• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.17-28
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• 2006

Structural health monitoring is important to maintain the safety and serviceability of the structures. The displacement in the structure should be precisely and frequently monitored because it is a direct assessment index indicating its stiffness. However, no practical method has been developed to monitor such displacement precisely, particularly for high-rise buildings and long span bridges because they cannot be easily accessible. To overcome such difficult accessibility, we propose to use a LIDAR system that remotely samples the surface of an object using laser pulses and generates the coordinates of numerous points on the surface. In this study, using terrestrial LiDAR, we develop a novel displacement measuring model for structural health monitoring and perform an indoor experiment to prove its performance.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.91-100
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• 2002

This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

• Journal of the Korean Geosynthetics Society
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• v.12 no.2
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• pp.55-66
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• 2013

The experiment of model soil structures has been executed for the soil retaining wall in various conditions of excavation, in this study, to analyze the behavior of the corner of opening. The ground for experiment has been constituted with the sandy soil of relatively loose density, the construction condition has been divided into the opening length of corner, embedded depth, existence of strut, etc., and the excavation has been carried out for 4 stages in total. The behavior characteristics at the corner of opening area has been verified by concentrate analysis of the displacement of wall and the subsidence of ground surface, for each construction and excavation condition, using the measuring instrument mounted inside the model soil structure. In the result of experiment, it has been analyzed that the opening area of corner is unstable structurally compared to the linear area, as it shows that the wall displacement and subsidence of ground surface have been increased when the opening length of corner gets longer. The longer the embedded depth, ground surface settlement of coner was decreased 40%. To apply deeper embedded depth than designed estimate was an advantage in the safety. As a result of the analysis of coner behavior with added struts, maximum surface settlement and maximum horizontal displacement was evaluated 40% and 30%, respectively. Hence increased embedded depth with the added struts in coner edge was effective in the safety.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.34-34
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• 2011

본 논문에서는 반도체의 제조공정 중 작동되는 건식 전공펌프에서 측정한 다중변수들의 통계적, 물리적 특성을 소개한다. 흡기부 및 배기부 압력과 부스터/드라이펌프의 소비전류와 같은 상태변수의 변위 분포는 2개 이상의 특징적인 구간으로 나뉘는 특성을 가지고 있다. 특히 흡기부 압력 데이터는 펌프의 성능상태를 직접적으로 나타내는 배기 속도를 유추할 수 있는 특성을 내포하고 있다. 이러한 관측을 통해 발견한 통계학적 특성을 나타내기 위해 적응형 인자모델(APM)을 이용한 진공펌프 시스템의 실시간 진단 기법을 개발하였다. 동시에 공정 중에 배기속도를 유추 할 수 있는 배기속도지표(PSI)를 제안하여 펌프의 성능 상태를 간접적인 방법으로 관찰하는 기법을 개발하여, 두 기법을 통한 진공펌프 시스템의 상태변화 진단 결과의 경향이 동일함을 확인하였다.

• Tunnel and Underground Space
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• v.15 no.1 s.54
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• pp.71-79
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• 2005

The stability of the intersection area of two tunnels is analyzed by observational method. The depth from ground surface to the intersected area is shallow and the geology around the area consists of soil and/or weathered rock. The tunnel is supported by reinforced protective umbrella method with 12 m long 3-layer steel-pipes and the intersected area is additionally reinforced with 6 m long rockbolts. The measured displacements are converged and mechanical stability of the intersected area of two tunnels is confirmed; tunnel arch settles to 6-7 mm at the crown and the sidewalls converges to about 5 mm. So based on the displacement measurements, the supporting system for the tunnel intersection proves to be effective to not only reduce the deformation of tunnels but also maintain the stability of tunnels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1889-1894
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• 2012

