• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.6
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• pp.703-714
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• 2010

This paper proposes an approach for staged finite element modeling with coupled seepage and stress analysis. The stage modeling is based on the predefined inter-relationship between the base model and the unit stage models. A unit stage constitutes a complete finite element model, of which the geometries and attributes are subject to changes from stage to stage. The seepage analysis precedes the mechanical stress analysis at every stage. Division of the wet and dry zone and the pore pressures are evaluated from the seepage analysis and used in determining input data for the stress analysis. The results of the stress analysis may also be associated with the pore water pressures. For consolidation analysis, the pore pressure and the displacement variables are mixed in a coupled matrix equation. The time marching solution produces the dissipation of excess pore pressure and variation of stresses with passage of time. For undrained analysis, the excess pore pressures are computed from the stress increment due to loading applied in the unit stage and are used in revising the hydraulic head. The solution results of a unit stage are inherited and accumulated to the subsequent stages through the relationship of the base model and the individual unit stages. Implementation of the proposed approach is outlined on the basis of the core procedures, and numerical examples are presented for demonstration of its application.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.189-198
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• 2006

This paper concerns the finite element (FE) modeling approach for NATM tunneling in water bearing ground within the framework of stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as soil-water characteristics, location of hydraulic boundary conditions, the way of modeling drainage flow, among others. The results indicate that the soil-water characteristics plays the most important role in the tunneling-induced settlement characteristics. Based on the results, modeling guidelines were suggested for stress-pore prssure coupled finite element modeling of NATM tunneling.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.5-20
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• 2006

This paper concerns the finite element (FE) modeling approach for NATM tunneling in water bearing ground within the framework of stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as soil-water characteristics, location of hydraulic boundary conditions, the way of modeling drainage flow, among others. The results indicate that the soil-water characteristics play the most important role in the tunneling-induced settlement characteristics. Based on the results, modeling guidelines were suggested for stress-pore pressure coupled finite element modeling of NATM tunneling.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.465-474
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• 2005

This paper presents the interaction effect between tunneling and groundwater on tunnel behavior. A parametric study is then conducted on the various tunneling situations frequently encountered in Seoul area using a 3D stress-pore pressure coupled finite-element model with emphasis on the effects of ground and lining permeabilities. It is shown that the ground and lining responses are significantly influenced by the relative permeability between the ground and the lining, and that the circumferential pre-grouting is effective in minimizing the tunnelling and groundwater interaction.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.415-424
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• 2004

This paper presents the effect of groundwater on tunneling performance. The interaction between the tunneling and groundwater was examined using a 3D stress-pore pressure coupled finite-element analysis, The results of the 3D coupled analysis were then compared with those of a total stress analysis. Examined items included pore pressures around lining and lining forces. Also examined include face displacements and ground surface movements, The results indicated that the interaction between the tunneling and ground water significantly increases the lining forces and ground deformations, and that the effect of ground water on tunneling can only be captured through a fully coupled analysis, Implementations of the findings from this study arc discussed in great detail.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.33-46
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• 2004

This paper presents the effect of groundwater on tunnel excavation. Fundamental issues in tunneling under high groundwater table are discussed and the effect of groundwater on tunnel excavation was examined using a 3D stress-pore pressure coupled finite-element analysis. Based on the results the interaction mechanism between the tunnelling and groundwater is identified for cases having different lining permeabilities. Examined items include pore pressures around lining and lining stresses. Face deformation behavior as well as ground surface movement patterns was also examined. Besides, the effect of grouting pattern was investigated. The results indicated that the effect of groundwater on tunnel excavation increases lining stresses as well as ground movements, and that the tunnel excavation and groundwater interaction can only be captured through a fully coupled analysis. Implementations of the findings from this study are discussed in great detail.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.13-20
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• 2010

This paper presents the results of a numerical investigation on the ground deformation in deep excavation with emphasis on the groundwater lowering. Using the stress-pore pressure coupled analysis Consideration to the effect of ground excavation and groundwater interaction were carried out and a series of two-dimensional finite element model was employed to perform a parametric study on a wide range of soil profile and initial ground water table condition.

• Geomechanics and Engineering
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• v.10 no.4
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• pp.437-454
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• 2016

Wellbore instability problem is one of the main problems that met frequently during drilling, particularly in high temperature, high pressure (HPHT) formations. There are large amount of researches about wellbore stability in HPHT formations, which based on the thermo-poroelastic theory and some achievements were obtained; however, few studies have investigated on the fully coupled thermo-poroelastoplasticity analysis of wellbore stability, especially the analysis of wellbore stability while the filter cake formed. Therefore, it is very necessary to do some work. In this paper, the three-dimensional wellbore stability model which overall considering the effects of fully coupled thermo-poroelastoplasticity and filter cake is established based on the finite element method and Drucker-Prager failure criterion. The distribution of pore pressure, wellbore stress and plastic deformation under the conditions of different mud pressures, times and temperatures have been discussed. The results obtained in this paper can offer a great help on understanding the distribution of pore pressure and wellbore stress of wellbore in the HPHT formation for drilling engineers.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.17-31
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• 2011

This paper presents the results of a numerical investigation on the behavior of earth retaining wall system with emphasis on the groundwater lowering. Using the 2D stress-pore pressure coupled analysis, the effects of ground excavation and groundwater interaction were examined using wall horizontal deformation, ground surface movement, plastic strain pattern, effective stress distribution and axial stress of strut. In addition, based on the results from a parametric study on a wide range of soil profile and initial ground water table level, the ranges of wall displacement and ground deformation were suggested quantitatively.