• Title/Summary/Keyword: Underground Works

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Hydrogeological Stability Study on the Underground Oil Storage Caverns by Numerical Modeling (수치모델링을 이용한 지하원유비축시설의 수리지질학적 안정성 연구)

  • 김경수;정지곤
    • The Journal of Engineering Geology
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    • v.12 no.1
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    • pp.35-51
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    • 2002
  • This study aims to establish the methodology for design of an optimum water curtain system of the unlined underground oil storage cavern satisfying the requirements of hydrodynamic performance in a volcanic terrain of the south coastal area. For the optimum water curtain system in the storage facility, the general characteristics of groundwater flow system in the site are quantitatively described, i.e. distribution of hydraulic gradients, groundwater inflow rate into the storage caverns, and hydrogeologic influence area of the cavern. In this study, numerical models such as MODFLOW, FracMan/MAFIC and CONNECTFLOW are used for calculating the hydrogeological stability parameters. The design of a horizontal water curtain system requires considering the distance between water curtain and storage cavern, spacing of the water curtain boreholes, and injection pressure. From the numerical simulations at different scales, the optimum water curtain systems satisfying the containment criteria are obtained. The inflow rates into storage caverns estimated by a continuum model ranged from about 120 m$^3$/day during the operation stage to 130~140m$^3$/day during the construction stage, whereas the inflow rates by a fracture network model are 80~175m$^3$/day. The excavation works in the site will generate the excessive decline of groundwater level in a main fracture zone adjacent to the cavern. Therefore, the vertical water curtain system is necessary for sustaining the safe groundwater level in the fracture zone.

A preliminary study on the use of analytic hierarchy process for selecting a optimum trenchless excavation method (최적의 비개착공법 선정을 위한 계층분석법의 적용에 관한 기초연구)

  • Kang, Tae-Ho;Chang, Soo-Ho;Choi, Soon-Wook;Lee, Chulho;Cho, Jinwoo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.17 no.6
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    • pp.685-693
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    • 2015
  • There have been high demands for urban underground structures. However, they should be rapidly constructed while maintaining the functions of adjacent structures and road systems especially in urban areas. In this respect, trenchless excavation methods are considered to very effective in minimizing ground displacements during excavation works. A variety of field conditions such as economic, technical and environmental aspects should be taken into consideration when an optimum trechless excavation method is to be chosen in a given condition. Therefore, this study aims to carry out a fundamental study to select an optimum trenchless excavation method by the decision making technique. Especially, AHP (Analytic Hierarchy Process) which is a kind of a multiple attribute decision making process is adopted to consider the opinions of experts and to derive reliable decision criteria. As a result, the weights of key factors and the most effective trenchless methods for different ground conditions were proposed in this study.

Engineering Characteristics of CLSM Using Bottom Ash and Eco-friendly Soil Binder (친환경 고결제와 저회를 활용한 유동성 복토재의 공학적특성)

  • Park, Giho;Kim, Taeyeon;Lee, Yongsoo;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.5
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    • pp.23-29
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    • 2019
  • In general, pipe laying works are performed by constructing underground facilities such as pipes and then refilling the rest of the area with sand or soil. However, there are many problems in the compaction process such as difficulties in tampering around the underground facility and low compaction efficiency. Such problems cause deformation and damage to the underground pipes during refilling work and ultimately cause road sinks. Construction methods using CLSM are one of the typical methods to solve these issues, and recently, studies on CLSM using coal ash, which has similar engineering properties as sand, have been actively performed to protect environment and recycle resources. While many studies have been conducted to recycle fly ash in many ways, the demand for recycling bottom ash is increasing as most of the bottom ash is not recycled and reclaimed at ash disposal sites. Therefore, in order to find bottom ash applications using eco-friendly soil binders that are environmentally beneficial and conform with CLSM standards, this study investigated flow characteristics and strength change characteristics of eco-friendly soil binders, weathered granite soil, a typical site-generated soil, bottom ash, and fly ash mixed soil and evaluated the soil pollution to present CLSM application methods using bottom ash.

