• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.25-37
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• 2019

The conventional representative underground cavity restoration methods, which are mainly open-cut methods, require high cost and long period of time for the restoration. Therefore, various trenchless restoration methods have been proposed to improve these disadvantages. The underground cavity restoration method using the expansive material proposed in this paper is one of the trenchless methods. This method fills the underground cavity with high quality backfill soils through the small hole(s) at asphalt layer and compacts backfill soils by insertion of the expansive material within the cavity. In this study, the restoration method using expansive material was constructed in acrylic chamber. The restoration efficiency of the method was analyzed by the fill ratio and degree of relative compaction according to the location and number of bore holes. As a result of the experiment, the restoration efficiency and the optimum construction location were found to be irrelevant.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.377-387
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• 2016

In recent, in case that the underpass is constructed by trenchless method, its stability increases by reinforcing steel pipe with re-bar and mortar after propulsion into the ground to form pipe-roof. Therefore, it can be predicted that the integrated pipe-roof decreases the stress acting on the underpass by sharing load. In this study, to analyze the effect of integrated pipe-roof and behavior of stress around underpass, experimental tests for the rectangular and arch cross section of the underpass are performed using soil chamber. As a result, stress and strain acting on the underpass decrease due to sharing load by integrated pipe-roof. This phenomenon is more pronounced by increasing the stiffness of pipe-roof. Furthermore it can be expected that cross-section of underpass can be economically designed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.469-484
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• 2012

This study aims to numerically investigate ground movement around a square steel pipe as well as a group of square steel pipes induced by its and their ground penetration for trenchless construction of a concrete box. From numerical results, ground movement induced by a square steel pipe is much more dominantly governed by vertical displacement rather than horizontal displacement. Ground settlement induced by pipe penetration is much larger as the overburden becomes lower. The settlement is also shown to be slightly dependent upon the sequence of pipe penetration. More careful construction management is highly in demand during the penetration of upper pipes since their induced settlement occupies approximately 75 percent of total ground settlement after the whole construction of steel pipes.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.97-107
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• 2017

Recently, there have been a lot of incidents related to ground sinks in urban areas, but restoration work is complicated and inconvenience due to on-site control, and particularly, grouting and soil filling are generally applied as recovery measures, but when the grouting or the soil filling is carried out, material segregation phenomenon occurs in the ground or a lot of restoration amount is often required, depending on the state of sinks and the existence of groundwater under the ground and the soil can be lost due to the flow of the ground water, and thus the purpose of this study is to develop a pouch-type filler applied to a trenchless method for emergency reinforcement of the ground sinks with the aim of quick recovery of the ground sink in urban areas, and as a result, it was confirmed that compression strength and the expansion ratio were different according to the temperature of ground water and the compression strength and the expansion ratio could be controlled by mixing alumina powder.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3542-3547
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• 2015

There is commonly used the full depth excavation method of sewer pipeline maintenance in Korea. This induces couple of technical and social problems like increase of construction cost and time for excavation and backfill, increase of public complains and delay of traffic, and so force. In order to overcome these problems, lots of laboratory tests were carried out for sewer pipeline of maintenance materials with trenchless methods. The testing materials are liquid and hardened polyurethane, and polyurethane CIPP. The lab tests were followed by Korean Standard. There are no side effects, like harmless to the human body and air pollution with stink. Judging from the limited test results, all the items tested were satisfied the KS criteria.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.397-419
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• 2012

The pressurizing support tunneling method has been developed that overcomes shortcomings of conventional trenchless methods and applied to the field. The main concept of the new method is the pressurization system which, by means of pressurization bag between outer flange of steel ribs and excavated perimeter, applies higher pressure than the pressure relaxed by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through 3D numerical analyses. The new method was applied to the construction of a 10.7 m wide, 7.9 m high and 85 m long ramp tunnel that passes under ${\bigcirc}{\bigcirc}$ Expressway. By applying the new method, the tunnel construction was successfully completed in 13.5 months which decreases construction time to 35% compared to conventional methods, and ground displacement was almost negligible.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.5
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• pp.513-522
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• 2015

