• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.4
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• pp.305-311
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• 2005

Shotcrete adhesive strength in large section tunnels in jointed rock masses plays an important role in preventing rock block from falling and shotcrete debonding due to blasting vibration. Nevertheless, it has not been considered as a major factor such as shotcrete compressive strength in design and construction. For this reason, the purpose of this study is to analyze the effect on shotcrete adhesive strength for large-sectioned tunnels. First, the parametric study using numerical model similar to Holmgren's punch-loaded test was executed for various range of adhesive strength. It shows that the shotcrete bearing capacity is linearly proportioned to the adhesive strength between shotcrete layer and blocks. And then, distinct element analysis of a jointed rock tunnel for an adhesive strength of 1 MPa and a conventional fully-bonded condition between the shotcrete layer and the excavation face was compared in order to evaluate the effect of the shotcrete adhesive strength.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.241-250
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• 2003

Rock mass is very inhomogeneous in nature and data obtained by site investigations and tests are very limited. For this reason, many uncertainties are to be included in the process of constructing structures in rock mass. In the design of a tunnel, support pattern, advance rate, and excavation method, which are important design parameters, must be determined to be optimal. However, it is not easy to determine those parameters. Moreover if those parameters are determined incorrectly, unexpected risk occurs such as decrease in the stability of a tunnel or economic loss due to the excessive supports etc. In this study, how to determine an optimal support pattern and advance rate, which are the important tunnel design parameters, is introduced based on a risk analysis. It can be confirmed quantitatively that the more supported a tunnel is, the larger reliability index becomes and the more stable the tunnel becomes. Also an optimal support pattern and advance rate can be determined quantitatively by performing a risk analysis considering construction cost and the cost of loss which can be occurred due to the collapse of a tunnel.

• Journal of the Korean Society of Costume
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• v.65 no.7
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• pp.47-59
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• 2015

This paper studies the conservation treatment of Lady Shim's costume, which was excavated in Jecheon Province in 2012. There were the significant problems, which were encountered in the treatment of the costume ; First the Jeogoris were transformed during the excavation, Second fibers were seriously deteriorated, Third most of the fabrics such as Chusa were readily deformed. To overcome these problems and to secure stability in the conservation treatment, we decided to alternate between two different washing methods ; dry cleaning by n-hexane and wet cleaning by water. The costume shape was recovered by steaming and by swelling with Hanji(Korean traditional paper). The combined cleaning method proved to be relatively efficient and stable. In addition, the shape of Chusa was well preserved by dry cleaning.(using n-hexane also solved the problem of bad smell after washing with organic solvents.) The effects of the conservation treatment on the excavated costumes could be seen in the change of Lab color difference. Washing made the distribution of Lab color difference narrower, which may suggest that the impurities on the fiber was removed by washing. In addition, the value of L was greater than a-value and b-value after the treatment. This result indicates that the change of value represents the change of color difference by cleaning.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.1
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• pp.63-72
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• 2005

The influence of internal water pressure under the Probable Maximum Flood (PMF) on tunnel spillway is analysed using 3D FDM analysis. HEC-RAS program including 1-D hydrologic numerical model was also implemented to estimate the maximum pressure on the lining under the PMF, thereafter determined rational internal water pressure. Tunnel spillway was designed as twin tunnel and excavation and supporting stage are fully considered. Analysis was classified into the 3 cases; pressure is applied only to the left tunnel, only to right tunnel, and to both tunnels. The maximum tensile stress and axial force in supporting materials induced by water flow were compared with the critical values to assess the stablilty of the tunnel and the locations of stress concentration parts were also examined.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.77-86
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• 2003

The finite element method and statistics of the convergence measurement are useful method of the stability analysis of the tunnel adjacent to the pier. It is the purpose of the this case study to certificate of validity of the application of those methods. The safety of the pilot tunnel method and LW pre-grouting has been evaluated from the FEM analysis. The three-dimensional finite element method is carried out for the decision of the level of stress redistribution at the two-dimensional numerical analysis. An analysis of the convergence is carried out by the estimation of preceding convergence at tunnel excavation. F-examination is applied for this estimation. As results of that analysis, The F-value is from 10.81 to 158.74 and the coefficient of determination is from 0.82 to 0.99. An analysis of convergence is carried out by using regression analysis. Consequently, it is shown that the convergence can be modeled as following function C(t)=a[1-exp(-bt)].

