• Title/Summary/Keyword: 철도건설공사

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소단면 터널에서 에멀젼폭약의 사압현상과 대책

  • Min, Hyeong-Dong;Jeong, Min-Su;Jin, Yeon-Ho;Park, Yun-Seok
    • Proceedings of the KSEE Conference
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    • 2008.10a
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    • pp.17-28
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    • 2008
  • 국책사업이나 SOC의 확충을 위한 도로 및 철도의 건설에서 적용되는 터널의 단면크기를 보면, $50m^2$에서부터 $100m^2$이상의 중 대단면 터널이 주를 이루고 있으나, 전력구, 통신구, 소규모로 운영되는 광산의 채광용 터널, 용수를 위한 도수로터널 등 특수한 용도로 설계, 시공되고 있는 터널에서는 $20m^2$이하의 단면크기를 갖는 경우가 있다. 이러한 소단면 터널의 경우에는 협소한 작업공간으로 인하여 적용공법 뿐만 아니라 장비의 사용 또한 제약을 받게 되어 작업효율이 저하되고 공사기간이 늘어나게 되는 등 여러 가지 문제점을 안고 있다. 특히, 에멀젼 폭약을 사용하는 발파에서 먼저 기폭된 발파공의 충격압력에 의해 인접공의 폭약이 예비압축(Precompression)되어 사압현상을 일으키고 잔류약을 발생시키는 사례가 종종 발생하고 있다. 사압현상은 당해 발파의 실패와 함께 2차적인 사고의 위험요인이 될 수 있으므로 이를 방지하기 위한 대책을 수립하여야 한다. 이를 위해 기존 문헌을 통하여 사압현상의 원인과 발생 가능성을 검토하였고, 국내에서 주로 사용되는 에멀전폭약의 수중 내충격성시험과 충격압력 전달시험을 실시하여 사압현상의 발생정도를 측정하였으며, 사압현상이 발생한 소단면 터널현장을 대상으로 대책을 수립하여 적용하였다. 심발방법을 변경하여 전단의 충격압력을 견딜 수 있는 공간격을 확보하고 뇌관의 초시간격을 적절하게 배치한 발파패턴을 적용한결과, 사압현상을 억제하고 잔류약의 발생을 감소시켜 계획 굴진장을 확보하고 파쇄석의 크기를 감소시키는 등 양호한 결과를 얻을 수 있었다.

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Relationship Between Net Penetration Rate and Thrust of Shielded TBM in Hard Rock (암반층에서 Shield TBM의 굴착속도와 추력과의 관계)

  • Park, Chul-Hwan;Park, Chan;Jeon, Yang-Soo;Park, Yeon-Jun
    • Tunnel and Underground Space
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    • v.12 no.2
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    • pp.115-119
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    • 2002
  • Four tunnels have been planned to operate a large diameter shielded TBM in Gwangju urban subway construction site. No.1 tunnel has completely been excavated for 13 months operating. Net penetration rate and its relations with thrust farce of the shielded TBM are analysis in this report. This shallow depth tunnel of 536m length is located in soil layers at launching and in hard rocks at ending with 84 m length. The weekly net penetration rates haute dropped down as low as 20∼110 mm/hr in rock while 400∼800 mm/hr in soil. The actual penetration rates we proved to be high as the theoretical penetration rate which is analysis in consideration of conditions of machine and rock. And net penetration rate is investigated to increase linearly thrust force.

Risk analysis for sidetrack construction during subway tunnel operation (기존 지하철 터널 운영 중 대피선 건설 시공 리스크 분석)

  • Jun, Jonghun;Chung, Heeyoung;Koh, Sung-Yil;Yoon, Hee Taek;Yi, Na Hyun;Choi, Hangseok
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.4
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    • pp.401-417
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    • 2020
  • As an increasing demand for rapid railway transportation, the construction of sidetrack is inevitable to operate local and express trains simultaneously. However, the current technologies for the sidetrack construction method require a long construction period by interrupting the operation of the existing subway line, as well as cause a huge economic loss. Thus, it is necessary to study the sidetrack construction method under the special situation that the subway is in operation and to analyze the risk of the existing tunnel enlargement process for the sidetrack construction. Therefore, in this paper, the Government Complex Gwacheon station on Subway Line 4 was considered as a target station for the virtual sidetrack construction and the optimal sidetrack construction plan was derived. Subsequently, the application of risk management process was carried out in the order of identifying risk, risk response planning, performing a risk analysis, risk monitoring and control for potential risk events during the construction of sidetrack under the subway operation. A total of eight potential risk events and risk mitigation methods were selected, and a risk assessment matrix was established using the five-step risk probability and impact level criteria to perform the risk assessment including residual risks. Based on the results of the risk assessment, the risk grade and the reduction effect of each risk mitigation method were confirmed.

