• Journal of Korean Tunnelling and Underground Space Association
• /
• v.13 no.4
• /
• pp.291-304
• /
• 2011

Recently concern for subsea tunnels is increasing, The effect of high water pressure can not be ignored in the case of a deep subsea tunnel. Reinforcement like grouting is necessary for the stability of such a subsea tunnel. In this study, therefore, it was investigated how the water barrier and shear strength increment resulted from grouting had an effect on the stability of a subsea tunnel. To this end, two-dimensional hydromechanical coupled analyses were performed for a sensitivity analysis in terms of different range, permeability coefficient, and cohesion of grouting reinforcement for the rock classes I, III, and V with respect to RMR system. The mutual relationship between strength increment and water pressure increased by barrier effect due to grouting was investigated by analyzing the numerical results.

• Proceedings of the KAIS Fall Conference
• /
• 2011.05b
• /
• pp.954-957
• /
• 2011

본 논문은 기존의 샌드 드레인 시공장비의 베이스 머신인 기중기 대신에 포크레인을 이용하여 샌드 드레인 시공 장비를 개발 하였다. 그리고 세부적인 기술 개발 사항으로 전기적 타설의 방식에서 유압 타설을 통한 작업 효율 연비 향상과 구조해석을 통한 장비의 무게의 경량화를 이루었다. 그리고 리더의 각도 조절을 통하여 작업의 향상을 도모 할 수 있는 각도 조절 장치와 타설 작업의 자동 모니터링과 제어를 할 수 있는 자동제어 시스템을 개발 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.47-47
• /
• 2010

배전계통의 사고예방 기술은 전력수요 및 증설이 증가하고 있는 상황에서 시급히 확립되어야 한다. 특히 현장에서 시공되는 케이블은 시공과정의 관리가 쉽지 않을 뿐 아니라, 시공 중 발생될 수 있는 결함들을 검출하는 방법도 제한되어 있다. 본 연구에서는 국내에 도입된 진단방법을 통계적 방법으로 분석하고 효과적으로 점검할 수 있는 방법에 관한 검토하고자 한다.

• Computational Structural Engineering
• /
• v.10 no.1
• /
• pp.70-74
• /
• 1997

LGSF Housing의 설계는 기존의 2*4 목조주택의 설계방법을 그대로 수용하되 박판의 강재를 사용한다는 특성에 따라 부재의 좌굴특성을 고려하는 점에서 큰 차이가 있다고 볼 수 있다. 따라서 부재의 허용내력은 부재의 형상에 따라 그 좌굴모드가 결정되고 각 모드 중 최소의 값이 부재의 최종 허용내력으로 결정된다. 이와 같은 성상을 살펴볼 때 LGSF Housing은 사용되는 자재의 단면형상 개발에 따라 그 내력의 증진을 기대할 수 있으며, 이에 대한 연구의 필요성이 크다고 볼 수 있다. 또한, 스틸하우스는 공장에서 제작된 스터드의 현장조립에 의하여 시공되므로 이들 부재간의 접합방법에 큰 영향을 받게 된다. 기존 외국의 시공사례를 살펴보면 부재간의 접합은 주로 핸드건 등에 의한 스크류를 사용한 접합방법이 이용된다. 따라서, 이러한 접합방법의 내력평가방법도 해결되어야 할 문제점으로 볼 수 있다. 이러한 제반 문제점 등이 해결된다면 LGSF Housing은 건설공기의 단축을 기할 수 있고, 시공의 신속.편리성을 도모할 수 있으며, 자원의 재활용이 가능하고 향후 벽체 패널의 공장생산 등을 통한 공업화 건축이 가능하다는 점 등을 고려할 때 국내 저층구조물의 설계에 새로운 방향을 제시할 수 있을 것으로 기대된다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.24 no.3
• /
• pp.231-245
• /
• 2022

When vertical shafts are constructed in soft clay with low strength, there is a risk of basal heave, which causes the excavation surface to heave due to the low bearing capacity of the ground against the imbalance of earth pressure at the excavation surface. Methods of deriving a safety factor have been proposed to evaluate the stability against the basal heave. However, there are limitations in that it is difficult to accurately evaluate the heave stability because many assumptions are included in the theoretical derivation. In this study, assuming that a circular vertical shaft is constructed in soft clay, the existing safety factor equation proposed through a theoretical approach was supplemented. Bearing capacity according to the shaft geometry, inhomogeneity of the soil, and the effect of soil plug were considered theoretically and applied in a previous safety factor equation. A three-dimensional numerical analysis was conducted to simulate the occurrence of basal heave and review the supplemented equation through various case studies. Several series of case studies were conducted targeting various factors affecting heave stability. It was verified that the additionally considered characteristics were properly reflected in the supplemented equation. Furthermore, the effects of each factor constituting the safety factor equation were examined using the results of the numerical analysis performed by simulating various cases. It was confirmed that considering the undrained shear strength increment according to depth had the most significant effect on the calculation of the safety factor.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.16 no.5
• /
• pp.19-28
• /
• 2012

