• Geotechnical Engineering
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• v.13 no.6
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• pp.107-122
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• 1997

This paper presents a ground surface settlement prediction method for shield tunneling in cohesive soils. In order to develop the method, a parametric study on shield tunneling was performed by using a threetimensional elasto-plastic finite element analysis, which can simulate the construction procedure. By using the results of the finite element analysis, the ground movement mechanism was investigated and a base which relates the ground surface settlement and iuluencing factors was formed. The data base was then used to formulate semi -empirical equations for both surface settlement ratio above tunnel face and imflection point by means of a regression analysis. Furthermore, a prediction method for transverse and longitudinal surface settlement profiles was suggested by using the leveloped equations in conjunction with the normal probability curve. Effectiveness of the developed method was illustrated by comparing settlement profiles obtained by using the developed method with the results of finite element analysis and measured data. Based on the comparison, it was concluded that the developed method can be effectively rosed for practical applications at least within the conditions investigated.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.10-19
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• 2008

Most of flooding cases in tunnels are associated with huge inrushes of water due to the fracture zone with very high water head. To find out the causes and countermeasures for flooding cases, a dozen of tunneling cases are studied. Case studies presented here show that if the flooding had been forecasted and pre-drained prior to the tunnel excavation, such accidents could have been prevented. From this observation, we suggest a new horizontal drainage system with pre-investigation and pre-drainage concept. Seepage analyses are performed to analyze the water head reduction effect on the tunnel face by drainage pipes during the construction of subsea tunnels. Drainage system analyses are performed to analyze performance of the drainage system. These analysis results show that the suggested horizontal pre-drainage system provides a clear drainage and water head reducing effect. Finally, the proposed system can be a new alternative to the present water controlling methods applied to subsea tunnels.

• Journal of the Korean Geotechnical Society
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• v.23 no.5
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• pp.153-162
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• 2007

For the reinforced earth wall constructed on a soft ground in parallel with replacing soft soils, the behavior of the wall according to variations of thickness and stiffness of soft layer, replacement depth, and wall height is investigated using a finite element method, in which incremental construction steps including consolidation of soft soil layer are considered. The behavior of wall is characterized by investigating displacements and settlements developing at the wall, and shear strains developing in a soil deposit. The stability of wall is, then, evaluated by comparing these values with the safety criteria determined on the basis of the literature. Based on the investigation, it is shown that the behavior of wall is influenced naturally from soft soil thickness(t), replacement depth(d) and wall height(h), but more significantly from d and h. In addition, it is also shown that the normalized replacement depth, d/h, required for the safety of wall is not influenced significantly by the variations of t and h. Consequently, it can be concluded that the proper replacement depth can be suggested in an equivalent value in terms of d/h, even for the cases where the wall height is varying with stations, but the variation is not significant.

• Journal of the Korean Geotechnical Society
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• v.26 no.8
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• pp.39-47
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• 2010

In recent days, the foundations of huge structures in general and mega foundations of grand bridges and high-rise buildings in particular are required in geotechnical engineering. This study described 3 dimensional behavior of mat foundation on soft rock based on a numerical study using 3D finite element method. A series of numerical analyses were performed for various soil conditions and mat rigidities under vertical loading. Based on the results of the parametric study, it is shown that the prediction of the settlement, cross sectional tensile stress and bending moments in the mat is overestimated in the analysis without considering interface behavior in comparison with the analysis considering interface between mat and rock mass.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.20 no.3
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• pp.243-253
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• 2002

These days, the application range of digital photogrammetry is being extended actively, so the great variety of research is being progressed about improvement of measurement accuracy. This method can acquisite a high analysis accuracy and can acquisite easily image. But, So this method require a much processing time and effort by increasing a data amount, as the automation of processing must be completed for efficiency improvement of processing. In this study, the automation of image processing stage is established for multi-image aquisition and analysis about a radio telescope. Also, the precise measurement and the accuracy on object were intended to be improved. As a result of this study, the accuracy on the object which demands precise measurement was enhanced from multi image analysis, and also the assembly accuracy of the object could be checked by precise measurement and curve fitting.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.192-203
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• 2009

In the new Seoul-Busan high speed railroad construction specially in area of city center passage the roadbed establishment is recommended the staibility for the existing subway tunnel segments of Busan subway 1st and 2nd lines regarding the appearance condition, a quality condition and the durability of the objective facility, and it evaluates the numerical analysis using MIDAS/GTS which leads the stability of the objective facility and investigatesd tunnels. 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 Method. Based on the results the interaction mechanism between the tunnelling and groundwater is identified. In the both of 1st and 2nd Line the maximum sinkage, unequal sinkage and the lining stress from numerical analysis are within permission and the damage degree is appearing to be disregarded. But it enforces necessary Pre-grouting in order to minimize an actual tunnel face conduct and when the tunnel is excavated it is also necessary to minimize the outflow possibility.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.229-242
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• 2009

Numerical analysis has been performed to estimate maximum settlement, maximum horizontal displacement and total settlement volume at the ground surface due to tunnel excavation varying ground condition, tunnel depth and diameter, and construction condition (volume loss at excavation face). The maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering ground condition, tunnel depth and diameter, and construction condition, and it has been also compared with the maximum horizontal displacement. In addition, the volume loss ($V_L$) at tunnel excavation face has been compared with the total surface settlement volume ($V_s$) with the variation of ground condition, tunnel depth, and tunnel diameter. The results from the numerical analysis have been compared with field measurements to confirm the applicability and validity of the results and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the ground movements due to tunnel excavation.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.310-320
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• 2012

This paper describes the design and construction of a 2-arch tunnel with varying section. This new design has advantages of 2-arch tunnels, which is rather expensive, but is still economically competitive compared to parallel tunnels. Economic analysis was also conducted. To secure the stability of the varying section tunnel, excavated part was reinforced by tie-bolts and RRS, and 2-arch part was supported by EPS blocks and concrete walls. Stability of the pillar was theoretically analyzed and also examined by numerical simulations for various widths. Displacement monitoring was conducted and results were compared with numerical results. Economic analysis showed reductions in construction cost and period by 11% and 10 months respectively.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.35-48
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• 2009

An excessive ground displacement occurs with excavating tunnel in a fault zone because the fault has properties of soft ground in generally. It may have had a bad influence to adjacent structure. So, rapid reduction of ground strength by groundwater inflow should be prevented. It must be established for an impervious and reinforcing effect of ground to ensure a tunnel stability. The ground settlement and reinforcing effects were estimated by numerical analyses on tunnel through 570 m sector in Yangsan fault zone of Keongbu high-speed railway. Settlements evaluated by numerical analysis is similar to those calculated by using equation of Loganathan & Poulo. It was shown that reliable estimate of ground settlement by applying a prediction equation is possible. Applicability of adopted tunnel reinforcement method in fault zone was investigated by results of pilot construction and numerical analysis. Results from this study indicate that the adopted reinforcement method make tunnel displacements and member stresses restrain in design criteria.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.271-277
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• 2000

쉴드터널 공법은 도시의 지하철도, 상ㆍ하수도, 전기ㆍ통신 등을 설치하기 위한 터널 건설 수단으로 활용되고 있다. 일본은 1960년경부터 도시의 근대화를 추진하면서 infrastructure를 정비하였으며 이에 따라 쉴드터널 공법의 적용이 급속히 증대하였다. 도시의 지하에 터널을 건설함에 있어 가장 중요한 것은 기존 도시구조물에 대한 영향을 최소로 줄여서 도시기능을 보전하는데 있다.(중략)