standard design spectra. The newly proposed Korean standard design spectra has been given only for 5% damping ratio. But in practice, engineers need design spectra for damping values other than 5%. To obtain design spectra for various damping values from the standard spectra, damping correction factors are derived. These factors modify the shape of design spectra in accordance with the damping ratio. Response spectra for various damping values are calculated from the earthquake records that had been used to calculate standard design spectra. They consist of 55 records from 18 earthquakes occurred in overseas intraplate regions and Korea. The regressed spectra for the damping values ranging from 0.5% to 50 % are compared with standard spectra at three regions acceleration, velocity and displacement sensitive regions. The regression analysis of these data rendered formula for damping correction factors. Finally, a single formula for damping correction factors is recommended that is valid for both horizontal and vertical design spectra and that is applicable to the entire range of periods. One thing to note that recommended damping correction factors is valid for the design spectrum of the rock grounds because the design spectra was developed based on the earthquake records of the rock ground.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.87-94
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• 2013

In recent years, tunnel construction is being increased in order to resolve traffic congestion around urban area, however there are a lot of difficulties due to restrictions such as interference with existing alignment, adjacent structures and cost increase of land acquisition as well as public complaints for negative environmental impacts near the expected tunnel construction site. Therefore, applications of close parallel tunnel have been increasing greatly. But close parallel tunnels cannot guarantee the stability compared with normal parallel tunnel which has enough distance between tunnels. So various methods to strengthen the pillar have been introduced recently, however there is few methods which consider the pillar behaviour in the state of compression. In this paper, the reinforcement methods which reflect the behavior of pillar were reviewed with comparision and analysis by numerical method.

• Tunnel and Underground Space
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• v.29 no.1
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• pp.1-11
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• 2019

This study investigated use cases of machine learning technology in domestic medical, manufacturing, finance, automobile, urban sectors and those in overseas mining industry. Through a literature survey, it was found that the machine learning technology has been widely utilized for developing medical image information system, real-time monitoring and fault diagnosis system, security level of information system, autonomous vehicle and integrated city management system. Until now, the use cases have not found in the domestic mining industry, however, several overseas projects have found that introduce the machine learning technology to the mining industry for improving the productivity and safety of mineral exploration or mine development. In the future, the introduction of the machine learning technology to the mining industry is expected to spread gradually.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.7-22
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• 2021

In this study, inverse analysis was performed on the bi-directional axial compressive load test conducted on drilled shafts. And the bearing capacities were analyzed by numerical analysis of various pile tip ground conditions of silt clay, silt sand, sand silt, sand gravel, weathered rock, and soft rock. The bearing capacities were analyzed using the P-S method, the Davisson method, and the allowable sttlement of 25.4 mm. The minimum allowable bearing capacities analyzed by three methods were found to be 19.64 MN ~ 24.96 MN. At this time, the base resistances were sharing a 2% ~ 12% of a head load, shaft resistance were shared 88% ~ 98% of the head load. The greater the strength of pile tip was found to increase the allowable bearing capacity. However, the difference between the maximum allowable bearing capacity and the minimum allowable bearing capacity was 5.32 MN, and the increase in the allowable bearing capacity was only 27% depending on the pile tip.