This study is to confirm the effect of pre-installed pipe-roof by measuring earth pressure acting on the underpass. In recently developed trenchless methods pre-inserted steel pipes before ground excavation to form pipe-roof are connected each other with re-bars and filled with mortar. In this study, focusing on the Upgraded Pipe Roof Structure method (UPRS) and Front-Jacking, earth pressure around pipe-roof is measured after insertion of steel pipe to ensure the effect of earth pressure reduction. In case of the UPRS earth pressure is considerably reduced because of the reinforced effect of pipe-roof. In case of the Front-Jacking in which the whole underpass structure is pushed into the ground, earth pressure is not reduced as expected, because the pre-installed pipes are not needed to be reinforced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.677-683
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• 2016

In urban areas, underground tunnel construction sites have spread widely to accommodate rapidly increasing traffic volume along with a high-degree economic growth. Earth tunneling might be adapted frequently for the underground space securing, and various tunneling methods have been developed to stabilize the tunnel face and crown. Among them, the DSM (divided shield method) is gaining popularity for its enhanced stability and construction efficiency. This method has its foundation from the Messer Shield method, which is one of the trenchless special tunneling methods. This study examined the effects of face reinforcement on construction the sequence through a large scale soil chamber test and numerical analyses. The chamber has a size of a 1/2 scale of the real tunnel. Surface settlements were measured according the tunneling process. Commercially available software, MIDAS GTS, was used for numerical analysis and its result was compared with the values obtained from the chamber test. The results of the study show that both settlements of the embanked soils and the stress of the tunnel girder are located within the safe criteria. Overall, this study provides basic data and the potential of using a reinforced tunnel face to enhance DSM applications.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.217-221
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• 2005

도시의 기능이 날로 커져가고 땅속 지하매설물은 포화상태에 이르렀다. 또한 시민들의 의식 수준이 높아가면서 도시에서의 굴착시공은 민원유발과 교통소통장애 문제로 날로 어려워지고 있는 것이 현실이다. KT에서는 무인 및 유인 통신구를 건설할 수 있는 장비를 이미 개발한바 있으며, 본 연구를 통해 도심지에서 보다 효율적으로 통신관로 ${\Phi}50mm,\;{\Phi}150mm,\;{\Phi}300mm$를 시공할 수 있는 장비를 개발하게 되었다. 도시는 복잡하기 때문에 비개착 시공에 있어서 시공 점용면적이 상대적으로 많을 경우 어려움을 겪게된다. 소구경 비개착 장비인 XS-300은 길이 1.45m 폭 0.8m 높이 0.97m 이며 중량은 700kg인 소형장비인 것이 특징이다. XS-300은 도심지에서 통신맨홀 터파기 부분을 압입구로 활용할 수 있으며 경제적인 비용으로 개착식 시공이 불가한 구간에 대한 인입관로 구성과 지하장애물 하월시공, 도로횡단 시공 시에 적합한 장비이다. 특히 타 시설물을 관통한 불량통신시설과 재해에 취약한 통신시설에 대해 안전하고 경제적인 비용으로 이설시공을 할 수 있으며 통신인프라 기초시설 안정화 및 품질고도화에 기여할 수 있을 것이다.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.3
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• pp.211-220
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• 2020

When domestic sewage and rainwater runoff are discharged into a single sewer pipe, it is called a "combined sewer system." The sewage design standards in Korea specify the flow velocity based only on the volume of rainfall; therefore, sedimentation occurs on non-rainy days owing to the reduced flow rate and velocity. This sedimentation reduces the discharge capacity, causes unpleasant odors, and exacerbates the problem of combined sewer overflow concentration. To address this problem, the amount of sewage on non-rainy days, not just the volume of rainfall, should also be considered. There are various theories on sedimentation in sewer movement. This study introduces a self-cleansing velocity based on tractive force theory. By applying a self-cleansing velocity equivalent to the critical shear stress of a sand particle, sedimentation can be reduced on non-rainy days. The amount of sewage changes according to the water use pattern of citizens. The design hourly maximum wastewater flow was considered as a representative value, and the velocity of this flow should be more than the self-cleansing velocity. This design method requires a steeper gradient than existing design criteria. Therefore, the existing sewer pipelines need to be improved and repaired accordingly. In this study, five types of improvement and repair methods that can maximize the use of existing pipelines and minimize the depth of excavation are proposed. The key technologies utilized are trenchless sewer rehabilitation and complex cross-section pipes. Trenchless sewer rehabilitation is a popular sewage repair method. However, it is complex because the cross-section pipes do not have a universal design and require continuous research and development. In an old metropolis with a combined sewer system, it is difficult to carry out excavation work; hence, the methods presented in this study may be useful in the future.