• 기술발표회
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• s.2006
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• pp.331-341
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• 2006

터널 설계시 일반적으로 지반조사와 물리탐사를 시행하여 지층에 따른 적절한 터널 지보패턴을 설정하고 있으나, 다양한 지반 및 지질특성과 설계단계에서 미쳐 발견되지 못한 단층등의 연약대로 인하여 시공시 터널내에서 종종 붕락사고가 발생하고 있다. 터널 굴착시 발생하는 붕락은 터널의 안정성 저하 및 공기 지연 등의 큰 문제점들을 발생시키므로 조기에 적절한 보강방안이 요구된다. 본 논문에서는 터널 굴착시 발생한 두개의 붕락사고에 대해서 붕락원인과 붕괴유형을 파악하고 현장 여건에 맞는 신속한 보강대책을 제시하고 시공한 보강사례이다. 향 후 본 사례와 유사한 터널붕락사고가 발생할 경우 보강설계 및 보강방안을 계획.수립하는데 유용한 참고자료가 될 것이다.

• 기술발표회
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• s.2006
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• pp.199-209
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• 2006

현재 연약지반의 개량 및 구조물기초 지반의 보강을 위하여 약액주입공법 및 고압분사주입공법 등의 주입공법이 널리 행해지고 있는 실정이다. 이에 본 연구에서는 00교 교대 전면 옹벽기초 하부지반을 고압분사주입공법을 이용해 보강한 사례로서 설계 및 시공, 시험 자료를 분석하고, 보강작업에 따른 지반의 개량효과를 분석하였다. 개량효과학인을 위한 시추조사와 시추공영상 촬영 이미지 관찰결과에서는 고압분사에 의해 양호한 상태의 고결체(토사 + 시멘트 페이스트)가 형성되었음을 확인 할 수 있었으며, 고결체와 원지반의 복합지반상에서 실시한 평판재하시험 결과 및 시추조사시 채취된 고결체 Core에 대해 실시한 일축압축강도시험 결과에서도 설계시 가정한 값을 모두 만족하는 것으로 나타나 연약지반의 강도가 개량되어 안정성을 확보한 것으로 확인되었다.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.55-62
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• 2000

심층혼합처리공법에 의해 개량된 연약지반상에 사석제를 축조한 후 배면매립을 실시할 경우 사석호안의 변형거동을 관찰하기 위해 계측을 실시하였다. 개량지반상에 사석호안을 축조하기 위한 설계기준을 마련하기 위하여 유한요소법을 이용한 지반변형해석과 Bishop의 간편법을 이용한 사면안정해석을 실시하였다. 이들 해석을 사석제부, 연약지반부 그리고 뒷채음성토부의 토질조건 및 형상이 다른 여러 경우에 대하여 실시하여 그 결과를 서로 비교 분석하였다. 즉, 해석결과를 이용하여 사석제 정사부에서의 수평변위량과 침하？을 호안의 사면안정률과 연과지어 검토하였다. 본 연두결과 사석호안의 사면안전률 1.3보다 낮을 경우 상당히 큰 지반변형이 발생하는 것으로 나타났다.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.759-767
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• 2009

Recently, there is a trend to introduce a reliability approach to the design of al large scale improvement of weak ground due to the uncertainty of the influence factors in the consolidation. Since the reliability analysis is not easily adopted to geotechnical engineers because of some difficulties in working up the theories, Duncan(2000) proposed a simplified method for using reliability method to goetechnical problems. In this study, the applicability of Duncan's simplified reliability approach is evaluated by comparing the traditional reliability results with Duncan's. In the sensitivity analysis, the two results were quite similar. However, the probability of failure showed an error range of 20~50% and further Duncan's approach could not make a distinction for the distribution of geotechnical random variables. The simplified reliability method seems to be used properly in preliminary design if it is used supplementary with the deterministic method.