• Tunnel and Underground Space
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• v.27 no.4
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• pp.195-204
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• 2017

This case study introduces the construction of large cross section tunnel for underground ventilation system in Sillim-Bongcheon Tunnel Project. In order to grant the safety and efficiency in connecting the ventilation shaft (7.8 m of width, and 6.6 m of height) to a tunnel for axial fan facility (20.8 m of width, and 12.3 m of height), gradual enlargement of tunnel cross section was employed between those and temporary support method was determined based on Q system. In addition, some original designs were revised during construction stage to improve the efficiency of excavation in large cross section tunnel. The advance length was optimized and top heading of the tunnel was excavated without partition in accordance with ground condition and numerical stability analysis results. It is believed that some experiences and considerations in this case study will be useful for the future design and construction in similar large cross section tunnel such as large underground ventilation system or road tunnel with four lanes.

• Explosives and Blasting
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• v.27 no.1
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• pp.47-52
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• 2009

Blasting is necessary for excavation processes since more than 70% of korean land is consist of mountains. The vibration and noise accompanied by blasting processes usually bring about public complaints. Blasting patterns are chosen by economical efficiency, stability and construction conveniency. However, there are many alternatives without control to settle the popular complaint. To prevent those alternatives, standard blasting method for design and construction were suggested by MLTM (Ministry of Land, Transport and Maritime Affairs) in 2006. However, standard blasting pattern of MLTM was designed in a lump irrespective of types of rocks. Economical loss may occur by ignoring the characteristics of rocks for the applications to the rocks with low intensity, such as shale, or containing many joint. We deduced some economical progresses by performing test blasting with adjusted drilling spacing and length of burden considering the characteristics of local rock. This paper suggests the start of case studies for different applications. Economic improvement can be expected by applying those results deduced from case studies to design and construction.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.29-36
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• 2008

The shotcrete is a NATM technique as a major tunnel support for ground stability after tunnel excavation. Instead of a general concrete lining method, it is a trend for curtail of construction periods and reduction of construction expenses that required to use of the permanent shotcrete lining. This high-strength shotcrete is required to use as a permanent shotcrete lining. This brought out the solution of environmental pollution and harmfulness to human. Accordingly, in this study specimens for strength measurement were made to develop shotcrete possible to develop materials in early with cement mineral accelerator as NATM method construction. It was compared with existing shotcrete material, unconfined compression test, flexural strength test, antiwashout underwater test were experimented. The fish poison test was experimented to evaluate an influence of environment. As a results of the test, unconfined compressive strength and flexural strength were equivalent with 28-curing day strength of existing material. An antiwashout of research subject material was revealed excellently in antiwashout Underwater test. As a results of the fish poison, an evaluation research subject material was founded more environmentally friendly than existing shotcrete.

• Journal of the Korean GEO-environmental Society
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• v.11 no.3
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• pp.53-62
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• 2010

In the early 1990s, it was first introduced the soil nailing method for the slope stability and ground excavation and widely used as method of reinforcement. Also the application of soil nailing has been improved and developed. Most recently used for grout soil nailing greatly improve the methods and techniques for self-improvement techniques are classified as soil nailing. As the representative for the grout pressure method to improve the join method pressure grouting and improved method for the self-drilled soil nailing, removable soil nailing, extension grout method. Three dimensional finite difference analysis was used to evaluate characteristics of pull-out behavior of extension grout method. In this paper, it was described a characteristics of pull-out behavior of soil nailing with extension grout method through the result of numerical method.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.869-887
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• 2008

Coffer dam for tunnel type spillway in inflow section of Dae-am dam was originally planned as 2 lines sheet piles with Water Zet method. But, the result of pilot test was caused of some problems that vibration during installation of pile could pollute water and water leakage could the lower part. So, sheet piles was not satisfactory for faculty of coffer dam. Structural instability of sheet pile system need to reinforcement. Characteristic of Dae-am dam was small reservoir capacity but wide drainage area, of which it was judgment that security of leakage and stability was difficult during excavation of inlet part. So, we consider that water curtain method utilized with in site pouring concrete pile method was designed at weir part of spillway. We were known about basement rock that geological boring was carried out in weir part. After taking a deep consideration, PRD method was accepted as a new method. Concrete pile by PRD was installed to below country rock. CJM method was carried out with PRD. After making concrete wall using Top-down method, earth anchors were installed for supporting it. According to the result of numerical analysis, as water level rises, wall is stable.