• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.10a
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• pp.174-179
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• 1992

In this paper a discussion is presented about excavation responses of underground openings for radioactive waste disposal. The effects of excavation methods, stress redistribution, thermal change, and backfill materials are reviewed. Comparisons of computational models for discontinuous reek masses and discussions on numerical simulation techniques for the excavation of underground openings are also described. Finally, the application of the CAD system to the planning, design and construction of underground openings fop radioactive waste disposal is introduced.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.20-25
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• 1991

In order to predict properly the effects of ground motion associated wi th earthquakes on underground radioactive waste disposal facilities, understanding of the structural behavior of an underground opening in discontinuous rook masses subjected to dynamic loadings is essential. Therefore, this paper includes literature review on computational models for discontinuous rook masses and on mathematical models for the structural analysis of underground openings. Then, structural analyses of underground openings using the distinct element computer program written for the static and dynamic analysis of discontinuous rook masses have been performed.

• Geotechnical Engineering
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• v.14 no.1
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• pp.93-108
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• 1998

In this study, the analytic solutions and numerical methods were used to estimate the shape and size effects on the stability of underground openings. The stability of underground openings was evaluated by scrutinizing the effects of the rock mass quality, the state of in-situ stresses and the lateral earth pressure coefficient on the displacement, the stress concentration and the plastic region developed in the vicinity of the openings. The analytic solutions have shown that the stress concentration factor is inversely proportional to the radius of curvature of openings. Through parametric study on the various shapes and sizes of underground openings the characteristics of the controlling factors concerned with the stability were analyzed. Then, the study was extended to the horseshoe-shaped openings commonly used for under ground storage. Through the extended study the effects of the stress ratio and the height-towidth ratio of openings on the maximum displacement and plastic region developed around the openings were estimated. The results have shorn that the height-to-width ratio of domestic storage caverns can be increased economically without stability problem, as far as the lateral earth pressure coefficient is appropriate.

• KIEAE Journal
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• v.2 no.2
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• pp.39-44
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• 2002

Recently, underground spaces can be usually applied to the alternative of land use for parking. However, lack of window and natural light are among the most cited drawbacks associated with dark image of underground. If underground parking lots are designed to be positive and safe environment for people, openings for daylighting will play a significant role. The natural light and unobstructed view to outdoor are main elements to create optimal underground parking lots. This paper focuses on investigating the actual day lighting conditions and evaluating the day lighting performance of openings as potential lighting resources. For the study, the field measurements and Questionnaire surveys are conducted. And then, the day lighting performance of underground parking lots based on opening geometry and orientation are evaluated by scaled model experiments. As results, the feelings of safety and orientation of underground parking lots are improved by openings for day lighting regardless of the sizes. The required illuminances (daylight factor 0.5%) for underground parking lots can be satisfied in the skylight opening ratio of 4% or more.

• Tunnel and Underground Space
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• v.6 no.1
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• pp.10-18
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• 1996

Arched openings are generally excavated in underground construction works. Since stress distribution around openings depends on geological structure in rock mass, any shape of arched openings fully conformed with in-situ stress condition should be recommended to maintain mechanical safety of structures. Shape of arched openings is specified by both roof curvature and height-width ratio, and especially this report presents deformation behaviors related with roof curvature. Scale model tests and numerical studies of various shaped openings are conducted, where rectangular opening shows the greatest convergence. Through the anlayses of various arched opengings, as radius of roof curvature is increased, roof lowering and sidewall closure are remarkably increased, whereas floor heaving is increased little by little. By the way, it is useful that displacements of openings are roughly estimated in the stage of preliminary investigation. To find out elastic displacements of arched openings with any roof curvature, regressional formula and charts by least square method are represented. In addition elastoplastic deformation behavoirs of arched openings concerning associated adn non-associated flow rule are discussed.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2004.04a
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• pp.219-229
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• 2004

In this article a comprehensive review of the Rock Mass Rating and Q-rockmass classification systems is made with reference to their scope with in the constraints of underground mining operations. The modifications suggested by KIGAM for both the RMR and Q for the calculation of a safe unsupported span were tested for Daesung and Pyunghae underground limestone mines. Even though the suggested modifications were site specific, the additional parameters considered in the above classification systems are very significant for a design of stable underground openings, considering any general mining conditions.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.369-377
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• 2005

The stability of underground openings is a major concern for the safety and productivity of mining operations. Rock mass classification methods provide the basis of many empirical design methods as well as a basis for numerical analysis. Of the many factors which influence the stability of openings, the span of the opening for a given rock mass condition provides an important parameter of design. In this paper, the critical span curves proposed by Lang, the Mathews stability graph method and the modified critical span curve suggested by the authors have been assessed. The modified critical span curve was proposed by using Mathews stability graph method. The modified critical span curve by the author have been used to assess the stability of underground openings in several limestone mines.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.111-117
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• 1992

In order to design and construct a safe and economic underground structure, it is essential to understand the structural behavior of underground openings considering the effect of the sequential excavation. Therefore, this paper includes the study of initial stress distribution before excavation and stress redistribution due to the sequential excavation. And discussion on numerical simulation techniques for the sequential excavation is also included. Then, the underground structure is analyzed using the finite element and distinct element methods of analysis considering the effect of the sequential excavation. Based on the results of the analysis, the followings are discussed: shape of the openings, effect and timing of structural reinforcements. methods and sequence of excavation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.281-288
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• 2000

Three-dimensional dynamic analysis of underground openings subjected to explosive loadings considering the effects of water saturation is carried out in this study. The problem considered in this study is an unlined circular tunnel subjected to a finite cylindrical charge placed at the center of the proposed tunnel. The surrounding rock mass is assumed to be the limestone with 13.5% of porosity. Two calculations are compared using an identical explosive charge; the first in dry rock of 13.5% porosity, the second in the identical rock, but in a fully saturated condition. It is shown that underground openings in saturated porous medium could be significantly more vulnerable to the potential damages associated with high motions and shear failure than those in dry medium.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.457-475
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• 2018

For increase of reality in numerical analysis, a blasting vibration waveform obtained from field blast operations has been directly used for input parameters of dynamic analysis in the form of vibration velocity. A numerical model was built considering the geological characteristics of underground limestone opening as well as the mining stages in this opening, and the effect of blast operations on stability of underground limestone opening was investigated by dynamic numerical analysis. The adequacy of applying the real vibration waveform to dynamic analysis has been approved from the preliminary analysis, and the dynamic numerical analysis results show that the continuous mining operation can cause the collapse of roof in openings and the active yield zone around openings. Therefore, the additional reinforcements should be applied for ensuring the stability of underground limestone openings.