Safety Evaluation Method for Ground Ammunition and Explosive Storage Facilities due to Underground Tunnel Blast (지하시설 굴착공사에 따른 탄약저장시설 안전성 평가방법 연구)

  • Park, Sangwoo;Kim, Kuk-Joo;Park, Young-Jun
    • Journal of the Korea Institute of Building Construction
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    • v.19 no.4
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    • pp.331-339
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    • 2019
  • Recently, expansion of urban and social infrastructures is planned to go through the transfer of military facilities or crossing the infrastructures via underground tunnels. However, when crossing facilities such as ammunition and explosive storages, a high level of safety assessment is required to prevent an accidental explosion of ground ammunition. In this study, a case study was conducted to evaluate the effect of blasting for the construction of tunnel on the ground ammunition facilities. The design section of Sinansan train operated by the Korea Railroad Authority with agreement of the Ministry of National Defense was selected. For the purpose of this study, the vibration velocity due to explosion was predicted by using GTS-NX, a numerical analysis program. Through literature review, it was confirmed that the vibration velocity of 0.2cm/sec can be a safety evaluation standard. These safety evaluation indicators and procedures used in this study can be utilized as an index of safety evaluation in the planning of social infrastructures that cross the ammunition facilities in the future.

A Study on Evaluation Method of Cable Tension for Railway Steel Composite Bridge (강철도 복합교량 케이블의 장력 평가기법에 관한 연구)

  • Choi, Jung-Youl;Lee, Soo-Jae;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
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    • v.8 no.4
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    • pp.407-413
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    • 2022
  • In this study, the empirical formula for evaluating cable tension based on long-term measurement for about 3 years according to temperature change was proposed by proving the correlation between the expansion joint displacement of the upper road bridge and the cable tension of the lower railway bridge. The tension prediction results using the empirical formula for tension evaluation each cables proposed in this study were found to be in good agreement with the cable tension using the vibration method within 3%. Therefore, it was analyzed that it could be applied together with the vibration method that was an experimental technique, to predict and evaluate the cable tension in serviced railway steel composite bridge. As a result of applying the estimated temperature calculated by the empirical formula for expansion proposed in this study to the empirical formula, it was analyzed that a high level of reliability could be secured when compared with the vibration method. Therefore, it is judged that the empirical formula for cable tension evaluation reflecting the estimated temperature proposed in this study can be used to predict the tension of cables according to climate change in the future and establish a maintenance plan.

A Study on Estimation Method of Concrete Sleeper Strength for Sleeper Floating Track using Rebound Hardness Test Method (반발경도법을 이용한 침목플로팅 궤도의 콘크리트 침목 강도추정 기법 연구)

  • Chung, Jee-Seung;Lee, Jeong-Sug;Choi, Jung-Youl
    • The Journal of the Convergence on Culture Technology
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    • v.8 no.3
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    • pp.277-282
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    • 2022
  • The sleeper floating track (STEDEF) in this study was a track type in which a very soft resilience pad was installed under a relatively thin concrete sleeper (RC Block). Therefore it was expected that the resilience pad could affect the estimation results of the concrete strength. In this study, field applicability evaluation was performed to apply the rebound hardness test method, which was a general method for estimating the compressive strength of concrete in civil structures, to concrete sleepers of railway tracks. In order to analyze the strength estimation technique of concrete sleepers reflecting the characteristics of track structures different from those of civil structures, the parameter experiments that could affect the strength estimation results of concrete sleepers in a serviced line were performed. As a result of the study, the appropriate hitting position was suggested considering the shape of the concrete sleeper, and the difference in strength estimation results according to the condition of the concrete sleeper and supporting conditions was derived.

Development of design charts for concrete lining in a circular shaft (원형수직구 콘크리트라이닝 단면설계도표 개발)

  • Shin, Young-Wan;Kim, Sung-Soo;Kim, Young-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.2
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    • pp.165-175
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    • 2010
  • Recently, requirement of a long subsea tunnel has increased due to political, economical and social demands such as saving of distribution costs, improvement of traffic convenience, and regional development. Road and railroad tunnel need a shaft for construction and ventilation because of increase of tunnel length. Shaft diameter, lining sectional thickness and rebar quantity have to be determined for design of concrete lining in the shaft. A lot of structural analyses are needed for optimal design of concrete lining considering shaft diameter, load conditions and ground conditions. Design charts are proposed by structural analyses for various conditions in this study. A sectional thickness and rebar quantity can be easily determined using the proposed design charts.

