• Title/Summary/Keyword: 소단면 터널

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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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    • 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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Dead Pressure and its measures of Emulsion Explosives at Small Sectional Tunnel (소단면 터널에서 에멀젼폭약의 사압현상과 대책)

  • Min, Hyung-Dong;Jeong, Min-Su;Jin, Yeon-Ho;Park, Yun-Suk
    • Explosives and Blasting
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    • v.26 no.2
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    • pp.29-37
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    • 2008
  • In general, the size of tunnel cross section in construction site is $50{\sim}200m^2$. But, electric cable tunnel, telecommunication cable tunnel, mine tunnel. Waterproof tunnel have small cross section less than $20m^2$. There are so many problem at small sectional tunnel: restriction of equipment, dead pressure by precompression, loss of efficiency, increase of work time. Especially, explosives remainder by precompression of previous detonation is serious problem. To find its measures of dead pressure (explosives remainder), the following series of progress have been conducted: (1) survey of previous study (2) investigate causes of dead pressure (3) set up of its measures (4) application and appraisal at tunnel site. The measures, change of cut pattern, hole space over 40cm, adjustment of delay time, are proved by experimental results.

An analytical study on the fire characteristics of the small tunnel with large smoke exhaust port (대배기구 배연방식을 적용한 소형차 전용 터널의 화재특성에 관한 해석적 연구)

  • Yoo, Ji-Oh;Kim, Jin-Su;Rhee, Kwan-Seok
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.3
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    • pp.375-388
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    • 2017
  • In order to solve the traffic congest and environmental issues, small-cross section tunnel for small car only is increasing, but there is not standard for installation of disaster prevention facility. In this study, in order to investigate the behavioral characteristics of thermal environment and smoke in a small cross section tunnels with a large port exhaust ventilation system, the A86, the U-Smartway and the Seobu moterawy tunnel, Temperature and CO concentration in case of fire according to cross sectional area, heat release rate and exhaust air flow rate were analyzed by numerical analysis and the results were as follows. As the cross-sectional area of the tunnel decreases, the temperature of the fire zone increases and the rate of temperature rise is not significantly affected by heat release rate. However, there is a difference depending on the change of the exhaust air flow rate. In the case of applying the exhaust air flow rate $Q_3+2.5Ar$ of the large port exhaust ventilation system, the temperature of the fire zone was 7.1 times for A86 ($Ar=25.3m^2$) and 5.4 time for U-smartway ($Ar=37.32m^2$) by Seobu moterway tunnel ($Ar=46.67m^2$). The CO concentration of fire zone also showed the same tendency. The A86 tunnels were 10.7 times and the U-Smartways were 9.5 times more than the Seobu moterway. Therefore, in the case of a small section tunnel, the thermal environment and noxious gas concentration due to the reduction of the cross-sectional area are expected to increase significantly more than the cross-sectional reduction rate.

A Study on Effective Blasting Patterns on Small Area Tunnel (소단면 터널에서 효율적인 발파 패턴에 관한 연구)

  • Lim, Han-Uk;Kwon, O-Sung
    • Journal of Industrial Technology
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    • v.26 no.A
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    • pp.17-28
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    • 2006
  • In underground drilling and blasting, particularly in small headings(generally under $20m^2$), the prospects for changes of blast parameters are usually more limited than those employed by large area tunnel(over $20m^2$). It is also well known that the consumption of explosives and specific drilling rate for small tunnel areas are exponentially increased also tunnel areas decrease. To confirm above results, some tests for two tunnels(irrigation water tunnel with $6.0m^2$ area, electric supplies tunnel with $15.0m^2$) are also carried out in this study. As a results, specific drilling rate and specific charge for irrigation water tunnel were decreased from 13.8 to $7.7m/m^3$ and from 4.88 to $2.56kg/m^3$ respectively. Those for electric supplies tunnel were also decreased from 8.0 to $4.9m/m^3$ and from 3.46 to $2.22kg/m^3$.