A small-scale chamber test laboratory for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. Laboratory test which was simulated during construction stage was conducted. The vertical deflection of 4.43mm to 6.6mm, and the horizontal deflection of 5.49mm to 15.9 mm were measured during backfilling. In case of loading, the vertical deflection of 2.41mm to 8.69mm, and the horizontal deflection of 1.66mm to 2.53mm were measured. Its residual deflections were 1.40mm to 5.93mm for vertical and 1.66mm to 2.53mm for lateral. The vertical and horizontal deflecto of controlled low strength materials were smaller than that of sand backfill. Also, it was same trend for the measured surface settlement.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.484-492
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• 2016

This study is the numerical analysis for the ground stability assessment in ${\bigcirc}{\bigcirc}$mine. The subsidence factors applied to the numerical analysis were as follows. First, the deterioration of the rock mass properties by excavation of the disturbed zone. Second, using the average lateral pressure coefficient of Korea. Third, a study of the mine history. Fourth, the excavating collapsed rock mass in numerical analysis based on the assumption that the rock mass around the goaf was collapsed due to the mining. The developed methods were applied to the cross section (5+10) of the actual subsidence in ${\bigcirc}{\bigcirc}$mine. The feasibility of the numerical analysis methods was confirmed by providing the same results as those of the actual subsidence. Next, the developed methods were applied to the cross section (3+10) that had a high probability of subsidence and the ground stability was evaluated. The analysis results show that the vertical displacement for the 5+10 cross section occurs at a maximum of 46 mm, whereas the analysis results show that the vertical displacement for the 3+10 cross section occurs at a maximum of 7 mm. Hence, it is concluded that the probability for subsidence is low.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.871-885
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• 2017

Nowadays, the construction of tunnels with a shallow depth drastically in urban areas increases. But the effect of sidewall displacement in shallow tunnel on its behavior is not well known yet. Most studies on the shallow tunnel have been limited to the stability and the failure of the tunnel and the adjacent ground in plane strain state. Therefore, the model tests were conducted in a model ground which was built with carbon rods, in order to investigate the impact of the tunnel sidewall displacement on the lateral load transfer to the adjacent ground. The lateral displacement of the tunnel sidewall and the load transfered to the adjacent ground were measured in model tests for various overburdens (0.50D, 0.75D, 1.00D, 1.25D). As results, if the cover depth of tunnel was over a constant depth (0.75D) in a shallow tunnel, the tunnel sidewall was failed with a constant shape not depending on the tunnel cover depth and also not affected by the opposite side of the wall. But, if the cover depth of tunnel was under a constant depth (0.75D), the failure of the tunnel sidewall could affect the opposite sidewall. In addition, if the displacement of tunnel sidewall with 50% of the critical displacement occurred, the tunnel failure was found to be at least 75%. However, additional studies are deemed necessary, since they may differ depending on the ground conditions.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.259-267
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• 2002

Recently, Umbrella Arch Method(UAM) is commonly used in order to enhance the stability of tunnel itself and stabilize the adjacent surface structure. But quantitative estimation of reinforcement effect is needed because UAM is designed and constructed only on the basis of empirical experience. By using 3-dimensional finite element method, parametric study is performed for elastic modulus of ground and overburden, and reinforcement effect is analyzed quantitatively. From the results, surface settlement decreases about 9%∼27% in soil tunnel, about 4%∼24% in weathered rock tunnel and 4%∼17% in soft rock tunnel when applied with UAM. The prediction equation for final surface settlement is suggested through regression analysis and the equation is expressed as exponential function which has variable Smax, unknown coefficient i and k.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.33-44
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• 2000

In order to investigate the effect of progressive collapse of underground circular opening on surface subsidence, laboratory model tests were performed. The modelling materials were sand which has been used as KS standard. Six test models which had respectively different depths of openings were produced. Surface subsidence and horizontal displacements were measured according to progressive collapse of underground opening. Some subsidence prediction method such as NCB method, profile function method and influence function method were considered to predict the subsidence of sand models. The profile function method approximated by Gaussian error function was finally suggested as the most appropriate to sand models.