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List of products by author: H. Choi
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A Numerical Study on Mechanical Behav iour of Cross Passage Constructed by Arti ficial Ground Freezing Method
Abstract: In subsea tunnel constructions, where water pressure is higher than 20 bars, the convention grouting technologies are restricted to apply because they cannot implement appropriate water cut-off. For these extreme conditions, the artificial ground freezing (AGF) method can be an effective alternative, especially for constructing cross passages of a subsea tunnel through highly-fractured fault...
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Application of Artificial Neural Network for Prediction of Surface Settlement During Shield TBM
Abstract: Surface settlement induced by shield TBM tunnel excavation in shallow soft ground can threaten the stability of adjacent structures in urban areas. Controlling the ground surface settlements occurred during tunneling is one of the key issues for tunneling engineers. Numerous researches for the prediction of surface settlement have been attempted along with analytical, empirical and/or numerical...
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Application of Liquid Air Refrigerant to Artificial Ground Freezing in Enclosed Subsea Tunnels
Abstract: Subsea tunnels are highly vulnerable to seawater intrusion caused by high water pressure during construction. The artificial ground freezing (AGF) will be a promising alternative to conventional reinforcement methods. Use of brine as a refrigerant is disadvantageous because of its longer freezing time due to the high boiling point. On the other hand, liquid nitrogen, which can freeze saturated...
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Classification of surface settlement of stacked twin tunnels by machine-learning
Abstract: To ensure the safe operation of tunnel boring machines (TBMs) in urban areas, surface settlements should be monitored at several levels such as the alert, action, and alarm level, to prevent any damage to nearby infrastructures. In this study, the random forest (RF) machine learning model was implemented to predict the surface settlement levels using a database collected from a Hong Kong subway...
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Crack Detection in Pillar Structure Using Infrared Thermo-graphic Imaging
Abstract: The use of underground space in metropolitan city is increasing. More than 90% of flood damage occurs in the downtown area of metropolitan cities. To prevent and/or minimize flood-induced damage, an underground rainwater detention cavern, to be built underneath existing structures, was proposed by Seo et al. (2012a). As for underground caverns to be built for flood control, multi-caverns will...
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Effect of sample preparation and freezing temperature on constitutive modeling for frozen soil in subsea tunnel...
Abstract: When high water-pressure is expected during constructing cross passages in subsea bored tunnels, convectional grouting technologies are not appropriately adapted to water cut-off. In this extreme condition, the artificial ground freezing (AGF) technique can be a promising alternative for constructing cross passages through highly-fractured fault zones. An appropriate experiment procedure to...
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Harmony Search Algorithm to Predict Anomalous Zone Ahead of Tunnel Face
Abstract: During tunnelling work, emergence of unpredicted fault or anomalous zone leads to delay of construction work or increase of construction cost hampering construction ability. Predicting the anomalous zone ahead of tunnel face in advance can thus prevent time and economic loss. This raised the demand to develop a prediction technique that detects anomalous zones ahead of a tunnel face during...
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Importance of face pressure and tail void grouting on numerical modeling of shield TBM tunneling through soft ground...
Abstract: Shield tunneling is now becoming a general trend in tunnel excavation. Despite the growing importance of shield tunneling, a prevalent standard for its numerical analysis has not been established yet, due to difficulty in appropriate implementation of face pressure, tail void grouting, and continuous excavation steps during shield TBM tunneling. Since there are various empirical methods to...
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Influence of system parameters on thermal performance of energy slab installed in underground structures
Abstract: The energy slab is a ground coupled heat exchanger equipped in building slab structures, which has a similar layout to the horizontal ground heat exchanger (GHEX). As the energy slab is generally installed at the shallow depth, its thermal performance is notably inferior to the conventional vertical GHEXs. This is because the energy slab cannot use the high thermal capacity of a deep...
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Laboratory Study on Characteristics of Foam - Conditioned Weathered Granite Soil
Abstract: The weathered granite soil that is widely distributed in the Korean peninsula has unique characteristics compared to typical sandy or clayey soils. When tunnelling the ground consisting of the weathered granite soil by the earth pressure balance (EPB) shields, it is necessary to evaluate the effect of foam conditioning on the behavior of the weathered granite soil. In this study, a...
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Numerical Modelling for Effective Thermal Conductivity of Frozen Soil for Designing Artificial Ground Freezing
Abstract: The artificial ground freezing technique can be a promising tool for constructing cross passages of a subsea tunnel through highly-fractured fault zones. To design the artificial ground freezing method, it is very important to estimate the thermal conductivity of unfrozen and frozen soils. Because the direct measurement of thermal conductivity of frozen soil is a complex and time-consuming task...
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Optimum Freezing Pipe Arrangement for Subsea tunnel Cross Passage Construction
Abstract: Nowadays, linking countries and continents in the global transportation systems becomes an utmost challenge of civil engineering, which attracts a growing interest in construction of subsea tunnels. Among many parts of a subsea tunnel, cross passages connecting parallel twin tunnels, play a role to equilibrate the air pressure generated by passage of high speed trains, and as an emergence...
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Risk Analysis using Bayesian Networks Applicable to Shield TBM Tunnels
Abstract: The tunnel boring machine (TBM) system, the most representative mechanized tunneling method, has been widely adopted in numerous tunneling projects. It is also quite environmentally friendly, exhibiting minimized noise and vibration when compared with conventional tunneling methods. Moreover, it provides considerable economic benefits that allow for high advance rate for long drives during...
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The study of support pattern in modern rock TBM with a pressurized ring beam system
Abstract: The pressurized ring beam has been devised to improve the performance of primary support by applying pressure to circular steel ribs (i.e., ring beams) during operating a modern rock TBM. In this paper, an appropriate support pattern is suggested for the pressurized ring beam in consideration of typical ground conditions for the modern rock TBM. A case study has been performed with respect to...
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