• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.189-198
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• 2006

This paper concerns the finite element (FE) modeling approach for NATM tunneling in water bearing ground within the framework of stress-pore pressure coupled analysis. Fundamental interaction mechanism of ground and groundwater lowering was first examined and a number of influencing factors on the results of coupled FE analysis were identified. A parametric study was then conducted on the influencing factors such as soil-water characteristics, location of hydraulic boundary conditions, the way of modeling drainage flow, among others. The results indicate that the soil-water characteristics plays the most important role in the tunneling-induced settlement characteristics. Based on the results, modeling guidelines were suggested for stress-pore prssure coupled finite element modeling of NATM tunneling.

• 한국지진공학회논문집
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• 제2권4호
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• pp.23-30
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• 1998

지진시 지진의 3가지 진동 성분이 나타난다. 즉 수평진동 성분, 지반의 연직 진동에 의해 발생된 상부 구조물과의 피드백의 의한 말뚝의 연지 진동, 그리고 연직 지반 진동에 의한 해수의 진동, 즉, 해진이 그것들이다 이들 진동들을 해양에 설치된 개단 강관 말뚝 주변에 유발된 간극수압의 크기와 관내토 폐색력에 영향을 미칠수 있다 지반과 말뚝의 진동은 유사 지진 진동으로써 흙과 말뚝을 진동시켜서 모델링할 수 있지만 연직 지반 거동에 의해 유발된 해진 진동은 해저면에 정현파 형상의 동수압을 가해주어 모델링할 수 있다 이 연구에서는 유사화된 지진과 해진시 압력토조에 설치된 개단강관말뚝에 유발된 간극수압의 발생양상과 이에 따라 관내토 폐색력의 저감원인을 관찰하였다 연직 지진 진동시 관내토 상단에서는 관내토 하단에서와 비슷한 크기의 간극수압이 발생하였으므로 관내토에서는 상향의 침토가 유발되지 않았으며수평지진 진동시 관내토에서는 상향의 침트를 유발시켜 관내토 폐쇄력을 20%정도 저감시켰다. 해진시 수심이 220m 이상의 심해에 설치된 개단 강과 말뚝의 경우 관내토 하부 지반과 관대토 상단과의 매우 큰 동수경사로 인하여 관내토 내에 상향의 침투가 발생하여 관내토의 폐색을 파괴시켰다.

• 한국지반신소재학회논문집
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• 제13권1호
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• pp.11-22
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• 2014

본 연구는 보강과 동시에 수평배수를 겸용하는 상향식 쏘일네일에 대한 지반거동을 파악하기 위해서 모형실험과 수치해석을 이용하여 그 거동을 연구하였다. 모형실험은 모형토조 내에 상대밀도 및 강우강도 조건별로 풍화토 지반의 모형사면을 만들고 그 위에 인공강우를 뿌리는 실험을 통해 쏘일네일을 설치하지 않는 무보강조건과 배수기능을 겸한 상향식 쏘일네일을 설치하는 보강조건으로 나누어 실험을 실시하였다. 또한 실험결과를 검증하기 위하여 침투해석 프로그램인 SEEP/W를 사용하여 모형실험이 시행된 조건으로 침투해석을 실시하고 그 결과를 비교분석하였다. 본 연구 결과 강우로 인한 지하수위와 간극수압의 변화는 수치해석의 경우는 지체시간이 없이 변화되는데 비하여 모형실험은 지체시간이 있는 상태로 나타났지만 전반적으로 최종 도달시점의 측정값은 유사하게 나타나 수치해석으로 모형지반을 모사할 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 연약지반처리위원회 봄 학술발표회 논문집 연약지반처리
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• pp.13-46
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• 1994

Artificial ground freezing methods have been applied to geotechnical construction projects for stabilizing earth materials and controlling water seepage into the ground. However, this can result in frost heaving and causes the same engineering problems as encountered with the natural freezing of soil. In natural freezing, the ground freezes from the surface downward. When artificial ground freezing is applied at a deep location, however, freezing is limited locally. The soil condition differs between them as follows: Natural freezing - unsaturated and without overburden pressure. Artificial freezing -- saturated and under overburden pressure. The authors investigated the practical application of artificial ground freezing and examined the frost behaviour of a saturated soil under overburden pressure. This paper presents the results obtained from experiments concerning frost heaving and discusses frost heaving at the freezing site.