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Study on key safety hazards and risk assessments for small section utility tunnel in urban areas (도심지 소단면 터널식 공동구의 핵심 안전 위험요소 및 위험성 평가 연구)

  • Seong, Joo-Hyun;Jung, Min-Hyung
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.6
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    • pp.931-946
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    • 2018
  • In line with the increased usability of utility pipe conduits in urban areas, construction and R&D activities of utility tunnel, incorporated with the shield TBM method, are actively under way. The utility tunnels are installed through underground excavation, and thus are relatively weak in terms of construction safety. However, hazards associated with the utility tunnel construction have not been properly identified, despite the introduction of a policy to the 'Design for Safety' for the purpose of reducing accident rates in the construction industry. Therefore, in this study, following the derivation of hazards associated with utility tunnel, these hazards were then used as the basis to uncover key safety hazards requiring extensive management in a field, which were then used to conduct a risk assessment having applied the matrix method so that the results can be utilized in risk assessment during the stages of utility tunnel planning, design, and construction, while also serving as a data reference.

Effects of interface stiffness on dynamic behavior of connections between vertical shafts and tunnels under earthquake (지진 시 공동구용 수직구-터널 접속부 거동에 대한 경계면 강성 계수의 영향)

  • Kim, Jung-Tae;Hong, Eun-Soo;Kang, Seok-Jun;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.6
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    • pp.861-874
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    • 2019
  • A great interest in the seismic performance evaluation of small size tunnel structures such as utility tunnel has been taken since recent earthquakes at Pohang and Gyeongju in Korea. In this study, the three-dimensional dynamic analyses of vertical shaft and horizontal tunnel under seismic load were carried out using FLAC3D. Especially, parametric analyses was performed to investigate the effects of interfacial stiffness on interfacial behavior between soil and structure. The parametric analysis showed that the interfacial stiffness scarcely gave an effect on the global dynamic behavior of the structure, while had a significant effect on the local displacement behavior of the connections. The magnitude of the interfacial stiffness was inversely proportional to the displacement, while the magnitude of interface stiffness was proportional to the normal and shear stresses. The results of this study suggest the limitations of the existing empirical equations for interfacial stiffness and emphasize the need to develop new interfacial stiffness models.

A study on the operation characteristics of oversized exhaust port applicable to double-deck tunnel (복층터널에 적용 가능한 화재 연동형 대배기구 운영 특성 분석 연구)

  • Park, Jinouk;Yoo, Yongho;Kim, Yangkyun;Park, Byoungjik;Kim, Whiseong
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.6
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    • pp.887-895
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    • 2019
  • Recently, the number of underground road development projects has been increasing to solve traffic problems in the national capital region and metropolitan areas with intensified overcrowding, and there has been a tendency to plan underground roads by applying a double-deck tunnel technology that has advantages in constructability and economical efficiency. The double-deck tunnel has a structure where one excavation section is divided into two parts and used as up and down lines, and is mainly used as a road for small vehicles only due to its low floor height. In addition, due to the small cross-sectional area, it has characteristics different from those of general road tunnels in terms of ventilation and disaster prevention. In this regard, this study proposed an operational plan that applies an oversized exhaust system, which is one of semi-transverse ventilation systems, to small cross-sectional tunnels like double-deck tunnel with low floor height, and a comparative analysis between smoke exhaust characteristics according to the fire occurrence locations and oversized exhaust systems was conducted using the Fire Dynamics Simulator (FDS). The results showed that unlike uniform exhaust, intensive smoke exhaust using the oversized exhaust port maximized the delay effect of smoke diffusion and limited the smoke within 50 m above and below the fire point.

