• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.5
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• pp.529-545
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• 2012

Three-dimensional (3D) finite element analyses have been performed to study the behaviour of a single pile to open face tunnelling in stiff clay. Several key factors such as tunnelling-induced ground and pile settlement, and shear transfer mechanism have been studied in detail. Tunnelling resulted in the development of pile settlement larger than the Greenfield soil surface settlement. In addition, due to changes in the shear transfer between the pile and the soil next to the pile with tunnel advancement, axial force distributions along the pile change drastically. The apparent allowable pile capacity was reduced up to about 30% due to the development of tunnelling-induced pile head settlement. The skin friction on the pile was increased with tunnel advancement associated with the changes of soil stresses and ground deformation and hence axial pile force distribution was reduced. Maximum tunnelling-induced tensile force on the pile was about 21% of the designed pile capacity. The zone of influence on the pile behaviour in the longitudinal direction may be identified as ${\pm}1$-2D (D: tunnel diameter) from the pile centre (behind and ahead of the pile axis in the longitudinal direction) based on the analysis conditions assumed in the current study. Negative excess pore pressure was mobilised near the pile tip, while positive excess pore pressure was computed at the upper part of the pile. It has been found that the serviceability of a pile experiencing adjacent tunnelling is more affected by pile settlement than axial pile force changes.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.13-20
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• 1998

The moving behaviour of Yellowtail Seriola quinqueradiata schools in the main-net of a large scale set-net was investigated in relation to the catching function of the funnel-net by a scanning sonar. The investigation was took place in the Kishihata set-net fishing ground located in Nanao city Ishigawa prefecture, Japan from Nov. 9 to Nov. 13, 1992. The obtained results are summarized as follows; 1. Fish schools showed the greatest number at the playground in the morning and at the bag-net in the afternoon. The fish schools remained long time in the main-net. 2. The rate of fish school through the funnel-net was smaller than that of fish school which is though the playground and bag-net. Because the Yellowtail school changed the shape of school in passing the funnel-net. 3. The rate of entering the bag-net was 24%, among the fish school heading to the outer funnel-net. But, the rate of escaping to the playground was 27%, among the fish school heading to the inner funnel-net. It seems that the structure of the outer funnel-net was not enough to lead the fish to the bag-net. However, the structure of the inner funnel-net was very effective at preventing escape. 4. It is appropriate to haul the net in the morning in considering the number of accumulated fish in the bag-net during the survey.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.57-67
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• 1997

The objective of present paper is to investigate elasto-plastic behaviour and estimate the resistance capacity of a beam-shear wall structural system against earthquake ground accleration exciations. Pushover analysis is adopted to estimate inttiate and post stiffnesses and yielding point for inelastic response analysis in LPM (Lumped Parameter Mass) model, and modified Clough model is used as the hysteresis rule of each story. Three earthquake waves are used in the analysis but their peak ground accelerations are changed to be 0.12g, 0.24g. It is assumed that the earthquakes act in the longigtudianl direction of a 25 Story apartment building which consists of two some unit plan. The distribution of story ratio and ductility ratio are estimated and discussed within Korean, Japanese code and UBC.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.3
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• pp.299-310
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• 2014

Nationally, tunnel and underground constructions are necessary for the environmental sustainability and the efficient use of land space. For the importance of eco-friendly circumstances, 2-arch or large road tunnel has been designed so far. However, such a 2-arch or large tunnel has problems in terms of cost, constructability, construction period, and maintenance. Therefore, in this study, tunnel behavior and stability of rock pillar according to the pillar width and cover depth for parallel tunnels are investigated by performing FE analysis and using empirical formula. According to the results, Rock pillar is reinforced for distributed vertical load by Tie-Bolt due to unpredicted ground deformation, and the reinforced rock pillar's behaviour from the FE analysis shows a quite good agreement with field measurement. According to ground conditions, if the pillar width of the parallel tunnels is reduced, it can be more efficient in use of the tunnel space compared to previous tunnels.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.55-62
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• 2005

This paper is the results of experimental and numerical works on analyzing the geotechnical engineering behavior and characteristics of excavated clay slope formed by the method of excavated replacement which is one of treatments in soft soil ground. For the centrifuge model tests, models of excavated clay slope were prepared by remolding the marine clayey soil sampled from the field. Tests were performed with changing the slope to investigate the behavior of them. On the other hand, numerical analyses were carried out to analyze the change of safety factor against instability of slope with time. Changes of pore water pressure, shear strength and displacement were also investigated. As results of centrifuge model tests with slopes of 1:1.5 and 1:3 using the confining body of simulating the effect of excavation, for the case of 1:1.5, slope failure occurred right after remove the confining body whereas relatively small displacements within the range of 3.2mm, implying to maintain the stability of slope, were observed for the case of 1:3 slope. From the results of numerical analyses using the software of PLAXIS to investigate the stability of slope after excavation, the minimum safety factor against slope failure was 1.28 for the case of 1:3 slope. The further researches in the future are required with considerations of build up of static pore water pressures during acceleration of centrifuge, depth of excavation influencing the behavior of the slope and permeability of the slope since excavation of the slope was not simulated well resulted from the limitations of apparatus at the stage of excavation during the centrifuge tests.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.95-109
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• 2018

