• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.463-465
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• 2005

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.153-160
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• 2001

피에조콘관입시험(PCPT)의 소산시험은 in-situ 상태의 압밀계수(c/sub v/)를 추정하는 방법으로 널리 이용되어왔다. 본 연구에서는 spherical cavity expansion theory 및 axisymmetric uncoupled linear consolidation equation(Gupta & Davidson, 1986)을 이용하여 과압밀점토에서의 초기과잉간극수압의 분포 및 과잉간극수압의 시간에 대한 소산현상을 해석하는 수치해석방법을 제안하여 현장시험결과 및 실내시험결과와 비교 분석하였다. ADIS (alternating direction implicit scheme)를 이용한 FDM 해석을 실시한 결과와 현장시험의 소산곡선은 잘 부합되는 것으로 나타났으며 압밀계수도 실내실험 또는 피에조콘관입 시험에 대한 추정방법으로 산출된 값과 비교적 일치하는 것으로 나타났다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.10a
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• pp.158-160
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• 2006

• Geotechnical Engineering
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• v.13 no.4
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• pp.95-108
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• 1997

For normally consolidated clay, several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation However, depending on the assumptions and analytical techniques, it could considerably vary even for a specific degree of consolidation. In this paper, a method is proposed to determine a consistent coefficient of consolidation over all ranges of degree of consolidation by applying the concept of the Optimum Design Technique. The initial excess pore pressure distribution is assumed to be obtainable by the successive spherical cavity expansion theory. The dissipation of pore pressure is simulated by means of two dimensional linear-uncoupled axisymmetric consolidation analysis. The minimization of the differences between the measured and the predicted excess pore pressures was carried by BFGS unconstrained optimum design algorithm with one dimensional golden section search technique. By analyzing numerical and real field examples, it can be found that the adopted optimum technique gives a consistent and convergent results.

• Geotechnical Engineering
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• v.14 no.4
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• pp.141-150
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• 1998

Based on the authors' previous research, we have conducted more researches on finding out the coefficient of consolidation from Piezocone dissipation test results, especially measured behind the cone tip which is mostly used in Korea, by adopting the optimization technique. By analyzing numerical and real field examples, it can be found that the adopted optimum technique that minimizes the differences between the predicted dissipation curve and the measured one gives consistent and convergent results, irrespective of initial values. Such technique also provides horizontal coefficient of consolidation which is able to simulate real field consolidation behavior more effectively.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.349-359
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• 2011

The consolidation behavior of soft clay is controlled mainly by its compressibility and deformation characteristics. Soil permeability depends on various soil characteristics, including the soil type and anisotropy. The coefficient of permeability of soft clay is determined by using a laboratory test (the Oedometer test) or a piezocone test. The latter test is useful for estimating the permeability characteristics from $c_h$ and $k_h$ by performing an excess pore-pressure dissipation test. This study seeks to validate an existing theoretical formula in applying it to marine clay, and to assess the relation between $k_h/k_c$ and the mechanical properties of soft clay. Piezocone tests and laboratory tests were performed using sediment from the Yellow Sea and from the South Sea near Korea. We compared $k_h/k_v$ values obtained using the piezocone test and using laboratory consolidation tests. The obtained values are similar to the values obtained by Jamiolkowski et al. (M application); therefore, the latter values are recommended to be used as $k_h/k_v$.

• 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).

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.13-22
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• 2000

서해안에 위치한 특정 연구현장에서 연약지반의 압밀거동을 파악하기 위한 소산시험을 포함한 콘관입시험을 수행했다. 연구현장에서 시험시공으로 적용한 연약지반개량공법으로는 압성토공법, 두 종류의 페이퍼드레인 공법, 팩드레인 공법이었으며 각각의 공법들에 있어 현장에서의 지반개량에 따른 압밀거동을 판정하기 위해서 적용되었다. 콘관입시험은 근본적으로 지반개량 전과 후에 보링, 표준관입시험, 압밀시험과 함께 수행되었다. 실내실험과 피조콘관입시험을 비교한 결과, 연약지반의 표층에서는 상당한 지반개량효과가 있었으나 표층아래 심층지반에서는 그렇치 않았다. 그리고 지반개량 후, 10개월이 지난 시점에 압밀시험과 소산시험 결과를 통하여 분석한 수평압밀계수는 압성토 방법을 제외한 3가지 개량공법을 적용한 지점에서 압밀계수는 감소하여 개량효과를 간접적으로 판단할 수 있었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.142-147
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• 2020

This study investigates the effects of moisture content on diffuse ultrasound to be applied for the evaluation of micro-structural damage in concrete subjected to various environmental conditions. We monitored diffuse wave parameters for concrete samples in process of water saturation for 5 days. Dried samples were immersed in a water bath, and the change of moisture content in concrete were estimated by measuring the change of mass. For the diffuse wave analysis, a frequency range of 500 kHz, which represents a scattering regime of ultrasound in concrete, was selected. The test results reveal that the ultrasonic diffusivity slightly changed, and the ultrasonic dissipation significantly increased by approximately 120% in the process of water saturation. Therefore, the moisture content in concrete should be considered for the evaluation of micro-structural damage using diffuse wave techniques.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.39-48
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• 2001

액상화 발생후 과잉간극수압 소산 특성을 파악하기 위하여 포화된 수평 모래지반에 대하여 1-g 진동대시험을 수행하였다. 진동대시험에는 주문진 표준사와 영종도 세사를 사용하였으며 상대밀도를 dir 20~30% 사이가 되도록 조성하였다. 간극수압계, 가속도계 그리고 LVDT 등으로 시험중의 지반거동을 계측하였으며, 4Hz의 sine 파를 0.15g에서 5초간 5회 반복하여 작용시켰다. 진동대시험을 분석한 결과 액상화 발생후 과잉간극수압의 소산속도는 그 지반의 투수성뿐 아니라 과잉간극수압 소산시 입자의 침강거리와 직접 관련이 있는 지반의 침하량에도 크게 영향을 받는 것으로 나타났으며, 이 과정을 침강모래 이론으로 모델링하였을 때 입자의 침강속도와 투수계수 사이의 비례 관계는 침강모래 이론에서의 가정한 것과는 달리 모래의 종류에 따라 차이를 나타내었다. 또한 Terzaghi의 압밀이론으로는 액상화 후 과잉간극수압의 소산과정을 적절히 모사할 수 없었다.