• Geomechanics and Engineering
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• 제25권2호
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• pp.159-170
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• 2021

Particle size of tailings in different areas of dams varies due to sedimentation and separation. Saturated hydraulic conductivity of high-stacked talings materials are seriously affected by void ratio and particle breakage. Conjoined consolidation permeability tests were carried out using a self-developed high-stress permeability and consolidation apparatus. The hydraulic conductivity decreases nonlinearly with the increase of consolidation pressure. The seepage pattern of coarse-particle tailings is channel flow, and the seepage pattern of fine-particle tailings is scattered flow. The change rate of hydraulic conductivity of tailings with different particle sizes under high consolidation pressure tends to be identical. A hydraulic conductivity hysteresis is found in coarse-particle tailings. The hydraulic conductivity hysteresis is more obvious when the water head is lower. A new hydraulic conductivity-void ratio equation was derived by introducing the concept of effective void ratio and breakage index. The equation integrated the hydraulic conductivity equation with different particle sizes over a wide range of consolidation pressures.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.725-732
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• 2003

It was achieved that Rowecell test for this undisturbed sample was picked by Block sampler($\phi$:250mm, L:500mm) and hydraulic piston sampler($\phi$:76mm, L:850mm) in the marine clay of YONGYUDO and YEONGJONGDO in this research. Ratio of coefficient of consolidation was analyzed through comparison with C$\_$h/ by CPTu and C$\_$v/ and C$\_$h/ by existent consolidation test. According to analysis, coefficient of consolidation of block sample is fairly greater than coefficient of consolidation of piston sample. And the bigger diameter of undisturbed sample, sample disturbance could know decreasing. Coefficient of consolidation by Rowecell test measured more greatly than coefficient of consolidation by existent consolidation test. Rowecell test could know decreasing consolidation rate because of smear effect by Mandrel injection. Also, C$\_$h/ by CPTu shows deviation by each analysis method, selection of suitable analysis method judged by important leading in the coefficient of consolidation.

• Geomechanics and Engineering
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• 제6권6호
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• pp.577-592
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• 2014

The methods for estimating in-situ hydraulic conductivity ($k_{hp}$) and coefficient of consolidation ($c_{hp}$) in the horizontal direction from piezocone penetration and dissipation test results have been investigated using test results at two sites in Saga, Japan. At the two sites the laboratory values of hydraulic conductivity ($k_v$) and coefficient of consolidation ($c_v$) in the vertical direction are also available. Comparing $k_{hp}$ with $k_v$ and $c_{hp}$ with $k_v$ values, suitable methods for estimating $k_{hp}$ and $c_{hp}$ values are recommended. For the two sites, where $k_{hp}{\approx}k_v$ and $c_{hp}{\approx}2c_v$. It is suggested that the estimated values of $k_{hp}$ and $c_{hp}$ can be used in engineering design.

• Geomechanics and Engineering
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• 제35권4호
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• pp.385-393
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• 2023

To analyze the consolidation with horizontal sand drains, the plane strain consolidation model under multi-ramp loading is established, and its corresponding analytical solution is derived by using the separation of variables method. The proposed solution is verified by the field measurement data and finite element results. Then, the effects of the loading mode and stress distribution on consolidation and dissipation of pore pressure are investigated. At the same time, the influence of hydraulic conductivity and thickness of sand blankets on soil consolidation are also analyzed. The results show that the loading mode has a significant effect on both the soil consolidation rate and generation-dissipation process of pore water pressure. In contrast, the influence of stress distribution on pore pressure dissipation is obvious, while its influence on soil consolidation rate is negligible. To guarantee the fully drained condition of the sand blanket, the ratio of hydraulic conductivity of the sand blanket to that of clay layer k_d/k_v should range from 1.0×10⁴ to 1.0×10⁶ with soil width varying from 100 m to 1000 m. A larger soil width correspondingly needs a greater value of kd/kv to make sure that the pore water can flow through the sand blanket smoothly with little resistance. When the soil width is relatively small (e.g., less than 100 m), the effect of thickness of the sand blanket on soil consolidation is insignificant. And its influence appears obvious gradually with the increase of the soil width.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.109-116
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• 1999

