• Proceedings of the Korean Geotechical Society Conference
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• 1993.10a
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• pp.51-56
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• 1993

This paper presents the FEM anlysis results performed to assess the applicability of Horizontal Jet Grout Roofing, and of ground improvement methods for tunneling in soft ground. Horizontal Jet Grount Roofing Method is applicable to ensure the stability of tunnel face in non-cemeted alluvial strata under high ground water pressure. For applying this method, to ensure the reliability, the Horizontel Jet Grout Roofing should be double lined with pre-grouting to reduce the water inflow during the jet grouting.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.823-831
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• 2018

The most important issue during shield TBM tunneling in soft ground formations is to appropriately control ground surface settlement. Among various operational conditions in shield TBM tunneling, the face pressure and backfill pressure should be the most important and immediate measure to restrain surface settlement during excavation. In this paper, a 3-D hydro-mechanical coupled FE model is developed to numerically simulate the entire process of shield TBM tunneling, which is verified by comparing with real field measurements of ground surface settlement. The effect of permeability and stiffness of ground formations on tunneling-induced surface settlement was discussed in the parametric study. An increase in the face pressure and backfill pressure does not always lead to a decrease in surface settlement, but there are the critical face pressure and backfill pressure. In addition, considering the relatively low permeability of ground formations, the surface settlement consists of two parts, i.e., immediate settlement and consolidation settlement, which shows a distinct settlement behavior to each other.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.89-94
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• 1996

The use of shield is increasing day by day, because it's method is advantageous tunneling method to soft and collapsible ground. In case of analyzing shield tunnel by FEM, short term behavior of ground by initial heaving and tail void closure and long terms of it because of consolidation by changes of pore pressures in clay must be considered. In this paper, the shield tunneling construction stages was analyzed from 2 dimensional elasto - viscoplastic finite element program used Mohr - Coulomb yield criterion but not considered the changes of pore pressures. The object of investigation was N - 2 Tunnel. Since the good results of analysis compared to the measured behavior of ground for heaving, tail void closure and liner installation, this results can be applied to design and construction of shield tunneling for the subways, sewage lines etc.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.110-117
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• 2006

Boulder detection methods and its compensation is discussed with consideration of boulder conditions in soft ground tunneling by shielded TBM. For analysis of proper compensation methods for boulder obstruction, its removal costs and cases on eight projects are presented. Compensation for boulder obstruction removal by volume or weight is not practical for most tunneling situation, but compensation by crew time is probably the most equitable method. If boulders are anticipated on project, boulder removal plan must be considered with proper equipment selection.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.95-102
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• 2003

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.95-103
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• 2010

In this paper, a new soft ground tunneling technique termed the PNT method(Pre-Nailed Tunneling Method) is studied. Mechanism of the method is investigated in terms of theoretical and numerical approaches. The pre-nailing effects are validated by performing two dimensional numerical analyses. It is identified that the method is successful in soft grounds, and greatly efficient in reducing the ground deformation by nailing the ground. To develop the design guidelines of the method, numerical parametric analyses on the installation range and angle were also carried out.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.133-140
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• 1997

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.143-154
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• 2016

This study investigated the occurrences, causes, and mitigation of the recent ground subsidence and underground cavity generation events in Korea. Two main causes of ground subsidence are (1) the soil erosion by seepage during tunneling and earth excavation and (2) the damage of underground pipes. The main cause of the soil erosion during tunneling was the uncontrolled groundwater flow. Especially, when excavating soft grounds using a tunnel boring machine (TBM), the ground near TBM operation halt points were found to be the most vulnerable to failure. The damage of underground pipes was mainly caused by poor construction, material deterioration, and differential settlement in soft soils. The ground subsidence during tunneling and earth excavation can be managed by monitoring the outflow of groundwater and eroded soils in construction sites. It is expected that the ground subsidence by the underground pipe damage can be managed or mitigated by life cycle analysis and maintenance of the buried pipes, and by controlling the earth pressure distribution or increasing the bearing capacity at the upper ground of the buried pipes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.87-94
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• 2010

This study mainly focused on the subsurface settlement due to shallow and deep tunneling in sandy ground. In order to figure out theoretical deformation patterns in association with the ground loss during the progress of tunneling, laboratory model tests using aluminum rods and finite element analyses using the CRISP program were carried out. As a result of comparison between the model test and the finite element analysis, the similar deformation patterns were found. In addition, it was identified that the most K values obtained from both the FEA and the model tests were distributed between Dyer et al. (1996) and Moh et al. (1996) of the field observation data. Based on the model test data, the linear equation of K for the sandy soil could be obtained.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.483-496
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• 2013

This paper presents the shield TBM technology in soft ground tunnelling. In order to perform this study, a scale model test was carried out using the developed small scaled shield TBM machine. The various instrumentations were conducted during the simulation of tunnelling. In addition, the ground behavior due to the shield TBM operation parameters was measured during the simulation. Based on the simulation results, the stability of the ground was evaluated and the fundamental shield TBM tunnelling technique in the soft ground was suggested. In conclusion, design's reliability through laboratory small scale model test about Shield-TBM section was obtained, and both the improvement plan for safety during construction and the construction plan for securing airport runway's safety during tunnel passing by Shield-TBM propulsion were suggested.