• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3D
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• pp.457-468
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• 2011

Recently, the non-vibration mass excavation method is used on sewage pipes and road construction sites in Jeju. However, a construction cost estimation based on the unit quantity does not provide a proper unit price. In this study, a comparison of the productivity of the standard quantity-per-unit costing method and the one of the work crew combination method was made based on the site monitoring of the non-vibration mass excavation method that is used in construction sites near Jeju. For this, data of 35 sites were collected: a regression equation was derived from the 30 data, and verification was carried out through the remaining 5 data. The analysis concluded that a day's workload is $16.43m^3$. In addition, a combination of the equipment considering the site conditions and the amount of labor, which varies with the number of work crew was obtained in order to estimate the construction cost of the work crew combination method. The construction cost was calculated based on the one-day workload ($16.43m^3$) derived from the regression analysis. The cost then was analyzed and compared with the standard quantity-per-unit costing method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.4
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• pp.499-511
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• 2015

A room-and-pillar underground structure is characterized by its grid-type array of galleries. As a result, its construction and economical efficiency can be governed by excavation sequence of galleries. Therefore, this study aims to study the optimum excavation scheme of a room-and-pillar underground structure by considering its various design factors such as ground conditions and excavation sequences. Drill-and-blast method is assumed as a excavation method for a room-and-pillar underground structure. In addition, two kinds of excavation patterns corresponding to a concurrent and a sequential excavation patterns are considered in this study. For the assumed conditions, the structural stability and the construction efficiency based on the number of faces and the travel distance of a jumbo drilling machine are analyzed for the two excavation patterns. Even though the two kinds of excavation patterns show almost the same structural stability as each other, the concurrent excavation pattern is relatively preferable to the sequential excavation pattern in terms of the number of faces in operation and travel distance of a drilling jumbo.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.197-206
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• 2004

The ground anchor support system may not be occasionally used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in the upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing), is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also, proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear, Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are analyzed. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and the $FLAC^{2D}$ program analysis. And a numerical approach is proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.1-12
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• 2007

For the purpose of effective utilization of domestic second-grown larch as structural members, post and beam construction applying traditional construction to Japanese larch glulam members was adopted with processing by machine pre-cut method. In general, horizontal shear test by KS F 2154 is conducted to assess the horizontal shear properties of the wooden structure by post and beam construction. The frame was consisted of post and beam member with appropriate fasteners, and members have their own processed parts (notch, hole, etc.) that can be well-connected each other. The shear wall was consisted of the frame with screw-nail sheathed panel (OSB). The results of horizontal shear loading tests without vertical loads conducted on the frame and the shear wall structures, the maximum strengths were about 1.9 kN/m and about 9.7 kN/m, the shear rigidities were about 167 kN/rad, 8198 kN/rad, respectively. The strength proportion of the frame specimen was about 20% of the wall's and about 2% in initial stiffness. Nail failures are remarkable on the shear wall specimen with punching shears and shear failures. The shear load factor for the shear wall specimen by the method of Architectural Institute of Japan was 1.5, which was obtained by the bi-linear method. Loading method should be considered to obtain smooth load-deformation relationship. For the better shear performance of the structures, column base and post and beam connections and sheathed panel should be further examined as well.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.87-96
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• 2004

Application of the soil nailing method is continuously extending in maintaining stable excavations and slopes. However, ground anchor support system occasionally may not be used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in an upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing) is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, laboratory model tests are carried out to investigate the failure mechanism and behavior characteristics of the PSN system. Various results of model tests are also analyzed to provide a fundamental basis for the efficient design.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.59-71
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• 2023

Carbon capture, and storage (CCS) is important for the reduction of greenhouse gases and achieving carbon neutrality. CCS focuses on storing captured CO₂ permanently in underground reservoirs. CO₂-enhanced oil recovery (CO₂-EOR) is one form of CCS, where CO₂ is injected into the underground to enhance oil recovery. CO₂-EOR not only aids in the extraction of residual oil but also contributes to carbon neutrality by storing CO₂ underground continuously. CO₂-EOR can be classified into miscible and immiscible methods, with the CO₂-water alternating gas (CO₂-WAG) technique being a representative approach within the miscible method. In CO₂-WAG, water and CO₂ are alternately injected into the reservoir, enabling oil production and CO₂ storage. The WAG method allows for controlling the breakthrough of injection fluids, providing advantages in oil recovery. It also induces hysteresis in relative permeability during the injection and production process, expanding the amount of trapped CO₂. In this study, the effects of enhancing oil recovery and storing CO₂ underground during CO₂-EOR were presented. Additionally, cases of CO₂-EOR application in relation to CCS were introduced.