• 한국지반공학회논문집
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• 제28권5호
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• pp.85-94
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• 2012

최근 동결지반의 다양한 문제들에 대한 관심이 증대하면서 동결의 영향을 받는 지반의 거동특성에 관한 이론정립 및 체계적인 연구의 필요성이 제기되고 있다. 기존의 정립된 토질역학 이론과는 달리 동결지반에서 온도의 영향과 간극수의 동결에 의한 상변화는 간극수의 이동, 지반팽창, 작용토압의 급격한 증가 등 여러가지 문제들을 야기한다. 본 논문에서는 비동결-동결 전이 상태에서 연속성을 갖는 새로운 응력변수를 도입하여, 동결 작용을 받는 다공질 재료에 대한 THM 역학적 탄소성 구성모델을 유도하였다. 개발된 구성모델을 1차원 팽창압, 동결토의 삼축압축 강도 그리고 일방향 동결실험에 적용하여 해의 안정성과 구성모델의 적용성에 대하여 논의하였다. 수치해석 결과는 동결토의 복잡한 THM현상들을 효과적으로 묘사할 수 있었으며, 동결의 영향하에 있는 지반구조물의 해석과 설계 및 시공될 구조물의 장기거동예측에 활용될 수 있을 것이다.

• Geomechanics and Engineering
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• 제29권3호
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• pp.321-329
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• 2022

Tunnel site where high water pressure is applied, such as subsea tunnel, generally selects the shield TBM (Tunnel Boring Machine) to maintain the tunnel excavation face. The shield TBM has cutters installed, and the cutters wear out during the process of excavation, so it should be checked and replaced regularly. This is called CHI (Cutterhead Intervention). The conventional CHI under high water pressure is very disadvantageous in terms of safety and economics because humans perform work in response to high water pressure and huge water inflow in the chamber. To overcome this disadvantage, this study proposes a new method to dramatically reduce water pressure and water ingress by injecting an appropriate grout solution into the front of the tunnel face through the shield TBM chamber, called New Face Grouting Method (NFGM). The tunnel model tests were performed to determine the characteristics, injection volume, and curing time of grout solution to be applied to the NFGM. Model test apparatus was composed of a pressure soil tank, a model shield TBM, a grout tank, and an air compressor to measure the amount of water inflow into the chamber. The model tests were conducted by changing the injection amount of the grout solution, the curing time after the grout injection, and the water/cement ratio of grout solution. From an economic point of view, the results showed that the injection volume of 1.0 L, curing time of 6 hours, and water/cement ratio of the grout solution between 1.5 and 2.0 are the most economical. It can be concluded that this study has presented a method to economically perform the CHI under the high water pressure.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.97-104
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• 2006

The centrifuge and 1-g shaking table tests were performed simultaneously to compare the dynamic behaviors of loose sands of same geotechnical properties. The prototype soils were 10 m thick liquefiable loose sands. The geometric scaling factors were 20 for 1-g and 40 for centrifuge tests. The excess pore pressure, surface settlement, and acceleration in the soil were measured at the same locations in the 1-g and centrifuge tests. The total excess pore pressure from development to dissipation was measured. In the centrifuge test, viscous fluid was used as the pore water to eliminate the time scaling difference between dynamic time and dissipation time. In the 1-g tests, the steady state concept was applied to determine the unit weight of the model soil, and two different time scaling factors were applied for the dynamic time and the dissipationtime. It is concluded that the 1-g tests can simulate the excess pore pressure of the prototype soil if the permeability of the model soil is small enough to prevent dissipation of excess pore pressure during shaking and the dissipation time scaling factor is properly determined.