• Journal of Korean Society of Transportation
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• v.16 no.2
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• pp.99-105
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• 1998

이 논문은 포장체 하부구조내 공동(空洞)현상에 대한 위치를 규명하는데 있어서 신속하면서, 간단하고 신뢰성있는 방법을 제시하고자 한다. 동적관입시험(DCP)을 사용하여 콘크리트 슬라브하부의 노상토에 대한 강도를 측정하였다. 타격회수에 대한 침하의 양으로 측정되는 동적관입침하율을 비교하여 포장체하부의 연약지반에 대한 위치를 규명하였다. 콘크리트 포장체 하부의 공동(空洞)현상 및 연약화된 노상토에 대한 정보를 얻고자 하는 엔지니어를 위하여 시험방법 및 결과분석 등을 현장시험을 통하여 체계적으로 설명하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.855-867
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• 2018

When a weak zone exists ahead of tunnel face, the stress in the adjacent area would increase due to the longitudinal arching effect and the stability of the tunnel is affected. Therefore, it is critical to prepare a countermeasure through the investigation of the frontal weakness zone of the excavated face. Although there are several researches to predict the existence of weak zone ahead of tunnel face, such as geophysical exploration, numerical analysis and tunnel support, lack of studies on the relaxation zone depending on the width or distance from the vulnerable area. In this study, the impact of the weak zone on the formation of the relaxation zone was investigated. For this purpose, a series of laboratory test were carried out varying the width of the weak zone and the separation distance between tunnel face and weak zone. In the model test, sand with a water content of 3.8% was used to form a model ground. The model weak zone was constructed with dry sand curtains. The tunnel face was adjusted to allow a sequential excavation of upper and lower half part. load cells were installed on the bottom of the foundation and the tunnel face and measuring instruments for displacement were installed on the surface of the model ground to measure the vertical stress and surface displacements due to tunnel excavation respectively. The test results show that the width of weak zone did not affect the ground settlement while the ground subsidence drastically increased within 0.25D. The vertical stress and horizontal stress increased from 0.5D or less. In addition, the longitudinal arching effect is likely within the 1.0D zone ahead of the tunnel face, which may reduce the vertical stress in the ground following tunneling direction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.301-312
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• 2003

This paper considers the stresses and pore pressures induced in soft ground due to tunnelling and it presents and discusses the approach methods for estimating the stability of the tunnel and its heading during drained and undrained condition. In practical, the undrained analyses of the face stability of shield tunnelling in soft soil, are carried out based on the field data measured during tunnelling and the results are also evaluated.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.45-51
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• 2010

This study is to evaluate an application of technology to the soft ground stability using quick lime pile in the field. We investigated properties of Korean quick lime by conducting loading test and theoretical consideration about a principle and property of soft ground improvement by quicklime. According to the test results, it was estimated that quick lime pile method has dehydration effect by absorption of quick lime, consolidation effect by swelling of pile, increasing bearing by strength of pile itself and decreasing sinking effect, etc. A material property of quick lime is favorable for construction and considerable strength. In the case of higher strength is required, using cement as additive would increase material strength.

• Journal of the Korean Geotechnical Society
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• v.28 no.6
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• pp.39-52
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• 2012

Magnetic sensing system and automated monitoring system based on digital hall sensor for ground settlement are developed to change traditional method for monitoring surface settlement and underground settlement by manual type and to overcome technical limits of existing automated settlement monitoring system. It's possible to monitor surface settlement and underground settlement with multi-points at the same time in a single hole with NX size. It was possible to verify technical confidence and stability by several case studies of soft ground improvement project.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.217-227
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• 1997

The purpose of this study is to analyze the correlation of soil properties in coastal soft ground. For the purpose of this study, several coastal soft ground areas were selected. Many large scale construction works are being executed and will increase continuously in these soft ground areas. So, soil property in these areas is very important. The grounds forming coastal areas are affected by seawater movement. So, most of these areas consist of alluvium stratum. Therefore, soil properties of eastern and southern coastal areas are very complex. Many laboratory tests were executed with disturbed and undisturbed soil samples. Undisturbed samples were taken by using thin walled tubes and transported into the laboratory with caution, so as not to disturb the sample. The consistent rate of fine-grained content in these areas is over 90%. Also, these areas contain higher water content and clay content. Therefore, knowing these soil properties, it is possible to safely design fabrics and constructions.