A study on the optimal reinforced zone of a small sectional shield TBM tunnel in difficult ground (특수지반 구간의 소단면 쉴드 TBM 터널 굴착 시 최적 보강영역 연구)

  • Kang, Byung-Yun;Park, Hyung-Keun;Cha, Jae-Hoon;Kim, Young-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.6
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    • pp.735-747
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    • 2019
  • Due to the lack of ground space by urbanization, the demand of utility tunnels for laying social facilities is increasing. During the construction of a utility tunnel in downtown area using a shield TBM, various problems may occur when difficult ground is encountered such as mixed ground and cobbly ground. Thus, in this study, using MIDAS GTS NX (Ver. 280), a numerical analysis was performed on characteristics of difficult ground, reinforced area, depth of cover and groundwater level to analyze the optimal ground reinforced area according to combination of parameters. As a result, it was difficult to secure stability in unconstrained excavation cases on both the mixed ground and the cobbly ground. However, when ground reinforcement grouting as much as 2.0D is applied, convergence occurred within the allowable limit, except for mixed ground with a depth of cover 30 m. In addition, excessive leakage occurred during excavation of both the mixed ground and the cobbly layers. It was able to secure stability after applying waterproof grouting.

A study on the optimal reinforcement area for excavation of a small cross-section shield TBM tunnel in fault fracture zone through parameter analysis (매개변수 분석을 통한 단층파쇄대의 소단면 쉴드 TBM 터널 굴착 시 최적 보강영역 연구)

  • Kang, Byung-Yun;Park, Hyung Keun;Cha, Jae-Hoon;Kim, Young-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.3
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    • pp.261-275
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    • 2020
  • When excavating a small cross-section tunnel in a fault fracture zone using the shield TBM method, there is a high possibility of excessive convergence and collapse. Appropriate ground reinforcement is required to minimize construction cost loss and trouble due to a fault fracture zone. In this study, the optimal reinforcement area was suggested and the surrounding ground behavior was investigated through numerical analysis using MIDAS GTS NX (Ver. 280). For the parameters, the width of the fault fracture zone, the existence of fault gouge, and the groundwater level and depth of cover were applied. As a result, when there is not fault gouge, the convergence and ground settlement are satisfied the standard when applying ground reinforcement by up to 0.5D. And, due to the high permeability coefficient, it is judged that it is necessary to apply 0.5D reinforcement. There is a fault gouge, it was possible to secure stability when applying ground reinforcement between the entire fault fracture zone from the top of the tunnel to 0.5D. And, because the groundwater discharge occurred within the standard value due to the fault gouge, reinforcement was unnecessary.

A study on the fire characteristics according to the installation type of large smoke exhaust port in a small cross sectional tunnel fire (소단면 대심도 터널 화재시 대배기구의 설치형태에 따른 화재특성 연구)

  • Choi, Pan-Gyu;Baek, Doo-San;Yoo, Ji-Oh;Kim, Chang-Yong
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.1
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    • pp.201-210
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    • 2019
  • Recently, due to the efforts to mitigate traffic congestion and expansion of space efficiency, the construction of underground roads has been increased in big-scale cities. Since tunnels in the city have a higher chance for a fire leading to a great tragedy during a severe traffic jam than mountain tunnels, it is highly likely that it will be constructed as a tunnel, having a small cross section, for small vehicles. However, if they are constructed as such small-vehicle tunnels, it would be possible to reduce the design fire intensity while the concentration of harmful gases would increase due to a reduction in the small cross sectional area, led by a decrease in the tunnel height. In this study, behaviors of fire smoke by the installation interval and format of large-scale exhaust-gas ports were examined and compared in the analysis of temperatures and CO concentrations of a tunnel and its results were as the following. Although there were no significant differences in the smoke spreading distance between installation intervals, but in this study, 100 m was found to be the most effective installation interval. The smoke exhaustion performance was found to be excellent in the order of $4m{\times}3m$, $6m{\times}2m$, and $3m{\times}2m$ (2 lane) of the smoke spreading distance. Although there was no significant difference in the smoke spreading distance between formats of large-scale exhaust-gas ports, it was found that the smoke spreading distance was larger than other cases when it was $3m{\times}2m$ in the fire growing process. The analysis of smoke spreading distances by the aspect ratio showed that a smoke spreading distance was shorted when its the smoke spreading distance was found to be shorter when its traverse distance was relatively longer than its longitudinal distance.