• 산업기술연구
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• 제25권B호
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• pp.63-71
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• 2005

This paper is an experimental result of investigating lateral soil movements at piled bridge abutments by using the centrifuge model facility. Three different centrifuge model experiments, changing the methods of ground improvement at bridge abutment on the soft clayey soil (no improvement, preconsolidation and plastic board drains (PBD), sand compaction pile (SCP) + PBD), were carried out to figure out which method is the most appropriate for resisting against the lateral soil movements. In the centrifuge modelling, construction process in field was reconstructed as close as possible. Displacements of abutment model, ground movement, vertical earth pressure, cone resistance after soil improvement and distribution of water content were monitored during and after centrifuge model tests. As results of centrifuge model experiments, preconsolidation method with PBD was found to be the most effective against the lateral soil movement by analyzing results about displacements of abutment model, ground movement and cone resistance. Increase of shear strength by preconsolidation method resulted in increasing the resistance against lateral soil movement effectively although SCP could mobilize the resistance against lateral soil movement. It was also found that installment with PBD beneath the backfill of bridge abutment induced effective drainage of excess pore water pressure during the consolidation by embanking at the back of the abutment and resulted in increasing the shear strength of clay soil foundation and eventually increasing the resistance of lateral soil movement against piles of bridge abutment.

• 한국조경학회지
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• 제35권3호
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• pp.105-113
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• 2007

This study was conducted to analyze the effects of environmental factors such as soil moisture, light intensity, temperature and humidity on changes in cambial electrical resistance. To improve data quality, cambial electrical resistance was continuously measured at fixed points by using a data logger isolated from alternating current. The relationship between environmental factors and changes in cambial electrical resistance was also analyzed. The results are as follows: 1. Cambial electrical resistance is highly correlated to the temperature of the measured area(r=-0.934). Therefore, temperature compensation is needed to analyze the effects of other environmental factors on cambial electrical resistance changes. 2. If temperature is compensated for, the change of cambial electrical resistance is highly correlated to water vapor pressure(r=-0.836). 3. If temperature and humidity are compensated for, the change of cambial electrical resistance is highly correlated to intensity of light(r=-0.738). 4. Diurnal deviation of soil water potential is not more significantly related than the change of cambial electrical resistance. However, in the long-term, soil water potential and cambial electrical resistance are highly correlated(r=-0.831). This indicates that soil moisture significantly influences the long-term change of cambial electrical resistance.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.448-454
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• 2007

This study was conducted to develop a 100 kPa soil tensiometer mainly consisted of a porous ceramic cup, water-holding tube, and a digital vacuum gauge, through theoretical design analysis and experimental performance evaluation. Major findings were as follows. 1. Theoretical analysis showed that air entry value of a porous media decreased as the maximum effective size of the pore increased, and the maximum diameter of the pores was $2.9\;{\mu}m$ for measuring up a 100 kPa of soil-water tension. 2. Property analysis of tensiometer porous cups supplied in Korean domestic market indicated that main components were $SiO_2$ and $Al_2O_3$ with a porosity range of $33.8{\sim}49.3%$. 3. The porous cup selected through sample fabrication and air-permeability tests showed weight ratios of 87% and 11% for $Al_2O_3$ and $SiO_2$. The analysis of SEM (scanning electron microscope) images showed that the sample was sintered at temperatures of about $1150^{\circ}C$, which consisted of pores with sizes of up to 25% of those for commercial porous cups. 4. The prototype soil tensiometer was fabricated using the developed porous cup and a digital vacuum gauge that could measure water tension with a pressure of 85 kPa in air tests. 5. In-soil tests of the prototype conducted during a period of 25-day drying showed that soil-water tension values measured with the prototype and commercial units were not significantly different, and soil-water characteristic curves could be established for different soils, confirming accuracy and stability of the prototype.