• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.303-314
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• 2004

This study is intended to investigate the geotechnical behavior of jointed mass on tunnel excavation experimentally. Laboratory test were conducted in various conditions of distance from joint to tunnel and in-situ stress ratio ($K_0$). In case, the ground around the tunnel that has the joint angle $90^{\circ}$ generate the greatest influence in crown and far shoulder from joint. If the in-situ stress ratio is low, tangential stress of side wall that is opposite side of the joint is increased more than in crown. Otherwise in case, joint angle $45^{\circ}$, the generated compress stress is found out that left side of the tunnel of near the joint has influence on stability of the tunnel about 3 times than non-jointed rock.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.771-785
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• 2016

The thermal conductivity of soils is an important property in energy-related geotechnical structures, such as underground heat pumps and underground electric power cable tunnels. This study explores the effects of geotechnical engineering properties on the thermal conductivity of soils. The thermal conductivities of quartz sands and Korean weathered silty sands were documented via a series of laboratory experiments, and its variations with effective stress, porosity, and water saturation were examined. While thermal conductivity was found to increase with an increase in the effective stress and water saturation and with a decrease in porosity, replacing air by water in pores the most predominantly enhanced the thermal conductivity by almost one order of magnitude. In addition, we have suggested an improved model for thermal conductivity prediction, based on water saturation, dry thermal conductivity, saturated thermal conductivity, and a fitting parameter that represents the curvature of the thermal conductivity-water saturation relation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.84-92
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• 2010

This paper presents the influence of the underground structure (such as cavern and tunnels) behavior according to the rock joint orientation and underground cavern size. In order to perform this research, numerical and experimental studies are carried out. Stress aspect was assessed by quantitative according two kind of factor. In the experimental study, the laboratory model tests are performed in the several ground conditions with different underground cavern size. The results obtained from the model tests are also verified and evaluated using the numerical analysis. Due to the underground cavern, it is found from this study that the stresses developed in archcrown, side wall of underground are increased with increasing the underground cavern size. It is also investigated that the rock joint direction is one of main influence factor as risk factor, to maintain the underground cavern stability. It may be expected that this research will provide the very useful information to evaluate the underground cavern stability.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.3
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• pp.367-372
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• 1997

Excessive water stress is one of major limiting factors affecting soybean yield, especially when soybean is grown in converted upland from paddy field. The present study was undertaken to know the genotypic variation in yield response of soybean to different environments in combination with soil texture and underground water table depth. Eight recommended soybean varieties in Korea and two supernodulating soybean mutants introduced from USA were planted in the lysimeter which was filled with two different soil types(sandy loam and clay loam). Of three underground water table depths(10, 30, and 50 cm) during whole growth stage, the lowest 10 cm was included to create excessive water stress. Yield was significantly different according to the underground water table depth and soybean genotypes, whereas soil type did not affect yield. There were significant interaction effects of soybean yield among soil type, soybean genotype, and underground water table depth. Yield of nts 1116 showed the highest across environments. Based on the regression analysis, the most stable variety was Sobaeknamulkong(bi=1.09). Jangsukong was fairly stable and high in yield, when compared to other soybean genotypes. However, nts 1116 was the most desirable ($D_i=228$) mainly due to the highest yield rather than the greater stability over environments. Multiple regression analysis revealed that shoot dry weight and nodule number were major factors affecting yield in the combined data over three water table depths and two soil types.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.137-140
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• 2006

As underground construction is a large component of the cost of construction and a term of works in Top-Down construction, it is important to reduce the term of works in underground construction. The purpose of this study is to analyse buckling stress and load of prefounded columns as the process of excavation is changed, and propose a suitable process of excavation to increase the speed of works. When several floors are excavated, the valid buckling length of profounded column is increase and allowable buckling stress is decreased. The result shows that all columns are safe in buckling down to B3th story whether 2 stories or 3 stories are excavated straightly. However, several columns are not safe from B4th story when 2 or 3 stories are excavated straightly. With these results, a process can be designed that first B3 stories are excavated straightly, and then excavate B4th story putting concrete on B1st and B2nd story.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.4
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• pp.485-492
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• 2007