Recently, GRS (Geosynthetic Retaining Segmental) wall has been widely used as a method to replace concrete retaining wall because of its excellent structural stability and economic efficiency. It has been variously applied for foundation, slope, road as well as retaining wall. The GRS wall system, however, has a weak point that is serious crack of wall due to stress concentration at curved part of it. In this study, therefore, behaviour of GRS wall according to shape of it, shich has convex and concave, are analysed and compared using Finite Element analysis as the fundamental study for design optimization. Results including lateral deflection, settlements of ground surface and wall obtained from 2D FE analysis are compared between straight and curved parts from 3D FE analysis.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.113-125
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• 2002

Ground improvement technique of cement stabilization via Deep Soil Mixing with dry cement is gaining popularity, particularly in Japan and other parts of Southeast Asia and in Scandinavia. Cement can be mixed with deep soft clay deposits, typical of marine environments, to improve the bearing capacity and/or reduce the compressibility of the material so that an otherwise poor site can be developed. However, the strength/deformation behaviour and resulting soil structure of the clay-cement mixture is presently not well understood with respect to both dry and wet mix methods. An extensive laboratory test was carried out to determine the mechanical characteristics of kaolin-cement, with some brief examination of the effects of curing environment. Laboratory tests include triaxial tests, unconfined compression tests, isotropic consolidation testis and oedometer tests. Cement contents up to 10 percent were considered and water curing was employed. Samples were cured for 7 to 112 days while submerged in distilled water. Conventional laboratory tests were also performed. In this paper, the laboratory testing program is described and various sample preparation techniques are discussed. Preliminary triaxial compression test results and trends at varying moisture contents, cement contents, confining pressures and curing times will be presented.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.319-332
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• 2002

Domestic masonry railroad tunnel lining consists of red bricks or granite stone blocks and mortar. It is necessary to evaluate the behaviour of the masonry tunnel lining during an earthquake because the lining was constructed without the consideration of seismic loads. In this study, a methodology to evaluate the seismic resistant capacity of masonry tunnel linings was proposed, i.e. material property evaluation and seismic analysis technique. The red brick masonry tunnel lining is arrayed with multi-layers composed of 3 to 5 bricks depending on ground conditions and each brick is attached with mortar. Equivalent property concept was adopted to consider the stiffness difference among the red brick material itself and joints between bricks. Response spectrum analysis was performed by considering ground-structure interactions. A parametric study was performed to figure out the effect of relative stiffness between the lining and rock mass on the seismic behavior. A resonable countermeasure to minimize the earthquake-induced damage was also proposed.

• Journal of the Korean Geosynthetics Society
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• v.14 no.1
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• pp.11-21
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• 2015

This study aims at investigating of the behavioral characteristics of foundation ground subjected to a strip load in anisotropy. Using marine clays sampled at Shihwa area, a series of laboratory tests including triaxial compressive test, plane strain compressive and expansion tests that allows horizontal deformation only and zero strain (${\varepsilon}_2$) in the direction of intermediate stress (${\sigma}_2$) are conducted. In addition, a numerical analysis using parameters obtained from the tests is carried out. In the numerical analysis, Cam-clay model that simulates the behavior of natural deposited clay properly is adopted. The analysis results show that the vertical displacements of the plane strain compressive tests are relatively larger than those of triaxial compressive tests by 18-25%. Likewise, the horizontal displacements is 13-19% larger.

• Journal of Korea Water Resources Association
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• v.32 no.3
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• pp.301-310
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• 1999

In this paper a numerical model and two analytical models in the hydraulically connected stream-aquifer system were analyzed to compare the induced infiltration rate curves derived from each model. And we also examined the effects of anisotropy of hydraulic conductivity and the direction of the ambient ground water flow on the quantification of the induced infiltration rate. The induced infiltration rate curve determined by models is very simple and useful for estimating the induced infiltration rate since it contains only four physical variables such as the induced infiltration rate, the pumping rate, the distance between the pumping well and the stream, and the ambient ground water flow rate. Under the conditions tested in this paper the induced infiltration rate curves resulted from the Wilson's analytical model and FEWA numerical model were in good agreement, and the anisotropic ratio of hydraulic conductivity was evaluated as a physical factor which influences the behaviour of the induced infiltration rate curve. The methods and results of the paper might Icad to improve the understanding of the induced infiltration phenomenon and can be applied to the planning and disign of pumping well and the optimal determination of the induced infiltration rate and pumping rate for water quality management of the water supply wells.