• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.303-310
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• 2000

A new stress path testing scheme with back pressure equalization process is proposed, to compute the settlement of clay soils based on their probable deformation mode. The proposed testing scheme minimizes the efforts for testing, otherwise numerous testing works are required to simulate the probable stress paths in the field. Furthermore, the proposed testing scheme can supply anisotropic stress paths for consolidation which cannot be possible in a conventional way. The validity and effectiveness of the proposed testing scheme was investigated and confirmed with test results on remolded kaolinite clay soils. Conclusively, it is suggested that the proposed testing scheme is a very effective tool to compute settlement of clay soils and it is also very useful to investigate the anisotropic characteristics of deformation of clay soils.

• Geomechanics and Engineering
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• 제12권4호
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• pp.689-705
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• 2017

The present study deals with the Pressure-settlement behavior of square and rectangular skirted footing resting on sand and subjected to a vertical load through a laboratory experimental study. A series of load tests were conducted in the model test tank to evaluate the improvement in pressure-settlement behavior and bearing capacity of square and rectangular model footings with and without structural skirt. The footing of width 5 cm and 6 cm and length/width ratio of 1 and 2 was used. The relative density of sand was maintained at 30%, 50%, 70%, and 87% respectively. The depth of skirt was varied from 0.25 B to 1.0 B. All the tests were carried out using a strain controlled loading frame of 50 kN capacity. The strain rate for all test was kept 0.24 mm/min. The results of present study reveal that, the use of structural skirt improves the bearing capacity of footing significantly. The improvement in bearing capacity was observed almost linearly proportional to the depth of skirt. The improvement in bearing capacity of skirted footings over footing without skirt was observed in the range of 33.3% to 68.5%, 68.9% to 127% and 146.7% to 262% for a skirt depth of 0.25 B, 0.50 B and 1.0 B respectively. The skirted footings were found more effective for sand at relative density of 30% and 50% than at relative density of 70% and 87%. The bearing capacity was found to increase linearly with footing width for footings with and without skirts. This observation was found to be consistent for footings with different skirt depths and for relative density of sand i.e., 30%, 50%, 70%, and 87%. The obtained results from the study for footing with and without skirts were comparable with available solutions from literature.

• 한국농공학회논문집
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• 제54권1호
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• pp.39-45
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• 2012

In this study, field test on utilization of recycled aggregates and crushed stone as horizontal drains to use an alternative material of sand in soft ground is practiced. The settlement with time showed similarly ranged from 28.4-30.3 cm in the all horizontal materials. The excess pore water pressure of the recycled aggregates and crushed stone showed smaller than sand. The small the excess pore water pressure becomes faster the consolidation period and it can reduces the amount of residual settlement. Therefore, it was verified as having enough to an alternative materials that the field applicability is excellent. The distribution of earth pressure with time showed similarly in the all horizontal materials. The recycled aggregates and crushed stone was very applicable to practice because there is no mat resistance in the horizontal drains layer. The penetration rate in the SCP and PVD improvement sections did not show large differences as the grain size and the horizontal drainage height increases.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.399-409
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• 2018