Training a semantic segmentation model for cracks in the concrete lining of tunnel (터널 콘크리트 라이닝 균열 분석을 위한 의미론적 분할 모델 학습)

  • Ham, Sangwoo;Bae, Soohyeon;Kim, Hwiyoung;Lee, Impyeong;Lee, Gyu-Phil;Kim, Donggyou
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.23 no.6
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    • pp.549-558
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    • 2021
  • In order to keep infrastructures such as tunnels and underground facilities safe, cracks of concrete lining in tunnel should be detected by regular inspections. Since regular inspections are accomplished through manual efforts using maintenance lift vehicles, it brings about traffic jam, exposes works to dangerous circumstances, and deteriorates consistency of crack inspection data. This study aims to provide methodology to automatically extract cracks from tunnel concrete lining images generated by the existing tunnel image acquisition system. Specifically, we train a deep learning based semantic segmentation model with open dataset, and evaluate its performance with the dataset from the existing tunnel image acquisition system. In particular, we compare the model performance in case of using all of a public dataset, subset of the public dataset which are related to tunnel surfaces, and the tunnel-related subset with negative examples. As a result, the model trained using the tunnel-related subset with negative examples reached the best performance. In the future, we expect that this research can be used for planning efficient model training strategy for crack detection.

Tunnel-lining Back Analysis Based on Artificial Neural Network for Characterizing Seepage and Rock Mass Load (투수 및 이완하중 파악을 위한 터널 라이닝의 인공신경망 역해석)

  • Kong, Jung-Sik;Choi, Joon-Woo;Park, Hyun-Il;Nam, Seok-Woo;Lee, In-Mo
    • Journal of the Korean Geotechnical Society
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    • v.22 no.8
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    • pp.107-118
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    • 2006
  • Among a variety of influencing components, time-variant seepage and long-term underground motion are important to understand the abnormal behavior of tunnels. Excessiveness of these two components could be the direct cause of severe damage on tunnels, however, it is not easy to quantify the effect of these on the behavior of tunnels. These parameters can be estimated by using inverse methods once the appropriate relationship between inputs and results is clarified. Various inverse methods or parameter estimation techniques such as artificial neural network and least square method can be used depending on the characteristics of given problems. Numerical analyses, experiments, or monitoring results are frequently used to prepare a set of inputs and results to establish the back analysis models. In this study, a back analysis method has been developed to estimate geotechnically hard-to-known parameters such as permeability of tunnel filter, underground water table, long-term rock mass load, size of damaged zone associated with seepage and long-term underground motion. The artificial neural network technique is adopted and the numerical models developed in the first part are used to prepare a set of data for learning process. Tunnel behavior, especially the displacements of the lining, has been exclusively investigated for the back analysis.

An Analysis of Safety Zone Appropriateness of Urban Railway Box Structures by Adjacent Excavation Using Machine Learning Technique (머신러닝 기법을 적용한 인접굴착에 따른 도시철도 박스구조물의 안전영역 적정성 분석)

  • Jung-Youl Choi;Jae-Seung Lee;Jee-Seung Chung
    • The Journal of the Convergence on Culture Technology
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    • v.9 no.3
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    • pp.669-676
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    • 2023
  • This study analyzed the relationship between major parameters and numerical analysis results according to various excavations conducted around the urban railway, application of machine learning techniques and verified the scope of influence of the adjacent excavation on the existing urban railway box structure and the appropriateness of the safety area. This study targeted the actual negotiated adjacent excavation works and box structures around the urban railway, and the analysis was conducted on the most representative two-line box structures. The analysis confirmed that the difference in depth of urban railway, excavation depth of adjacent excavation, and depth of underground water level are important parameters, and the difference in excavation depth of adjacent excavation is the parameter that affects the behavior of underground box structures and is an important requirement for setting safety areas. In particular, the deeper the depth of the adjacent excavation work, the greater the effect on the deflection of the underground box structure, and the horizontal separation distance, one of the important requirements for determining the management grade of the existing adjacent excavation work, is relatively small.

