• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.589-604
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• 2021

Waterjets for rocks have various advantages of the non-contact and eco-friendly excavation using only water and abrasive. To overcome the problems (e.g., dust and noise occurrence) of the conventional drilling methods, waterjet excavation methods are broadly used. It is advantageous to operate a couple of nozzles in order to increase the waterjet excavation efficiency. When multiple nozzles are used, it is essential to analyze the excavation performance and shape according to the nozzle operation method. In this study, nozzle angle, horizontal distance between nozzles, and standoff distance were defined as nozzle operating parameters and the excavation performance and shape were analyzed. As a result of the experiment, when the nozzle angle and standoff distance are increased, the excavation depth is decreased and the effective depth tends to be increased. In addition, based on the experimental results, the excavation shape criteria required for nozzle insertion were proposed and optimal nozzle operating parameters were derived according to the criteria. This study result is expected to be used as useful basic research in the future development of multiple waterjet nozzles for rock drilling.

• Journal of the Korean Geosynthetics Society
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• v.7 no.3
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• pp.31-40
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• 2008

The deformation behavior of the excavated behind ground due to the displacement shape of retention walls is predicted by numerical analysis, which can be performed using the artificial displacement method with elasto-plastic constitutive model. The displacement shape of the behind ground around the retention wall is similar to the displacement shape of the retention wall. However, far from the retention wall, it changes to the displacement shape of cantilever. The deformation (the settlement, the lateral movement) of the excavated behind ground can be decreased by restraining the upper displacement of the retention wall. The displacement shape of the retention wall due to excavation affects on the plastic failure zone and decreasing zone of stability of the excavated behind ground.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.27-36
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• 2008

This paper analyzed the effects related to the difference of the geometrical shape of the ground excavation by comparing the displacements of the earth retaining wall of the strut resulting from the change of the excavation breadth B and the excavation length L, adopting the three dimensional FDM analysis. It appeared that the displacement of the earth retaining wall of the strut increases in accordance with the increase of L/B and it decreases as it becomes nearer from the center to the comer where the temporary structural system forms, and the wale member is closured because of the effects of the confining effect by the closure of the earth retaining wall and the wale member. This paper proposed a formula in which the results of three dimensional FDM analysis which considers the shape of the excavation plane can be obtained from those of two dimentional FDM analysis which does not consider the shape of the excavation plane. And the results of the formula were compared with those of the site instrumentation analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.3
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• pp.175-184
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• 2002

Ground reaction curve is very useful information for estimating the installation time of the tunnel support. The ground reaction curve can be estimated by analytical closed form solutions derived in case of circular section and isotropic stress condition. The nature of the ground reaction, however, depends significantly on tunnel configurations. Nevertheless, few purely analytical and experimental studies of this problem due to tunnel configurations appear to have been carried out. Therefore, it is necessary to investigate the influence of tunnel configurations in order to use simply in practical design. This paper describes a numerical study for the intial elastic displacement in the ground reaction curve due to configuration of tunnel excavation. In order to evaluate the applicability of analytical closed form solution in practical design, the parametric studies were carried out by numerical analysis in elastic tunnel behaviour. In the studies, S value, namely configuration factor, defined as the ratio between tunnel height (b) and width (a), varies between 0.5 and 3.0, initial ground vertical stress varies between 5~30 MPa for each S values. The results indicated that the self-supportability of ground is larger in the ground having low S value. It, however, is suggested that the applicability of closed form solution may not be adequate to determine directly the installation time of the support and self-supportability of ground. It should be necessary to perform the additional numerical analysis.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.261-277
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• 1999

The horizontal and vertical earth pressures in backfill space which is narrowly excavated like ditch are affected by the share of ditch backfill space and the wall friction between excavated surface and backfill soil. In this paper, for the excavated surface the Handy's equation of a symmetric vertical case and the Kellogg's equation of a symmetric sloped one are modified to show the minor principal stress arch for the unsymmetrical excavated backfill space. Compared with the soil test box result, a similarity in magnitude and distribution of backfill earth pressure shows that the earth pressure has been observed. The backfill earth pressure in unsymmetrically sloped space has been shown twice as much as the one in vertically excavated space and also remarkable decline of arching for the former case. It is verified that the earth pressure equation should account the shape and size of backfill space to calculate the earth pressure for similar structure to the one handled in this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.60-66
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• 2021

The core is extracted through drilling and used to evaluate the feasibility of developing mineral resources. To extract the core, a bit is installed in the forefront of the drilling device for drilling. Here, the drill bit receives stress due to direct friction against the ground. In addition, a bit appropriate for the given ground condition should be used due to the possibility of damaging a bit as a result of friction. This paper used a current bit model based on an impregnated bit and analyzed a new bit model that uses a stiffener of similar/disparate materials. The hardness and deflective strength were then evaluated by modeling the shape of impregnated bit through a calculation based on a theoretical formula. Through FEM analysis of the existing model and the new model, the stress and strain calculation results were optimized to minimize the stress and strain with a stress of 1.92 × 107 Pa and a strain of 9.6× 10-5 m/m.