토압분리형 교량의 보강토옹벽은 교량을 구성하는 중요 구조물이고, 횡방향 토압과 접속슬래브를 지지한다. 보강토옹벽의 침하는 상부 구조의 손상과 접속부의 단차를 유발할 수 있다. 따라서, 토압분리형 교량의 보강토옹에 대한 침하량을 면밀히 검토하는 것이 필요하다. 본 연구에서는 토압분리형 교량의 보강토옹벽에 대한 높이와 기초지반의 강성에 따른 침하량을 검토하였다. 보강토옹벽을 높이 4.0 ~ 10.0m로 설계하고, 탄성침하량을 산정하였다. 보강토 옹벽의 높이에 따라 보강토옹벽의 저면 면적과 접지압이 선형적으로 증가되었다. 그 이유는 옹벽 높이가 증가됨에 따른 보강토체의 자중의 증가 때문이다. 자중의 증가로 인해 탄성침하량도 선형적으로 증가되었다. 구조물기초설계기준 해설에 제시된 보강토옹벽 탄성침하량 이론식을 통해 침하량을 산정한 결과, 보강토옹벽의 높이가 증가됨에 따라 비례하여 침하량이 증가하였고 기초지반의 N치가 35 이상이 되어야 접속슬래브의 허용침하량을 만족하는 것으로 나타났다. 유한요소해석을 통해 보강토옹벽의 높이와 기초지반의 강성에 따른 침하량 산정 결과, 기초 지반의 강성이 증가함에 따라 최대침하량은 탄성침하량과 동일하게 감소하였다. 탄성침하량은 유한요소해석을 통해 산정된 침하량보다 과다 산정되었다. 이는 탄성침하량이 보강토체를 연성기초로 가정하고 기초 지반을 반무한 탄성체로 가정하기 때문이다. 토압분리형 교량의 보강토옹벽은 교량을 구성하는 중요 부재이므로 침하량에 대한 면밀한 검토가 필요하다. 그로인해 유한요소해석을 수행하여 침하량을 산정하는 것이 보다 합리적인 것으로 판단된다.

• Geomechanics and Engineering
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• 제24권3호
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• pp.295-305
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• 2021

In this study, design charts for estimating consolidation settlement are proposed according to finite strain consolidation theory using a nonlinear constitutive relationship equation. Results of parametric sensitivity analysis shows that the final settlement, initial height, and initial void ratio exerted the greatest effect, and the coefficients of the void ratio-effective-stress. Proposed design charts were analyzed for three regions using a representative constitutive relationship equation that enables major dredged-reclaimed construction sites in Korea. The regional design charts can be calculated accurately for the final settlement because it is applied directly to the numerical analysis results, except for reading errors. A general design chart applicable to all marine clays is proposed through correlation analysis of the main parameters. A final self-weight consolidation settlement with various initial void ratios and initial height conditions should be estimated easily using the general design chart and constitutive relationship. The estimated final settlement using the general design chart is similar to the results of numerical analysis obtained using finite strain consolidation theory. Under an overburden pressure condition, design charts for estimating consolidation settlement are proposed for three regions in Korea.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.611-618
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• 2002

In this study the CGS as an injection method by low slump mortar was performed the pilot test to confirm the applicability of this method and the effectiveness of settlement restraint. From the results, there has been concluded the construction control standard such as an institutional diameter, space, depth, injection materials, Infection pressure etc. Also, there has been estimated the ground improvement effectiveness which has resulted from the field investigation and consolidation test etc. From the results, in the adjacent ground the CGS, generally, has been confirmed to in-crease ground strength to improve the consolidation characteristic obtained from the field investigation and consolidation test. Especially, the CGS which performed the larger stiffness to the ground has been concluded that the settlement restraint to the ground complicates the ground effect which Increases the bearing capacity and stress assignment. So, the CGS can be considered as an effective method to increase the bearing capacity as well as the settlement restraint of soft ground.

• 한국지반공학회논문집
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• 제23권3호
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• pp.25-40
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• 2007

얕은 터널의 개착식 터널 라이닝에 발생하는 과잉토압은 라이닝의 변형과 손상을 유발하는 역학적 주요인자들 중의 하나이며(Kim, 2000), 과잉토압은 되메움토의 다짐불량, 자중에 의한 압밀, 강우의 침투에 의한 다짐, 차량에 의한 진동 등에 의해 발생할 수 있다(Komiya et al., 2000; Taylor et al., 1984; Yoo, 1997). 터널 라이닝에 발생하는 토압을 구하기 위한 많은 시험이 행해졌지만, 부등침하와 과잉토압을 줄일 수 있는 보강대책을 수립하기 위한 사례는 없다. 본 연구는 모래 지반에 $1.0D\sim1.5D$ 깊이에 개착식으로 시공하는 원형의 강성 터널에 작용하는 토압에 관한 것으로 진동다짐의 영향을 모형실험에서 충분히 반영하기 위하여 100Hz의 진동주파수를 사용하였다. 본 연구에서는 개착식 터널 라이링에 작용하는 부등침하와 과잉토압을 줄이기 위해서 지오텍스타일 매트를 설치하였다. 지오텍스타일 매트의 보강에 의한 부등침하와 토압의 감소효과를 확인하기 위해 실내모형실험을 수행하였다. 실내모형실험에서 토피, 매트 보강형태, 절취면의 거칠기 등을 달리하여 가장효과적인 방법을 구하였다. 절취면의 거칠기 달리하기 위해 사면에 사포#100, 사포#400과 acetate 부착하였습니다. 무보강과 매트 보강에 대한 모형실험을 실시하여 구한 토압을 비교하여 매트 보강효과를 살펴보았으며, 사진분석법(Park, 2003)을 이용하여 지반의 변형을 분석하였다.

