• Proceedings of the Korean Geotechical Society Conference
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• 1996.10a
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• pp.159-164
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• 1996

• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.43-50
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• 2012

In this research, the value of consolidation index was investigated. The range of the investigated standard deviation was analyzed and the deviation based settlement was calculated. Also, the compression index, which is the effect of the uncertainty in the ground was analyzed using the flimsy ground construction method. The settlement behavior in each embankment compaction stage was analyzed by applying the precompression load method, drainage expediting method, and displacement method through numerical analysis. In addition to the above, the settlement behavior was studied by analyzing the Piled Raft method which is stable for long term settlement. As a result, the final settlement amount based on average analysis results was that the settlement based on each of the average interpretation value, mean value of the maximum and minimum value and average compression index was different. The result of the comparison shows the difference in variation coefficient by the difference in time. Amongst them, the Piled Raft method shows the most consistent variation coefficient regardless of time and it also was least affected by the compression index of uncertainty.

• Journal of the Korean GEO-environmental Society
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• v.19 no.9
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• pp.21-28
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• 2018

In this study, a standard consolidation test (Oedometer) was performed on the relative density of sand in the south coast to evaluate long-term creep settlement characteristics. Experimental results show that the cumulative settlement at the final loading stage decreases as the relative density increases and the variation of the void ratio decreases. As a result of analyzing the settlement rate of long-term creep of sand, creep settlement of 4.7~11.0% occurred depending on relative density with respect to total settlement. The creep parameter, Beta, of Schmertmann et al. (1978) was estimated to be 0.17~0.40 (average 0.21), and it tended to converge to a certain value when the load step becomes more than a certain level. It was found that there is no significant difference in the creep parameter depending on the layer thickness, and it was confirmed that the creep parameter could be applied regardless of the field layer thickness.

• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.143-150
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• 2009

Material functions about effective stress, permeability, coefficient of consolidation and coefficient of volume change has important role to predict consolidation velocity and settlement of soft ground. Modified oedometer for radial drainage is adapted to find out material functions on laboratory tests. Undisturbed sample for laboratory tests were taken from construction sites of industrial complexes on southern coastal area which consists of upper dredged fill and lower original clay layer. For different drainage condition in consolidation process void ratio, effective stress, permeability, coefficient of consolidation and coefficient of volume change has been assessed with results of existing standard oedometer tests. It is worthwhile to note that consolidation material functions could be expressed as regression equation by Stark (2005), heterogeneity for permeability could be assessed from these relationships.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.377-386
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• 2010

This study was conducted to find out the characteristics of the expanded road embankment constructed by the lightweight air-mixed soil (slurry density $10kN/m^3$) for a short-term without any ground improvement. Compression strength, capillary rise height of the lightweight air-mixed soil and settlement behavior of soft ground were studied. Compression strengths of the specimens sampled at the site after 1 and 5 months of construction were all satisfied the required strength 500 kPa. However, it was not convinced the homogeneity construction, because the values of strength were depending on the sampled location. Also, strength difference between laboratory and site specimens were found about 19%, and thus it should be considered for mixing design. Capillary rise reached about 20 cm for 70 hours because of a numerous tiny pores existed inside the lightweight air-mixed soil. Relationship between settlement and time of the soft ground placed underneath the expanded embankment was estimated by using the measured data and back analysis technique. The current average consolidation ratio and the final settlement after 120 months later were estimated about 32% and 4.5cm, respectively. This settlement is much less value than the allowable settlement 10cm for this structure.

• Journal of the Korean GEO-environmental Society
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• v.18 no.5
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• pp.5-16
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• 2017

In the present work, a number of advanced three-dimensional (3D) parametric finite element numerical analyses have been conducted to study the behaviour of a single pile in consolidating ground from coupled consolidation analyses. A single pile with typical minimum and maximum ranges of fill height and clay stiffness has been modelled. The computed results demonstrate that the higher the height of the fill above the clay surface and the smaller the stiffness of the clay, the higher the dragloads and the negative skin friction-induced pile settlements. It has been found that the development of dragloads and pile settlement is more governed by the stiffness of the clay rather than the height of the fill. Positive shaft resistance is mobilised only after the average degree of consolidation is larger than 50%. Although the pile is installed when the degree of consolidation is 50% or more, relatively large negative skin friction can nevertheless develop on the pile. On the other hand, when a load is applied on the pile experiencing an increase in the negative skin friction with time during consolidation, the pile undergoes a large increase in the final settlement of up to 95% compared to that of a pile without axial load on the pile head. The allowable pile capacity when there is negative skin friction on the pile is reduced by about 4-11% compared to a pile without negative skin friction.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.83-96
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• 2001