In this study, cause of longitudinal crack which is found on duct slab of road tunnel is studied. In-depth investigation, such as visual inspection, non-destructive testing and geometrical surveying of duct slab, is carried out. In order to perform cause analysis, the investigated results are compared to the results of numerical analysis. Many factors, which cause longitudinal crack, are classified as constrained condition of the duct slab, location of the rebar, temperature, shrinkage and so on. According to the classified causes of longitudinal crack, numerical analysis is performed considering construction stage of the tunnel lining. Especially, in order to predict shrinkage stain due to discrepancy of curing date, ACI-209 model, KCI structural design code and other researcher's shrinkage test results are compared. The results show that shrinkage strain is one of the main factors causing longitudinal crack. Other investigated tunnels are classified along with the construction method of duct slab and patterns of cracks. As a result, improving ways to construct duct slab are suggested.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.10 no.2
• /
• pp.129-137
• /
• 2008

This paper intends to develop an assesment technique for the rapid and quantitative evaluation of tunnel safety during tunnel excavation by using displacement measurements. Control criteria for the field measurements are provided at tunnel construction sites in Korea and other countries. However, it was known that the criteria were not clear and varied depending on the construction sites. In order to make a reasonable support for guidelines, critical strain concept is introduced in this study. And the engineering meanings of the critical strain concept are investigated precisely. In order to do this, at first, the engineering meanings of the original concept from the previous researchers was investigated theoretically for the evaluation of tunnel safely. Subsequently displacement data were obtained by using the commercial program, then the evaluation of tunnel safely was conducted with the view point of previous researches. Additionally, strains are determined from the feedback analyses program by inputting measured displacements that were obtained from the commercial program, then the evaluation of tunnel safety was discussed with the critical strain concept. Consequently it can be concluded that the evaluation of tunnel safety can be determined quantitatively and rapidly in the field by introducing the critical strain concept.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.6
• /
• pp.181-187
• /
• 2003

This paper describes a study of the influence of shield tunnel construction on the displacements and stresses induced in the linings of existing nearby parallel tunnels. The paper presents a brief review of a set of laboratory scale model research programme investigating the influence of tunnel proximity and alignment, liner stiffness on the nature of the interactions between closely spaced tunnels in clay. A total of two sets of carefully controlled physical model tests were performed. A cylindrical test tank was developed and used to produce clay samples of Speswhite kaolin. In each of the tests, three model tunnels were installed in order to conduct two interaction exts that have been carried out to investigate the interaction problem between parallel tunnels. The results of these tests are compared with the results of finite element analysis to investigate the techniques that must be used to obtain reliable numerical solutions to this type of problem.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.35 no.1
• /
• pp.35-44
• /
• 2022

It is essential to control the lateral displacement and differential axial shortening of the vertical elements in high-rise buildings. Recently, an outrigger or a mega structure system has been adopted to control the lateral displacement. Furthermore, to resolve the problems caused by differential axial shortening in high-rise buildings, analytical prediction and correction is often studied; however, the study on the comparisons of the lateral load resisting systems to address differential axial shortening is less. Therefore, in this paper, a 60-story RC residential building using an outrigger or a mega structure system is analyzed with a construction sequence. Moreover, differential axial shortening can result in an additional member force of structural members and failure of non-structural members. These problems caused by differential axial shortening affects the behaviors and can damage the important structure member in the high-rise buildings. Hence, the effects of the systems on differential axial shortening between the vertical elements in high-rise buildings are studied.

• Tunnel and Underground Space
• /
• v.10 no.1
• /
• pp.25-32
• /
• 2000

This paper presents two new extensions to the DDA method. The extensions consist of sequential loading or unloading and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the DDA method with the new extensions are presented. Simulations of the underground excavation of the Unju Tunnel of Kyungbu High Speed Railway Project in Korea were carried out to evaluate the influence of excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the DDA program with the three new extensions can now be used as d practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.