• 지질공학
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• 제15권2호
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• pp.123-132
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• 2005

본 연구에서는 폐기물 매립장의 차수층으로 사용되는 벤토나이트 혼합토에 대한 연직침윤시험과 Frequency Domain Reflectometry 측정 장비를 이용한 유전율 측정시험을 수행하였다. 표준사, 화강풍화토, 벤토나이트 재료에 대해 다양한 배합 비율을 적용하여 제작된 벤토나이 트 혼합토의 체적함수비, 간극비, 유전율상수 등의 관계로부터 이들의 불포화 투수 특성을 파악하였다. 연구결과에 따르면 초기 벤토나이트 혼합비는 체적함수비 변화에 영향을 미치며, 체적함수비 변화는 간극비와 밀접한 관계를 가지고 있다. 또한 벤토나이트 혼합토의 체 적 함수비 변화는 유전율 반응으로부터 명확히 측정됨을 파악하였다. 벤토나이트 혼합토의 불포화 투수 특성을 파악하기 위한 본 연구에서 체적함수비와 유전율상수의 관계함수를 추정하였다.

• 한국터널지하공간학회 논문집
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• 제19권3호
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• pp.489-501
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• 2017

도심지 개착식 굴착공사 중 발생하는 붕괴사고는 공사장 내에서의 인명 및 물질적 피해를 불러일으킬 뿐만 아니라, 공사장 주변의 지반침하로 인한 도로함몰 및 시설물 피해를 유발한다. 따라서, 도심지에서 개착식 굴착공사를 수행함에 있어서, 계획, 설계 및 시공의 건설 전체 단계에서 굴착공사 붕괴 방지를 위한 철저한 대비가 필요하다. 본 연구에서는 이와 같은 개착식 굴착공사 중 붕괴사고 예방을 위해, 중점적으로 관리되어야 할 우선 요소 결정 연구를 수행하였다. 먼저, 과거 흙막이 굴착공사의 사고사례 조사결과를 분석하고, 전문가 합의에 의한 의사결정 방법인 델파이 기법을 이용하여 붕괴 유발 요소에 대한 중요도를 산정하였다. 그 결과, 지하수 처리, 지반조사의 부실, 시공상의 불안정 등이 흙막이 공사 붕괴 예방을 위한 중점 관리 요소로 도출되었다.

• Geomechanics and Engineering
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• 제22권6호
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• pp.475-488
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• 2020

The recent increase in the use of Expanded Polystyrene (EPS) geofoam in construction and geotechnical projects has driven researchers to investigate its behavior, more deeply. In this paper, a series of experimental tests to investigate the stress-strain behavior and the mechanical properties of EPS blocks, under monotonic axial loading are presented. Four different densities of cylindrically shaped EPS with different dimensions are used to investigate the effects of loading rate, height and diameter, as well as the influence of the density of EPS on the stress-strain response. The results show that increasing the height of the EPS samples leads to instability of the sample and consequent lower resistance to the applied pressure. Large EPS samples show higher Young's modulus and compressive resistance due to some boundary effects. An increase in the rate of loading can increase the elastic moduli and compressive resistance of the EPS geofoam samples, which also varies depending on the density of the samples. It was also determined that the elastic modulus of EPS increases with increasing EPS density. By implementing an efficient numerical procedure, the stress-strain response of EPS geofoam samples can be reproduced with great accuracy. The numerical analysis based on the proposed method can used to evaluate the effect of different factors on the behavior of EPS geofoam.