• 한국지반공학회논문집
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• 제19권6호
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• pp.107-114
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• 2003

국내에서는 조립토를 이용한 연약지반 처리공법 중 모래다짐말뚝공법이 많이 활용되고 있으나, 모래자원의 고갈과 단가상승으로 인해 적용이 제한되고 있어 대체공법이 필요한 실정이다. 본 연구에서는 육상부 현장에 시험시공된 쇄석다짐말뚝에 대한 정재하시험을 수행하였으며, 쇄석다짐말뚝과 연약지반의 응력분담비를 규명하고 성능을 평가하였다. 임의 압력에서 치환율이 증가할수록 침하량이 작아지는 경향을 보였다. 치환율 20%일 때의 항복압력은 치환율 30%, 40%일 때 보다 작았다. 치환율 30%와 40%일 때의 항복응력과 침하량은 비슷하였다. 응력분담비는 1.7∼-3.0의 범위에 있었으며, 치환율이 증가할수록 응력분담비가 증가하는 경향을 보이고 있었다.

• 산업기술연구
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• 제21권A호
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• pp.293-301
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• 2001

This paper is experimental results of investigating the efficiency of horizontal vacuum drainage system. Effects of size and shape of drain on horizontal vacuum drainage were studied. Model tests in the laboratory with soft marine clay were carried out with drain pipe of having three different diameters and PBD (Plastic Board Drain) of strip shape so that consolidation settlement of soft clay due to applied vacuum pressure, amount of discharge, ground settlement and distributions of pore pressure and undrained shear strength were measured during testing. From results of model test, amount of discharge due to vacuum pressure was increased with the diameter of pipe drain whereas the drain efficiency of pipe in per unit area of drain surface was decreased with diameter of pipe. The rate of discharge per unit time was reduced very fast with diameter of pipe. Settlement of ground surface with time was increased with diameter of pipe as a result of increase of discharge to drain pipe.

• 한국농공학회논문집
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• 제58권2호
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• pp.31-44
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• 2016

This study analyzed pore water pressure, earth pressure and settlement through field monitoring on the project site in which raising embankments are being built through backside extension, and compared the behaviors of seepage analysis, slope stability analysis and stress-strain during flood water levels and rapid drawdown under steady state and transient condition. The variation of pore water pressure showed an increase during the later period in both upstream and downstream slope, with downstream slope more largely increased than upstream slope overall. The variation of earth pressure increased according to the increase of embankment heights, while the change largely showed in the upstream slope, it was slowly increased in the downstream slope. The settlements largely increased until 23 m as embankment heights increased, and showed very little settlement overall. Under a steady state and transient conditions, the seepage quantity per day and leakage quantity per 100 m of embankment against total storage were shown to be stable for piping. The hydraulic gradient at the core before and after raising embankments was greater than the limit hydraulic gradient, showing instability for piping. The safety factor of upstream and downstream slopes were shown to be very large at a steady state, while the upstream slopes greatly decreased at a transit conditions, downstream slopes did not show any significant changes. The horizontal settlements, the maximum shear strain and stress are especially distributed at the connecting portion of the existing reservoir and the new extension of backside. Accordingly, the backside extension method should be designed and reinforced differently from the cases of other types reservoirs.