선행압밀공법에서 지반으로부터 배출되는 물을 신속히 배수시키기 위해 연약지반상에 수평배수층을 설치한다. 종전의 연구에 의하면(예, Giroud(1981), 한국도로공사(1998)), 배수층의 통수능은 성토하중의 성토기간 또는 압밀속도의 영향을 받으며, 성토기간이 짧을 때에는 과다한 배수능이 요구된다. 이 논문에서는 선행압밀공법에 적용 가능한 새로운 압밀해석방법을 사용하여 소요통수능을 재검토하고 새로운 실용공식을 제안하였다. 전반적인 압밀침하량이 5%이내에서 지연될 때에는 소요통수능은 성토기간의 영향을 받지 않는다는 것을 알게 되었다. 또한 소요통수량은 압축지수, 압밀계수 및 수평배수층의 배수거리의 제곱에 비례한다는 것도 밝혀졌다.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.105-115
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• 2000

본 연구는 현실에 부합하는 연약지반의 압밀거동을 예측하기 위한 연구로서, 일단 3차원 배수 조건하에서 지반의 자중 및 압축성과 투수성의 비선형적 성질이 고려된 비선형 압밀모델을 구성하였다. 또한 연직 배수재의 시공과정에서 발생할수 있는 지반의 교란현상 및 다양한 이질층의 구성, 점증적인 하중재하 조건, 연직배수재의 부분관입 조건에 대한 고려가 가능하도록 비선형 압밀모델을 수정, 보완하였다. 이상의 연구결과를 바탕으로 유한차분방법에 의한 수치해석을 실시하였고 최종적으로 각종 희귀분석과정을 도입한 3차원 비선형 압밀해석 프로그램을 개발하였다. Ska-Edeby의 시험시공 사례를 통한 개발 프로그램의 검증을 실시하였는데, 시험시공 사례의 경우, 현장에서 측정한 깊이별 침하량 및 간극수압 결과를 개발 프로그램에 의한 예측결과와 비교, 분석하였다. 또한 개발 프로그램을 이용하여 다층지반 해석과 관련된 기존 해석방법의 문제점 및 지반의 교란효과와 연직배수재의 부분관입조건, 점증적인 하중재하 조건등이 지반의 압밀거동에 미치는 영향에 대해 살펴보았다.

• Korean Journal of Agricultural Science
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• v.27 no.1
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• pp.39-47
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• 2000

A large scale field test of prefabricated vertical drains is performed to analyze the effect of parameters of the very soft clay at a test site. Compression index and the coefficient of horizontal consolidation obtained by back-analysis from the settlement data were compared with those obtained by means of laboratory tests. The Hyperbolic, Asaoka's and The Curve fitting methods are used to estimate final settlements and coefficients of consolidation. 1. Final settlement predicted with the Hyperbolic method was the largest, and the settlements predicted with the Asaoka's and the Curve fitting methods were nearly the same range, and it was concluded that smear effect has to be considered on design in the case that spacing of drains is small 2. The relationships of the measured consolidation ratio (Urn) and the designed consolidation ratio($U_t$) were showed as $U_m$ = (1.13~1.17)$U_t$, $U_m$ = (1.07~1.20)$U_t$, $U_m$ = (1.13~1.17)$U_t$ on the Hyperbolic, Asaoka's and the Curve fitting methods, respectively. The relations on the Asaoka's and the Curve fitting methods were nearly the same range. 3. The relationships of the field compression index($C_{cfield}$) and virgin compression index($V_{cclab}$) were showed as $C_{cfield}$ = (1.26~1.45)$V_{cclab}$, $C_{cfield}$ = (1.08~1.15) $V_{cclab}$, $C_{cfield}$ = (1.04~1.21)$V_{cclab}$, on the Hyperbolic, Asaoka's and the Curve fitting methods, respectively. 4. The ratio ($C_h/C_v$) of the coefficient of vertical consolidation and the coefficient of horizontal consolidation that is obtained by back-analysis from the settlement data was $C_h$=(0.7~0.9)$C_v$, $C_h$=(0.9~1.5)$C_v$, $C_h$=(2.4~3.0)$C_v$ on the Hyperbolic, Asaoka's and the Curve fitting methods, respectively. 5. It was concluded that the exact consolidation coefficient must be determined after the final settlement is predicted again when the consolidation is finished, because the field consolidation coefficient is decreased as the time allowed to be alone is increased.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2004.11a
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• pp.52-52
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• 2004