• Geotechnical Engineering
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• v.12 no.5
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• pp.27-40
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• 1996

Box culvert has long since been used for various purposes , water and sewerage works, communication and electricity facilities, subway, railway, etc. In urban area, the construetion of box culvert generally consists of excavation-installation of the culvert-backfill. However, the existing design methods for earth pressure on the box culvert do not take into account the excavation(or backfill) geometry. ' A new method considering excavation geometry for earth pressure on box culvert is suggested here. The lateral earth pressures by the newly suggested method agree relatively with results of finite element analyses, but those of existing method are greatly overestimated. The vertical pressure on the top of the box culvert by the new method is similar to those of existing method and finite element analysis. However, the reactional pressure on the bottom of the box culvert depends largely upon the stiffness of the foundation soil. The reactional pressure by the new method agrees well with that of finite element analysis, only when the stiffness is low. From the finite element analysis it is shown that the lateral earth pressure on box culvert depends upon the excavated slope (G) and the net bottom distance (Bc).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.920-926
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• 2014

In this study, we applieorithmd the inverse analysis alg to the prediction of displacement shape in the example construction and verified the feasibility of suggested algorithm. For this purpose, as information processing knowledge in the field of IT is required and the need for convergence with the major is emerged, it is intended to try to apply the algorithm to the construction sector. Prediction of displacement shape is very important since it is related to the earth pressure of slurry wall and effecting on the safety of slurry wall after anchor removal. 3 levels of inverse analysis were applied to the slurry walls in 3 sites and compared the measured displacement shape with predicted displacement shape of the last excavation construction. As the predicted displacement shape was matched well with the measured one, the applied analysis algorithm in this study can be applied to the excavation construction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.83-97
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• 2018

Tunnels are widely used for special purposes including roads, railways and culvert for power transmission, etc. Its cross-section shape is determined by uses, ground condition, environmental or economic factor. Many papers with respect to behaviours of adjacent ground and existing structure tunnelling-induced have been published by many researchers, but tunnel cross-section have rarely been considered. A collapse of tunnel causes vaster human and property damage than structures on the ground. Thus, it is very important to understand and analyse the relationship between behavoiurs of ground and cross-section type of tunnel. In this study, the behaviour of ground due to tunnel excavation for underground station below the grouped pile supported existing structure was analysed through laboratory model test using a trap-door device. Not only two cross-section types, 2-arch and box, as station for tunnel, but also, offset between tunnel and grouped pile centre (0.1B, 0.25B, 0.4B) are considered as variable of this study. In order to measure underground deformation tunnelling-induced, Close Range Photogrammetry technique was applied with laboratory model test, and results are compared to numerical analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.622-640
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• 2009

원유 비축기지 저장공동과 같이 상하로 긴 형상의 대규모 공동에서 횡방향의 지압이 과도하게 작용하면 천정부의 응력집중과 측벽의 암반 변위가 과도하게 발생하여 저장공동의 불안정 요인이 된다. 특히 지압의 절대 크기가 암반 강도의 일정 비율 이상이 되면 응력 집중에 의한 암반의 취성 파괴를 유발하고, 이러한 현상은 터널 굴착 시 발생하는 파괴음(popping)과, 굴착면에 평행한 형태로 암편이 탈락하는 취성파괴(spalling) 현상을 동반한다. 이 글에서는 대규모 지하저장공동 굴착시 실제 발생한 과지압으로 인한 문제 사례에 대해 소개한다. 저장공동 굴착시 관찰된 암편 및 숏크리트 탈락과 균열 발생 현상을 관찰하고 암반 계측결과 분석을 통해 과지압의 현상을 진단하였다. 과지압 구간의 현재 상태 및 원안 설계안에 대해 연속체 및 불연속체 안정성 해석을 실시하여 문제의 심각성을 평가하였다. 이를 통해 굴착 형상 변경 및 특수 보강 방안을 제안하였으며 제안된 안의 보강효과에 대한 수치해석 평가 결과를 재검토 하였다. 이들 결과를 종합하여 과지압구간 보강안을 도출하였으며 상시 안정성 감시 대책으로 현장 암반의 미소파괴음 계측 방안을 제시하였다.