• 한국터널지하공간학회 논문집
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• 제16권2호
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• pp.225-236
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• 2014

본 연구에서는 지하 저류조 설치에 따른 주변지반의 지반공학적인 특성(간극비, 전단강도)을 전단파 속도를 이용하여 예측하는 것을 목적으로 하였다. 이를 위해 응력 단계별로 전단파 속도와 밀도 상관관계를 실험을 통해 도출하고 밀도와 전단강도 상관관계를 직접전단실험을 통해 획득하였다. 도출된 응력 단계별 전단파 속도와 밀도 상관관계 및 밀도와 전단강도 상관관계를 바탕으로 현장 전단파 속도를 이용하여 대상 지반의 깊이별 전단 강도를 산정하는 방법을 제시하였으며 제시된 기법을 이용하여 지하 저류조 구조물 적용에 따른 시공후 지반거동을 평가하였다. 제시된 방법으로 도출된 전단강도는 현장실험 결과와 유사한 값을 보이며 지반특성 분석에 적용 가능성을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.833-841
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• 2008

Recently, the upheaval generation in the road which is under service had been reported. Due to the upheaval generation, total 4 lanes were forced to curtail to 3 lanes, and traffic was delayed. In normal situation of cut-slopes in korea, that condition is hard to detect since most cut-slopes contain discontinuous material, that is rock. Common collapses in rock-slopes is wedge failure, plane failure and toppling failure which is all individual mechanism of discontinuous rock mass. In contrast, such upheaval in the road in front of cut-slope can be generated only when circular movement is triggered within the cut-slope. In this sense, rock-slopes barely show any kind of movement in the road locates at the front of them. Numerical analysis is general method in simulation of slope displacement and evaluation of safety. However, numerical analysis programs which are related with rock-slopes are not able to simulate such upheaval movement because that programs are based on discontinuous modeling mechanism. In addition, although numerical analysis programs which are based on FEM/FDM and thus utilize continuous modeling mechanism are able to simulate circular movement and upheaval situation, they have weakness in reflecting discontinuities of rock-slope itself. In this study, detailed in-site investigation and numerical analysis based on in-site condition were performed in order to expect upheaval movement in the road. In this procedure, the FLAC program which uses continuous modeling method was utilized, and new approach reflecting discontinuity developed toward the road with a ubiquitous joint model was tried to derive reliable analysis result.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.229-241
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• 2008

In order to investigate stabilization effect on As-contaminated soils treated by zero-valent iron(ZVI) and industrial by-products, batch tests and column tests were carried out with As-contaminated soils collected from farmland around the abandoned mine site. In batch tests, ZVI and industrial by-products(blast furnace slag, steel refining slag and oyster shell powder) were used as treatment materials to reduce As. Industrial by-products were mixed with As-contaminated soils, in the ratio of 1%, 3%, 5% and 7% on the weight base of dried soil. After incubation, all samples showed the reduction of As concentration and it was expected that ZVI and steel refining slag were effective treatment materials to remove As among treatment materials used in batch test. In column tests, columns were made by acrylic with the dimension of diameter=10cm, height=100cm, thickness=1cm and these columns were filled with untreated soils and treated soils mixed with ZVI and steel refining slag(mixing ratio=3%). Distilled water was discharged into the columns with the velocity of 1 pore-volume/day. During test, pH, EC, Eh and As concentration were measured in the regular term(1 pore-volume). As a result, ZVI and steel refining slag were shown 93%, 62% reduction of As concentration respectively by comparison with untreated soils. Therefore, if ZVI and steel refining slag are used as treatment materials in As-contaminated soils, it is expected that the As concentration in soils is reduced effectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1148-1155
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• 2010

To suggest a modified shallow foundation design method which can be considered the scale effect of foundation on IGM(intermediate geomaterial) soil layer, the weathered soil layer that is uniformly formed up to 8m(2B) with over 50 N-value is selected and 3 times field loading tests are performed on several sized square-shaped shallow foundations with 30, 75, 150, 240 and 400cm in width respectively. Because the soil modulus of elasticity(Es) calculated by soil investigation and 1st field test(PBT) results showed an underestimated tendency, a modified correlation is required for the reasonable estimation of Es on the weathered soil. Also, the N-value was increased with an increasing in depth. However, the N-values around the test foundations showed the different values even though the foundations on the same level because the test site was arranged by excavation. Therefore, the more detail soil investigations are required for the each test foundations respectively. Since Es based on elasticity theory is determined by the stress distribution shape of the foundation and elasticity modulus of the soil, the scale effect considered pressure-settlement curve can be clearly derived from the correlation on stress distribution shape and the variation of soil elasticity modulus with depth. Therefore, the modified correlation will be suggested to estimate a reasonable Es on the weathered soil, and the scale effect considered shallow foundation design method is also developed based on the elastic theory and field tests in this research.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.562-570
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• 2010

