• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.599-606
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• 2000

본 연구는 피에조콘(Piezocone) 관입 시험에 의한 과잉간극수압의 소산(Dissipation)특성을 파악하기 위하여, 실측된 소산실험 결과치와 Gupta & Davidson에 의해 개발된 연속 공동확장이론(Successive Cavity Expansion Theory) 모델을 비교하였고, 그 경험적 이론의 적합성을 규명하였다. 연속 공동확장 이론이란, 콘 관입이 유발하는 관입 주변지반의 변환 메커니즘을 연속적인 공동확장의 전개과정로 파악할 때, 관입주변의 연속적 공동확장 영역에서 발생된 과잉간극수압들은 연속적으로 소산되어지고, 결국에는 관입멈춤직후 얻게 되는 소산시험의 결과도 이러한 과잉간극수압의 연속적 소산 메커니즘으로부터 그 영향을 받는다는 개념이다. 본 연구의 실험방법은 Piezocone 관입을 위한 연약모형지반 조성을 위하여 초대형 Slurry Consolidometer에 Slurry를 45일간 압밀시킨후 Calibration Chamber(Louisiana State University Calibration Chamber System)에 옮긴 후 2차 압밀시키는 Two-Stage Consolidation Method를 사용하였다. 또한 모형지반내에 8개의 Piezometers를 설치하여 Piezometers를 설치하여 Piezocone 관입시 유발되는 지반 내에서의 과잉간극수압의 변환을 측정하였다. 실험결과와 이론 예측치를 비교함으로써 연속 공동확장이론 모델은 u$_2$형식의 피에조콘 관입 소산시험 결과들과 잘 들어맞는 모습을 보여줬으나, 관입으로 인한 주변 지반의 과잉간극수압의 소산변화는 정성적으로만 모사 되는 모습을 보여줬다.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.3 no.1
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• pp.52-61
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• 2000

Permeability is important factor in the geotechnical problems, such as seepage discharge and dissipation of excess pore water pressure. The Kozeny-Carman equation works well for graded soils but serious discrepancies are found in clays. Major factor for these discrepancies is the tortuous flow path and unequal pore size. To estimate the permeability of fine grained soils, a permeability equation in which swelling potential is coupled with Kozeny-Carman equation is proposed in this study. To verify proposed equation, a series of variable head permeability test was carried out for steel making slag and sludge mixed with bentonite. The coefficients of permeability which is measured in the laboratory is compared with the values by the proposed equation. From the comparison, it is shown that the proposed equation can predict the coefficient of permeability of clays with satisfaction. As steel making slag and sludge is industry waste, it is reused as material of road foundation and cement but the rate of use is low. It mixed sodium-bentonite with high swelling property and permeability decrease effect. Then, Admixture investigates reuse possibility as liner of waste fill.

• Journal of the Korean Geosynthetics Society
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• v.15 no.1
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• pp.47-57
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• 2016

Many researchers reported that artesian pressure exists in thick soft ground of Busan Nakdong river estuary. Artesian pressure in soft ground could affect rate of consolidation, settlement and drainage capasity of prefabricated vertical drain(PVD). This paper investigated consolidation behaviors of soft ground with partially penetrated PVD subjected to artesian pressure. Laboratory tests with 1-dimensional large column equipment and their numerical analyses were carried out. Test results showed that the consolidation settlement of clay ground with artesian pressure was higher than that without artesian pressure. Due to artesian pressure, the dissipation rate of excess pore water pressure was reduced in soft ground with artesian pressure, especially at bottom part of clay ground. Numerical results were in good agreement with experimental test results.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.47-54
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• 2011

Consolidation behavior of soft clay is generally to be affected by its compressibility and deformation characteristics. Especially, soil permeability depends on soil characteristics including its type of anisotropy. Coefficient of permeability of soft clay is mostly estimated by using laboratory(Oedometer test) and in-stiu piezocone test. The permeability characteristics of soft clay is estimated by excess pore pressure dissipation test results. In this study, the tests were performed to find out the validity of the existing theoretical formula in clay by pore pressure dissipation test and laboratory test results. After grasping of variation the coefficient of permeability ratio(${k_{h}/k_{v}}$) in different clay soils, it was found out adequate solution of in-stiu permeability ratio(${k_{h}/k_{v}}$). Piezocone tests and laboratory tests were performed at the site of pilot project of ground improvement at Yangsan-Mulgeum, Gyeongsangnam-do. Comparisons of the estimated values of ${k_{h}/k_{v}}$ using piezocone tests results and those from laboratory consolidation tests were carried out. Test results show that values of ${k_{h}/k_{v}}$ by piezocone test result(5.85) is similar of it's laboratory test(5.28).

• Geomechanics and Engineering
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• v.33 no.3
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• pp.231-242
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• 2023

This paper represents a comparative study in which Gene Expression Programming (GEP), Group Method of Data Handling (GMDH), and multiple linear regressions (MLR) were utilized to derive new equations for the prediction of time-dependent bearing capacity of pile foundations driven in cohesive soil, technically called pile set-up. This term means that many piles which are installed in cohesive soil experience a noticeable increase in bearing capacity after a specific time. Results of researches indicate that side resistance encounters more increase than toe resistance. The main reason leading to pile setup in saturated soil has been found to be the dissipation of excess pore water pressure generated in the process of pile installation, while in unsaturated conditions aging is the major justification. In this study, a comprehensive dataset containing information about 169 test piles was obtained from literature reviews used to develop the models. to prepare the data for further developments using intelligent algorithms, Data mining techniques were performed as a fundamental stage of the study. To verify the models, the data were randomly divided into training and testing datasets. The most striking difference between this study and the previous researches is that the dataset used in this study includes different piles driven in soil with varied geotechnical characterization; therefore, the proposed equations are more generalizable. According to the evaluation criteria, GEP was found to be the most effective method to predict set-up among the other approaches developed earlier for the pertinent research.

• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.41-46
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• 2009

In this paper, a series of model tests were performed in laboratory to evaluate promoting consolidation of compaction pile methods for soft ground improvement. For the model tests, composite soil samples that have 10% replacement area ratio were prepared by using sand, gravel, and sandy gravel for the materials of compaction piles. After loading to each composite soil sample, the excess pore pressure dissipation and settlement were investigated. In addition, the behavior of clay mixed with each compaction pile was also monitored at the end of consolidation to evaluate clogging phenomenon. As a test result, the effects for decreasing settlement and promoting consolidation by GCP were prominent, and the mixed clay was not monitored in all of the three compaction piles.

• Geotechnical Engineering
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• v.3 no.1
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• pp.7-24
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• 1987

Preloading surcharge method along with vertical drains was adopted to improve the performance of a very soft marine clay deposit. The onshore deposit, located in the Ulsan Bay area, consists of a 2 to 10m thick, very soft, highly compressible marine clay layer developed just below. the sea water level. The initial undrained shear strength of the clay layer was about 0.6 ton/m2. But, the deposit was designed after treatment to support some auxiliary facilities for a new ilo refinery plant, requiring bearing capacities of 3.6 to 5.4 ton/m2 and maximum allowablee settlement of less than 7.5cm. A total of 35, 000 wick drains Ivas installed to expedite drainage during preloading, and surcharge loads of up to 5m above the original ground level were applied in a step-by-step loading sequence to prevent ground failure by excess surcharge loads. An extensive program of field instrumentation was implemented to monitor the behavior of the clay deposit. Measurers!ends included settlements, excess pore pressure and its dissipation, ground farmer level fluctuation, and lateral movement of the so(t clay layer under the preloads. This paper describes the design concepts, construction methods and control procedures used for improvement of the clay layer. It also presents the ground behavior measured during construction, rind comparisons with theoretical predictions.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.21-29
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• 2012

Ground failure by liquefaction can occur not only during shaking but also as the result of the post-liquefaction process after an earthquake. During the process of ground deformation and failure, excess pore water pressure in soil is redistributed, which can then lead to changes in the effective stress of soils. Therefore, in order to provide a further understanding of the phenomenon, we have to estimate the properties of effective stress during the recompression process in post-liquefaction as well, not only the total amount of pore water drained. The primary objectives of this study are to determine and compare the recompression properties in the post-liquefaction process in terms of the relationship between volumetric strains and mean effective stresses under the various conditions of relative density and shear stress history. In all experimental cases, the volumetric strains increase greatly in the low effective stress level, almost to the zero zone, and granite soil, which has fine grains, undergoes gradual changes in the relationship between volumetric strains and mean effective stresses compared with fine sand. And, we can also find that recompression properties in the post-liquefaction process by cyclic loading depend highly on the dissipation energy and maximum shear strain, and this fact can be obtained in all cases regardless of the existence of fine content, relative density, and loading history. Especially, granite soil having fine grains can be defined uniformly in the relationship between dissipation energy and maximum volumetric strain, while fine sand cannot be so uniformly defined.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.87-96
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• 2002

The strain holding test(SHT) or the sell-boring pressuremeter test(SBPT) has been effectively utilized to determine the horizontal coefficient of consolidation$(c_h)$ of clayey soils. However, a commonly used procedure proposed by Clarke et al.(1979) can lead to an erroneous estimation of $(c_h)$ because of its simplified assumptions. This paper deals with numerical analyses based on realistic test conditions of the generally accepted testing procedure, and .using the most commonly used type of pressuremeter. The effects of pressuremeter geometry, partial drainage during cavity expansion, and the cavity strain level for the holding test are investigated with the radial distributions of the initial excess pore pressure and their dissipation rate. Based on the results of the numerical analyses, the curve of the time factor for the 50% degree of consolidation($T_{50}$) needed to estimate $(c_h)$ is proposed. Comparisons are made between $(c_h)$ values estimated from the SHT or the SBPT and those obtained from other in situ and laboratory tests performed at two sites in Korea. These results suggest the improved capability of the $T_{50}$ curve proposed herein.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.17-23
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• 2003

Accurate prediction of consolidation behaviors of the soft ground improved by plastic board drains is not easy because the consolidation characteristics of the improved ground has not been fully elucidated yet. The shape of drains is one of the most important factors which affect the consolidation characteristics of the improved ground. In this paper, a series of model consolidation tests of soft clay ground improved by plastic board drain were carried out, in order to investigate the effect of both plastic board width and stress level on consolidation characteristics of the improved ground. As the results, behaviors of both settlement and excess pore pressure dissipation were elucidated. Also, the non-uniform distribution of water content in the model ground was obtained. Then, in order to investigate the effect of vertical drainage on the consolidation behavior in the model tests, the comparison between experimental consolidation behaviors and Barron's theoretical ones were carried out. As the results, it was elucidated that the consolidation behavior in the model tests was affected not only by radial drainage but also by vertical drainage.