In this study, based on the temperature distribution and the spalling histories those obtained in the companion paper, the thermal stress and moments of underground box structure were estimated. Additionally, the ultimate sectional moment considering with the thermal nonlinearities of material were estimated and the load carrying capacity of underground box structure was also obtained. As results, the load carrying capacity of negative moment part was dominated by thermal moment that come from thermal gradient of the section. However, the load carrying capacity of the positive moment part was rules by the yield stress of rebar that exposed to the high temperature induced spalling phenomena.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.2
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• pp.145-153
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• 2020

The purpose of this study is to investigate the effects of composition of underground structural wall and H-pile in soil cement. The results of previous experimental studies are re-analyzed and the nonlinear cross-sectional analyses of composite basement walls are performed to verify their nonlinear flexural behavior. Based on the study, it is explained how the gap deformation between H-Pile and RC wall should be considered in the design of flexure of composite underground walls. The nonlinear cross-sectional analysis shows that the load-displacement curves of composite basement wall specimens exhibiting flexural behavior exist between the results of the analysis of the complete and non-composite cases. When predicting the behavior of the composite basement wall by nonlinear cross-sectional analysis, the flexural behavior of the composite basement wall could be suitably predicted by considering the reduction of the composite ratio due to tensile stress acting on shear connectors.

• Tunnel and Underground Space
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• v.9 no.3
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• pp.194-203
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• 1999

The axial stress in rock bolt, the shear stress at the bolt-grout interface and the neutral point are analyzed to understand the mechanical behavior of rook bolt. To analyze the support effects of rock bolt in various geological conditions, numerical analyses are performed with regard to bolt spacing and bolt length in several geological conditions and tunnel sizes. Through the numerical analyses, the distributions of maximum tensile stress and shear stress are determined. And the excavation width of underground opening affects the position of the neutral point. In the circular opening supported by pattern bolting, the increase of confining pressure, the reduction of plastic zone, and that of ground displacement are determined by using the radial stress increase ratio, the plastic zone reduction ratio and the displacement reduction ratio respectively. The results of this study can be applied to a practical tunnel design through understanding of the trends of these support effects.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.471-480
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• 2002

In this paper, the thermal stress analysis of spent nuclear fuel disposal canister in a deep repository at 500 m underground is carried out for the basic design of the canister. Since the nuclear fuel disposal usually emits much heat, a long term safe repository at a deep bedrock is used. Under this situation, the canister experiences the thermal load due to the heat generation of spent nuclear fuels in the basket. Hence, in this paper the thermal stress analysis is executed using the finite element method. The finite clement code Eot the analysis Is not written directly, but a commercial code, NISA, is used because of the complexity of the structure and the large number of elements required for the analysis. The analysis result shows that even though the thermal stress is added to the stress generated by the hydrostatic underground water pressure and the swelling pressure of the bentonite buffer, the total stress is still smaller than the yield stress of the cast iron. Hence, the canister is still structurally safe when the thermal loads we included in the external loads applied on the canister.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.10a
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• pp.3-16
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• 2008

The underground construction and mining are facing many geomechanics challenges stemming from, geological complexities and stress-driven rock mass degradation processes. Brittle failing rock at depth poses unique problems as stress-driven failure processes often dominate the tunnel behaviour. Such failure processes can lead to shallow unravelling or strainbursting modes of instability that cause difficult conditions for tunnel contractors. This keynote address focuses on the challenge of anticipating the actual behaviour of brittle rocks in laboratory testing, for empirical rock mass strength estimation, and by back-analysis of field observations. This paper summarizes lessons learned during the construction of deep Alpine tunnels and highlights implications that are of practical importance with respect to constructability. It builds on a recent presentation made at the $1^{st}$ Southern Hemisphere International Rock Mechanics Symposium held in Perth, Australia, in September this year, and includes results from recent developments.