A Study on Relationship between Structural Safety and Maintenance of Derailing Prevent Guard Rail (탈선방지 가드레일의 구조안전성과 유지보수 상관성에 관한 연구)

  • Jung-Youl Choi;Hyeon-Yo Park;Jee-Seung Chung
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.4
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    • pp.593-599
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    • 2023
  • There is risk of derailment due to various factors such as vehicle-track load imbalance in curved parts, so urban railways install and operate derailing prevent guard rails. The angle-type derailing prevent guard rail is composed of various parts including the guard angle. Even if derailment does not occur, various damages occur in the components, so continuous maintenance is required. Through the damage status analysis, the components of the angle-type derailing prevent guard rail with high damage frequency were classified, and conditions for the occurrence of various damages were investigated. In addition, a numerical analysis using a precise 3D numerical model was performed to analyze the cause of the damage analytically. In order to analytically simulate the derailment situation, the static ultimate load condition was applied, and the actual drawing of the angle-type derailing prevent guard rails, rails, and wheels was used for modeling. By analyzing the results of the damage status investigation and finite element analysis, we tried to investigate the damage of the components.

Study on the Occurrence of Tunnel Damage when a Large-scale Fault Zone Exists at the Top and Bottom of a Tunnel (대규모 단층대가 터널 상하부에 존재하는 조건에서 터널 변상 사례 연구)

  • Jeongyong Lee;Seungho Lee;Nagyoung Kim
    • Journal of the Korean GEO-environmental Society
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    • v.24 no.12
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    • pp.53-60
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    • 2023
  • Recently, along with the improvement of high-speed rail and road design speed, the proportion of tunnel construction work is increasing proportionally. In particular, the construction of long tunnels is rapidly increasing due to the mountainous terrain of our country. In this way, due to the trend of tunnels becoming longer, it is difficult to design and construct tunnels by avoiding fault zones. In the case of tunnel construction in mountainous areas, ground investigation is often difficult even during design due to the topographical conditions, making precise ground investigation difficult, and as a result, the upper part of the tunnel is damaged during tunnel construction. When fault zones, which are vulnerable to weathering, exist, the stability of the tunnel during excavation is directly affected by the fault zone distribution, strength characteristics, and groundwater distribution range. In particular, when a fault zone is distributed in the upper part of a tunnel, damage such as tunnel collapse and excessive displacement may occur, and in order to prevent this in advance, countermeasures must be established through analysis of similar cases. Therefore, in this study, when a large-scale fault zone exists in the upper part of a tunnel, the relationship and characteristics of damage to the tunnel structure were analyzed.

Natural Frequency Measurement for Scour Damage Assessment of Caisson Pier (교량 우물통 기초의 세굴피해 평가를 위한 고유진동수 측정)

  • Nguyen, Quang-Thien-Buu;Ko, Seok-Jun;Jung, Gyungja;Lee, Ju-Hyung;Yoo, Min-Taek;Kim, Sung-Ryul
    • Journal of the Korean Geotechnical Society
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    • v.37 no.11
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    • pp.51-60
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    • 2021
  • River scour erodes the soil around the pier, reducing the lateral bearing capacity of the pier and lowering the stability of the structure. In this study, in order to examine the effect of scouring on the stability of the structure, an experiment was performed to measure the natural frequency of the pier according to the excavation of the surrounding ground. Impact vibration test was conducted on the pier with the caisson foundation of the Mangyeonggang Bridge, which is scheduled to be demolished. Accelerometers were attached to the top, center, and bottom of the pier and the acceleration responses were measured by hitting those three points. The experimental results showed that the top hit showed consistent and reasonable results of the acceleration responses according to the hitting position. The measured accelerations were converted to the frequency domain through Fast Fourier Transform (FFT), and then the natural frequency was determined. In addition, to analyze the scour effect on the natural frequency of the pier, the ground around the pier was excavated and the natural frequency change was analyzed. As a result, the natural frequency showed the decreasing tendency according to the excavation depth, but the decrease was small due to the large stiffness of the caisson foundation.