This study is to make clear for the characteristics of radial drainage consolidation/permeability At the result of the radial drainage consolidation / permeability test, the permeability of outflow drainage condition is higher than Inflow drainage condition and the time for the end of consolidation, outflow drainage condition is shorter than inflow drainage condition. So drainage area ratio test and control of hydraulic gradient test are carry out to analysis this result. Finally, compared with the characteristics on the condition of inflow and outflow permeability and consolidation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.520-527
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• 2000

In the present study, the analytical approaches of vacuum consolidation with horizontal drains were proposed, For dissipating rapidly pore-water in hydraulic fills, vacuum consolidation method applied vacuum pressure in horizontal drains is developed. In the analytical approaches, the governing equation is based on two-dimensional finite strain consolidation theory and the boundary conditions of horizontal drains are considered in applying negative pore-water pressure occurred by vacuum pressure, Also, parametric studies to vacuum pressure and installation pattern of horizontal drains are carried out.

• 한국지반공학회논문집
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• 제15권2호
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• pp.129-138
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• 1999

본 연구는 준설매립 점성토 지반의 토질정수를 효과적으로 구할 수 있는 자중 및 침투압밀시첨 기법과 현장 모형 실험장치의 개발을 중심으로 수행되었다. 이러한 모형 실험장치와 시험기법개발은 연약한 매립 지반의 침강-자중-재하압밀 과정에 대한 재현을 가능케하였다. 이러한 실험적 연구는 준설 점성토 지반의 자중압밀특성을 중심으로 이루어졌으며, 이론적인 연구로 매립점토 지반의 압밀해석시 Terzaghi의 1차원 압밀이론의 적용한계 등을 지적하였고, 이러한 문제점을 고려한 Mikasa의 자중 압밀이론을 토대로 유한차분해석을 실시하였다. 실내시험에 의해 군산 매립점토의 토질정수로 비체적-유효응력-투수계수 관계를 구하였으며 현장 모형실험을 통하여 투입단계부터 간극수압-토압-수위관계 및 침하량 등을 측정하였다. 시험에 의해 얻어진 결과는 Terzaghi의 방법과 Mikasa 자중압밀의 차분해석에 의해 비교.분석되었으며, 실측 침하량은 Terzaghi의 이론보다 Mikasa의 자중압밀이론이 비교적 잘 일치하였다.

• 한국지반공학회논문집
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• 제21권10호
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• pp.41-48
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• 2005

수평배수재가 설치된 준설매립지반의 중력에 의한 압밀 거동을 수평배수 자중압밀해석을 위하여 개발된 유한차분 프로그램을 이용하여 해석하였다. 수평배수재 단면의 크기와 수평배수재의 설치단면의 방향(수직/수평)이 대상지반의 압밀에 미치는 영향을 분석하였다. 또한 시공된 지반에서 발생 가능한 요인들, 즉 하부 무처리층의 존재, 그리고 수평배수재 단부에서의 수두적체 등이 압밀속도와 침하량에 미치는 영향도 분석하였다. 그 결과, 수평배수재의 단면적을 2배로 증가하여도 압밀 소요시간이 미량 감소하는데 그쳤으나, 수평배수재를 수직방향으로 설치한 경우 수평방향 설치시에 비하여 압밀소요 시간이 매우 감소하는 것으로 평가되었다. 해석결과로 부터 하부 무처리층의 영향이 처리 지반의 장기 침하에 미치는 영향이 크며, 배수재 단부에 발생하는 수두적체는 압밀시간 증가와 미진한 압밀효과를 초래하는 것을 정량적으로 알 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.353-360
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• 2000

We developed large diameter sampler (we called KICT type large diameter sampler) to obtain undisturbed clay and sand samples. In-situ test carried out in the In-Chon international airport and Kim-Hae. Also we obtained undisturbed sample with a hydraulic piston sampler in the nearly site and carried out unconfined compression test, consolidation test and triaxial test. The result, unconfined compression strength, secant modules, preconsolidation pressure and undrained shear strength of samples to obtain KICT type large diameter sampler are larger than that of samples to obtain hydraulic piston sampler. But failure strains and volume changes at the consolidation of samples to obtain KICT type large diameter sampler are smaller than that of samples to obtain hydraulic piston sampler

• Geomechanics and Engineering
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• 제8권2호
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• pp.187-220
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• 2015

Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.