• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.984-991
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• 2008

In this study, to evaluate the slope and tunnel stabilization method using pc cable with bulbed. To estimate the application of tunnel support using field tests and numerical analysis results. The reinforcement effects of slope stabilization method reinforced by PC cables were estimated compared with conventional soil nail system that reinforce the slope using rebar.

• Tunnel and Underground Space
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• v.15 no.3 s.56
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• pp.185-194
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• 2005

Recently, the surrounding rock mass is understood as the major support system for the tunnel constructed in the rock mass. Generally, the rock mass contains many discontinuity planes such as joints, and thus, the tunnel behavior in the rock mass is governed by the characteristics of the discontinuity planes. In this study, the behavior of tunnel in jointed rock mass is studied by model tests and numerical analyses. The results shows that the behavior of tunnel depends on the different initial stress conditions, in case that the tunnel is excavated in the ground without any joints. When a joint is located near the tunnel, the pound stress and displacement tend to increase between the tunnel and the joint.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.321-331
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• 1998

A reliable analysis of tunnelling is needed to accomplish technically sound design and safe and economical construction. For the reliable analysis, a series of procedures of construction which include excavation and support stages must be considered. In this study, rock-support response behavior is studied and simulated in 2-D and 3-D finite element methods. Through the analysis of rock-support response behavior, the effects of the properties of shotcrete on the load distribution ratio can be quantified. The load distribution ratios for different rock types, different unsupported spans and various lateral earth pressure coefficients can be determined from the results of the 3-D finite element analysis. This load distribution ratios can be applied to a practical tunnel design through understanding of the trend of those various factors affecting the rock-support interaction.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.166-178
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• 1991

Using FLAC, which is an explicit finite difference code written for analysis of problems in geotechnical engineering, a particular example 2 in the Korean Geothechnical Society News has been analysed. The elastoplasticity formulation in FLAC assumes an elastic, perfectly plastic solid in plane strain which conforms to a Mohr-Coulomb yield condition. During tunnel excavations by stages, stresses and diaplacements in region around the tunnel varies according to distance from the face of tunnel and installation of tunnel supports, and soon. In this analysis, the three dimensional support effect of the rock mass during the process of excavation is simulated by using the stress distribution method, and varying the material constants of shotcrete in each stage also considered. The maximum convergency is occured at the crown of the tunnel and estimated to be about 12mm.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.139-146
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• 1999

Geological and geotechnical surveys, in general, should precede the excavation to ensure the stability of the tunnel md should be followed up according to the various geological condition during the excavation. However actually the standard support patterns which were decided during the design phases used be insisted for the whole excavation phases in spite of the various geological conditions. When $\bigcirc$$\bigcirc$ tunnel was excavated up to 25m long, the severe displacement was generated in the Portal area of $\bigcirc$$\bigcirc$ tunnel and the tunnel face was pally collapsed. Therefore, this paper present the case study on construction associated with the Umbrella Arch Method used in silty ground by the NATM.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.153-160
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• 2006

Tunnel type spillway is rarely constructed in worldwide, and designed secondary in Korea. In this paper we pronounce a case study of tunnel type spillway design. We firstly considered lining concrete abrasiveness and cavitations for tunnel safety. This paper describes the design of tunnel type spillway section, excavation method, blasting, support and concrete lining.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.118-125
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• 1992

The ground deformation due to the tunnel excavation is dependent on various factors such as ground condition, geometry of the tunnel, excavation method, installation of support members, construction condition of each excavation stage, etc. And the distance from the facing effects significantly the stress conditions of the supported and unsupported ground due to the 3-dimensional structural nature of the excavated tunnel. The concept of ground characteristic line has been applied to properly consider the loading condition given by staged tunnel excavation so that the imaginary supporting pressure is applied against the surface of excavated ground. Discussions on the results of the performed finite element analysis were mainly made with respect to the ground settlement, tunnel displacement, earth pressure, stress mobilized in supporting members.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.221-228
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• 2002

The stability of a tunnel face is one of the most important factors in tunnel excavation. Especially, if a tunnel is located under groundwater level, groundwater may flow into the tunnel face and seepage forces acting on the tunnel face due to groundwater flow may affect seriously the stability of the tunnel face. Therefore, the seepage pressure at the tunnel face should be considered fir the proper design and safe construction of a tunnel. In this paper, the effect of tunnel advance rate on the seepage forces acting on the tunnel face was studied. The finite element program to analyze the groundwater flow around a tunnel with the consideration of tunnel advance rate was developed. Using the program, the parametric study for the effect of the tunnel advance rate and hydraulic characteristics of the ground on the seepage forces acting on the tunnel face was made. From this study, it was concluded that the tunnel advance rate must betaken into consideration as an additional parameter to assess the seepage forces at the tunnel face and a rational design methodology fer the assessment of support pressures required for maintaining the stability of the tunnel face was suggested for undetwater tunnels.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.10a
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• pp.231-237
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• 2001

This paper presents some proposed methods for discontinuum analysis with rock discontinuities data acquisited in tunnel design stage. The limit equilibrium method for rock block sliding and falling proposed in this paper can consider the tunnel excavation and support stage, and, to the extent, the standard deviations and means of joint set orientation. Simple Distinct Elemet modelling methods are recommended in estimating the stability of tunnels in jointed rock masses. Because, the simple models are likely to show more consistent and clear than very complex model with finite joint length and joint deviation parameters.

• Geomechanics and Engineering
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• v.22 no.1
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• pp.11-23
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• 2020

In this study, a new analytical-numerical procedure is developed to give the stresses and strains around a circular tunnel in rock masses exhibiting different stress-strain behavior. The calculation starts from the tunnel wall and continues toward the unknown elastic-plastic boundary by a finite difference method in the annular discretized plastic zone. From the known stresses in the tunnel boundary, the strains are calculated using the elastic-plastic stiffness matrix in which three dimensional Hoek-Brown failure criterion (Jiang and Zhao 2015) and Mohr-Coulomb potential function with proper dilation angle (i.e., non-associated flow rule) are employed in terms of stress invariants. The illustrative examples give ground response curve and show correctness of the proposed approach. Finally, from the results of a great number of analyses, a simple relationship is presented to find out the closure of circular tunnel in terms of rock mass strength and tunnel depth. It can be valuable for the preliminary decision of tunnel support and for prediction of tunnel problems.