The influence of residual stress on the engineering behaviour of rock (잔류응력이 암석의 공학적 거동에 끼치는 영향)

  • 박형동
    • Tunnel and Underground Space
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    • v.5 no.4
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    • pp.363-375
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    • 1995
  • Critical literature review in this study revealed that there can be a significant influence of the residual stress on the engineering properties of rock. The review also showed that few number of research works on the quantification of the influence was attributed to the limitation of the two classical measurement techniques, viz, X-ray diffraction and mechanical relaxation method. In this study, a new way of approach was sought based on the assumption that residual stress up to the failure. A series of hoop tests conducted onthe samples from the limb of Carboniferous Limestone in Clevedon, England, revealed that (i) there is no preferential orientations of microcracks and minerals which have been widely believed as the main source of the strength anisotropy of rock; (ii) the anisotropy of the tensile strength of the limestone results from the influence of the residual stress; (iii) since jointing commenced within the fold, residual stored strain energy has been released preferentially in the direction perpendicular to the major joints(o$^{\circ}$ and 90$^{\circ}$); (ⅳ) during the hoop test making it much easier to create tensile fracture in these directons, viz 45$^{\circ}$ and 135$^{\circ}$)was released during the hoop test making it much easier to create tensile fracture in these directions, viz 45$^{\circ}$and 135$^{\circ}$;(v) the direction in which the stored strain energy may be presumed to be the least, required the greatest work to cause failure.

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An Analytical and Experimental Study on the Mechanical Behavior of Excavating Turnels beneath the Roadway (공용중 도로하부의 굴착터널 해석 및 계측 연구)

  • Chung, Kuang-Mo;Bang, Myung-Seok
    • Journal of the Korean Society of Safety
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    • v.27 no.5
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    • pp.99-104
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    • 2012
  • A turnelling work beneath roadways or railways in use is unsafe and dangerous. A turnelling method should be analytically and experimentally studied to verify stability and safety of excavating works by construction step. The conventionally analytical method was ineffective in computational time and cost, so the new analytical method named homogenuity method, was developed and verified compared with analytical results. That method was applied to parameterly study the effect of distance of steel supports and overburdening height of soil. It showed that the homogenuity method was very practical and effective in step-by-step analysis considering construction sequences. A measuring device was set at the construction field and mechanical behavior was monitored during construction. Measuring values are larger than analytical values because impact of inserting steel pipes, lowering level of underground water and vibration of passing vehicles affected soil density during construction, but those values were within allowable limits.

A Study of the 3D Unmanned Remote Surveying for the Curved Semi-Shield Tunneling

  • Lee, Jin-Yi;Jun, Jong-Woo
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.1791-1796
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    • 2005
  • Semi-shield tunneling is one of the propulsion construction methods used to lay pipes underground between two pits named 'entrance' and 'destination', respectively. Usually a simple composition, such as 'a fiducial target at the entrance+a total station (TS)+a target on the machine', is used to confirm the planned course. However, unavoidable curved sections are present in small-sized pipe lines, which are laid after implementation of a road system, for public works such as waterworks, sewer, electrical power, and gas and communication networks. Therefore, if the planned course has a curved section, it is difficult to survey the course with the abovementioned simple composition. This difficulty could be solved by using the multiple total stations (MTS), which attaches the cross type linear LED target to oneself. The MTS are disposed to where each TS can detect the LED target at the other TS or the base point or the machine. And the accurate relative positions between each MTS and target are calculated from measured data. This research proposes the relative and absolute coordinate calculation algorithm by using three MTS to measure a curved course with 20m curvature at 30m maximum distance, and verifies the algorithm experimentally.

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Worldwide Trends in the Research Topics for the Vehicle Tunnel Ventilation (도로터널 환기관련 연구동향)

  • 이창우
    • Tunnel and Underground Space
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    • v.12 no.3
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    • pp.152-157
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    • 2002
  • Optimal design of the long tunnels with large cross sections essential for the effective development of the limited land in Korea becomes more and more difficult owing to the constantly changing social, economic, environmental and technological factors. Deficiency of the domestic research works till now on the elementary topics on tunnel ventilation retards progress on developing the key technologies urgently required for designing and managing the long and large tunnels. This paper aims at identifying the subjects on which research must be carried out for the construction and management of vehicle tunnels in Korea by means of scrutinizing the contents of the publications since 1991 at the International Symposium on Aerodynamic and Ventilation of Vehicle Tunnels, the only international conference on the tunnel ventilation.