• 한국도로학회지:도로
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• v.10 no.2
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• pp.58-67
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• 2008

교통량이 많은 도심지내 장대 지하차도 건설은 교통정체 해소에 기여를 하지만 초기 공사비가 많이 소요되는 단점이 있다. 또한, 화재등 유고시 이용자의 안전을 최우선으로 고려되어야 한다. 즉, 장대 지하차도 건설에 있어서 경제성과 안전성이 함께 만족할 수 있는 건설 방안이 필요하다. 세종지하차도는 이러한 문제점을 극복하고자 다음과 같이 지하차도의 환기방식 및 단면, 포장형식, 사고 예방 및 발생시를 대비한 종합방재시스템을 구축하였다. $\cdot$환기방식은 종류식 환기방식의 경제성과 횡류식 환기방식의 제연성능을 겸비할 수 있는 조합형 환기방식과 Duct Arch 단면을 적용하여 공사비 절감 및 운영시 유지관리비를 획기적으로 절감하였다. $\cdot$지하차도 포장형식은 화재시 내화성이 우수하며 유독가스 발생이 없는 HPC(고성능 콘크리트 포장) 포장을 적용하여 이용자의 안전을 최우선으로 고려하였고 일반 아스팔트 포장 및 배수성 아스팔트 포장에 비해 우수한 성능과 공용수명을 가진 공법을 적용함으로서 유지보수비용의 절감을 가능하게 하였다. 또한, 콘크리트포장의 단점인 소음발생을 최소화하기 위해 타이닝과 그루빙을 적용하였다. $\cdot$지하차도내 화재 등 유고시 신속한 대피가 가능하도록 피난 연락문 간격을 167m 간격으로 설치하고 비상탈출계단 6개소를 확보하였다. 또한 노약자 및 환자의 지하차도 외부로 대피를 돕기 위해 비상엘리베이터 3개소를 설치하는 등 사고발생 시 종합적으로 대처할 수 있는 시스템을 마련하여 적용하였다.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.23-29
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• 2014

So far, the grouting using pressure injection has been extensively used to avoid adverse effects such as soil disturbance. Whereas, the pressure injection to the limitations of the diffusion range, so that the kinks would last injection of cement particles by introducing a frequency oscillation effect improved injection method have been recently developed. In this study, a pilot test was performed to compare injection effects of the both methods. The injections using both methods were tested on the embankment which consists of core clay and weathered soil. Subsequently, the injected volume, SPT N values, in-situ permeability and electrical resistivity were measured to compare their effects. The vibration method showed more effective permeation comparing with the pressure method. Also, it showed more homogeneously improved ground than the existing method. For SPT results, the vibration method presented increase of mean N value as much as 17.4 % comparing with the conventional method. Higher electrical resistivity was presented in case of injecting with vibration method and it indicated the injection was extensively completed. Finally, it is expected that the economic feasibility will be improved by decrease of drilling spacing, when the existing method is replaced with vibration method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.61-68
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• 2019

As the pollution of water resources deteriorates due to industrialization and urbanization, it is difficult to supply clean water through a water treatment method using chlorine. Therefore, the introduction of advanced water treatment facilities using ozone is on the increase. However, epoxy which is used as waterproofing and anticorrosives and stainless steel used in conventional waterproofing and anti-corrosive methods have deteriorated because of the strong oxidizing power of ozone, causing problems such as leaking. Moreover, it even causes the durability degradation of a concrete. Therefore, in this study, metal spraying system was used as the means of constructing a metal panel with excellent ozone resistance and chemical resistance which is an easier method than an existing construction method. Ozone resistance was evaluated in accordance with the type of metal sprayed coatings to develop a finishing method which can prevent the concrete structure of water treatment facilities from deterioration. Furthermore, electrochemical stability in actual sewage treatment plant environment was evaluated. Experimental results showed that Ti has superior ozone resistance after spraying and the electrochemical stability in the sewage treatment plant environment showed that Ti has the highest polarization resistance of $403.83k{\cdot}{\Omega}{\cdot}cm^2$, which ensures high levels of durability.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.256-261
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• 2008

The curtain-wall work has been more frequently applied in the construction industry since demand of high-rise buildings has been increased. The curtain-wall work is usually performed with the frame work simultaneously for reducing construction period, but it might be delayed because of several problems caused by interference of process. However, there is not an appropriate tool which can be used by a work manager for adjusting quantity of the construction equipments or the workers when the curtain-wall work was delayed. To resolve this problem a construction simulation anticipating and analyzing potential problems before starting the work can be applied in the curtain wall work. This research suggests a general model for the curtain-wall work by using construction simulation and produces a combination of construction equipments and workers which can estimate optimum work productivity.