This study was conducted to estimate the number of disc cutter consumption and to predict amount of disc cutters when a shield TBM(Tunnel Boring Machine) of the Han Riverbed Tunnel was applied. In fact, it is almost impossible to change the machine after starting the excavation using the shield TBM method. Therefore, it is important to design an appropriate equipment in the shield method - an efficiency choice of the operation equipment plays a key role in the shield tunnel processing. For the above reason, the disc cutter consumption prediction is quite important so that the detailed analysis is required. A number of disc cutter consumption was predicted by the three methods, viz. KOMATSU, MITSUBISHI and NTNU. In addition, the predicted results were compared with field data. The prediction of disc cutter consumption showed that 237 for KOMATSU, 501 for MITSUBISHI, and 634 for NTNU, respectively. However, a total number of 1,263 disc cutter consumption were investigated during the tunnel construction. It was found that there was a huge difference between the predicted and real values of the disc cutter consumption. The more detailed investigation showed that the disc cutter was worn out bluntly in the northbound tunnel, meanwhile it was worn out sharply in the southbound tunnel. In particular, the disc cutter consumption in the southbound tunnel was increased rapidly because of rear abrasion for remaining mucks in the chamber.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1046-1053
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• 2006

In the large scale recent reclaiming works performed within the wide spatial boundary, evaluation of long-term consolidation settlement and residual settlement of the whole construction area is sometimes made with the results of the limited ground investigation and measurement. Then the reliability of evaluation has limitations due to the spatial uncertainty. Additionally, in case of large scale deep excavation works such as urban subway construction, there are a lot of hazardous elements to threaten the safety of underground pipes or adjacent structures. Therefore it is necessary to introduce a damage prediction system of adjacent structures and others. For the more accurate analysis of monitoring information in the wide spatial boundary works and large scale urban deep excavations, it is necessary to perform statistical and spatial analysis considering the geographical spatial effect of ground and monitoring information in stead of using diagrammatization method based on a time-series data expression that is traditionally used. And also it is necessary that enormous ground information and measurement data, digital maps are accumulated in a database, and they are controlled in a integrating system. On the abovementioned point of view, we developed Geomonitor 2.0, an Internet based real time monitoring program with a new concept by adding GIS and geo-statistical analysis method to the existing real time integrated measurement system that is already developed and under useful use. The new program enables the spatial analysis and database of monitoring data and ground information, and helps the construction- related persons make a quick and accurate decision for the economical and safe construction.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.219-228
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• 2006

In urban areas, tunnelling induced ground deformations, particularly ground settlements should be considered in order to minimize the damage of adjacent structures. Therefore, an appropriate monitoring system for the tunnel construction should be setup at the planning or design stage. A number of studies on ground settlements due to tunnelling in soft ground have been carried out so far. However, most studies have focused on clay soil rather than sand soil. In particular, a few studies on behaviour of subsurface deformations in granular material have been reported. In this study, two-dimensional laboratory model test with aluminium rods regarded as continuum granular material and close range photogrammetric technique, and numerical analysis were carried out in order to identify the behaviour of subsurface deformations due to shallow tunnelling. Direction and magnitude of displacement vectors from the model test was identical to the numerical analysis. In particular, the vector direction was appeared to be toward a point below the tunnel invert level. A narrow 'chimney or tulip like' pattern of vertical displacement was confirmed by both the model test and numerical analysis. This is consistent with the field data. In addition to the qualitative comparison, the quantitative comparison of subsurface settlements according to 2D volume loss showed good agreement between the model test and numerical analysis. Therefore, close range photogrammetric technique applied in the model test may be used to validate the result from the continuum numerical analysis.