• The Journal of Engineering Geology
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• v.6 no.3
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• pp.111-118
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• 1996

In general, a three dimensional ground behaviour during tunneling is simulated by using two dimensional analysis programs in consideration of a certain ratio of stress or strain distribution to take into account the effect of construction stage by a tunnel face advance. A series of trree dimensional analyses was conducted to deduce a normalized displacement (surface or crown settlement) curve in longitudinal direction, of which curve is reflecting an effect of a tunnel advance under a various condition. And, by using try and error technique, two dimensional analyses were carried out to determine an optimum stress distribution ratio for a settiement curve coincided with the curve obtained by three dimensional analyses. Finally, monitored results from a subway tunnel were compared with two dimensional analysis results for varification of the deduced stress distribution ratio as well as the two dimensional analysis program employed in this study.

• Journal of the Korean GEO-environmental Society
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• v.11 no.2
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• pp.5-11
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• 2010

Abandoned mines release acid mine drainage and cause the contamination of soil and crops around the mine area. The objective of current study is to evaluate effect of mine on the soil and crop contamination. Soils, water, and crops were collected and analyzed, and the heavy metal data were classified into types of the soil, types of crops, and distance from the minehead. Surface soils of the mine area were highly contaminated with heavy metals, especially with zinc and lead. Tailings and cultivated paddy soils were also highly contaminated. Heavy metal concentrations upon distance from minehead decrease steadily as the distance from the minehead increase. The correlation between heavy metals was extracted from soils and the content in the rice samples showed a positive relation for arsenic and cadmium but not a meaningful relation for other metals.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.243-252
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• 2019

Recently, as the utilization of underground space increases, the demand for underground excavation increases. In this study, the concrete mixture with a new material was used to develop and evaluate the stability of the CS-H wall that can greatly minimize the problems of existing wall and minimize the impact of ground depression and surrounding ground that may occur in the future for excavation of over 30 m deep in urban areas. The fiber reinforcement formulation of steel fibers, synthetic fibers, and glass fibers, along with fine aggregate parts of PS-ball and ferronickel, were mixed. The Mixture ratios were determined by conducting slump test compresive strength test, modulus of elastic test, flexural strength test, splitting tensile strength test and conductivity test. As a result of the test, the steel fiber mixture showed very good results compared to other reference values in all items, and it is considered to be the most suitable for the CS-H wall to be developed.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.189-206
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• 2003

During tunnel excavation in urban area a systematic monitoring is important for the purpose of determination of support type and quantity, as well as for the control of stability of both surface structures and the tunnel itself due to the frequently, and in many cases, abruptly changing ground condition. In Austria absolute displacement monitoring methods have replaced relative displacement measurements by geodetic methods to a large extent. Prompt detection of weak ground ahead of the tunnel face as well as better adjustment of excavation and support to the geotechnical conditions is possible with the help of the improved methods of data evaluation on sites. Deformation response of the ground to excavation starts ahead of the tunnel face, therefore, the deformation and state of the tunnel advance core is the key factor of the whole deformation process after excavation. In other words, the rigidity and state of the advance core play a determining role in the stability of both surface structures and the tunnel itself. This paper presents the results from detailed three-dimensional numerical studies, exploring vertical displacements, vector orientations and extrusions on tunnel face during the progressive advancement for the shallow tunnel in various geotechnical conditions.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.75-83
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• 2011

Emerging issues related with fully coupled Thermo-Hydro-Mechanical (THM) behavior of unsaturated soil demand the development of a numerical tool in diverse geo-mechanical and geo-environmental areas. This paper presents general governing equations for coupled THM processes in unsaturated porous media. Coupled partial differential equations are derived from three mass balances equations (solid, water, and air), energy balance equation, and force equilibrium equation. With Galerkin formulation and time integration of these governing equations, finite element code is developed to find nonlinear solution of four main variables (displacement-u, gas pressure-$P_g$), liquid pressure-$P_1$), and temperature-T) using Newton's iterative scheme. Three cases of numerical simulations are conducted and discussed: one-dimensional drainage experiments (u-$P_g-P_1$), thermal consolidation (u-$P_1$-T), and effect of pile on surrounding soil due to surface temperature variation (u-$P_1$-T).

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.2
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• pp.171-182
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• 2004

This study is focused on finding out the mechanical behavior of pillars and the ground adjacent to the tunnel depending on the central tunnel size and the invert during the construction of 2 arch tunnels in the sandy ground. Model tests were performed in the trap door system, which was composed of 3 separately movable plates. Central pillar was installed on the central movable plate to measure the pillar loads during the excavation of pilot tunnel and the main tunnel. The load-transfer and the loosening load were measured at the bottom plates adjacent to the 2 arch tunnels. The ground settlement and displacement of the tunnel lining were also measured. As results, not only pillar load but also the load transfer mechanism was influenced by the construction sequences, central tunnel size, and the invert.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.207-214
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• 2005

The reflected signals from the defects of a pile and the boundaries between the pile and soils are analyzed to evaluate the integrity of drilled shafts in the impact-echo test. Signals varied according to both of the stiffness ratio of the pile to defects and that of the pile to surrounding soils. Model tests using the small size pile in the laboratory and numerical analyses have limitations in finding the characteristics of the signals due to different stress wave characteristics and unreliable modelling for the interaction between the pile and soils respectively. Full scale testing piles which have artificial defects are installed by the actual construction method and they were used to investigate the characteristics of reflected signals according to defects and the stiffness ratios of the pile to soils around.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.511-524
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• 2015

Groundwater causing subsidence in limestone mines is uncommon, and thus relatively poorly investigated. This case study investigated the cause and possibility of future subsidence through an evaluation of ground stability at the Samsung limestone mine, Chungcheongbuk-do. The ground near the mine area was evaluated as unstable due to rainfall permeation, and subsidence in the unmined area resulted from groundwater level drawdown. Future subsidence might occur through the diffusion of subsidence resulting from the small thickness of the mined rock roof, fracture rock joints, and poor ground conditions around the mine. In addition, the risk of additional subsidence by limestone sinkage in corrosion cavities, groundwater level drawdown due to artificial pumping, and rainfall permeation in the limestone zone necessitates reinforcements and other preventative measures.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.169-183
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• 2007

Numerical analysis was performed to investigate the behavior of rammed aggregate piers (RAP) in soft ground with various interface conditions, area replacement ratio, aspect ratio and surcharge loads of pile and soil. And field modulus load test was carried out to predict the input parameters. Field prototype (unit cell) tests are in progress to compare the result of numerical analysis. Also a modified load transfer equation of RAP on soft foundation was proposed. According to the results, the behavior of RAP depended on such as interface conditions, settlement characteristics (free strain) and stress concentration ratio. On the other hand, maximun stress concentration ratio increased as area replacement ratio and aspect ratio increased, and it was remarkably affected by surcharge loads.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.15-26
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• 2005

This paper concerns the assessment of impact of deep excavation on surrounding environment with emphasis on the groundwater lowering. Fundamentals of ground excavation and groundwater interaction were reviewed and the stress-pore pressure coupled analysis approach as a tool for assessment was introduced. A case study concerning the use of coupled analysis for deep excavation design was presented. Implications of the finding from from this study were discussed.