• 한국지반환경공학회 논문집
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• 제9권2호
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• pp.5-13
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• 2008

본 연구에서는 원지반 상부에 분포하는 준설토 매립층으로 인한 원지반의 압밀이력을 분석하기 위해 다양한 현장 원위치 시험과 실내시험을 수행하였으며, 특히 준설매립하중에 의한 원지반 압밀이 완료되지 않은 경우 추가 성토하중 재하시 합리적인 침하량 산정을 위해 CPTu 시험을 수행하였다. 원지반의 CPTu 시험결과 준설매립하중에 의한 원지반 연약점토층의 압밀도는 평균 80%의 정도를 보였다. 연구대상지역은 과거 준설매립하중에 대하여 원지반의 압밀이 완료되지 않은 상태이므로 추가 성토하중 재하시 잔류 압밀도(20%)만큼의 잔류침하를 고려하여 압밀침하량을 산정하였다. 추가 성토하중(${\Delta}P_s$) 재하시 압밀진행중인 원지반의 잔류 압밀도를 고려하지 않는 경우 잔류 압밀도(20%)만큼의 잔류침하에 의해 과다한 침하가 예상되며, PBD공법에 의한 연약지반 개량시 소요 압밀도 확보가 어려운 것으로 나타났다.

• 산업기술연구
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• 제28권A호
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• pp.11-17
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• 2008

Applicability of hyperbolic settlement prediction method to consolidation settlement in the dredged and reclaimed ground was assessed by analyzing results of centrifuge tests modelling self-weight consolidation of soft marine clay. From literature review about self-weight consolidation of soft marine clays located in southern coast in Korea, constitutive relationships of void ratio - effective stress - permeability and typical self-weight consolidation curves with time were obtained by analyzing centrifuge model experiments. For the condition of surcharge loading, exact solution of consolidation settlement curve obtained by using Terzaghi's consolidation theory was compared with results predicted by the hyperbolic method. It was found to have its own inherent error to predict final consolidation settlement. From results of analyzing thc self-weight consolidation with time by using this method, it predicted relatively well in error range of 0.04~18% for the case of showing the linearity in the relationship between T vs T/S in the stage of consolidation degree of 60~90 %. However, it overestimated the final settlement with large errors if those relation curves were nonlinear.

• Geomechanics and Engineering
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• 제19권5호
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• pp.447-462
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• 2019

The vacuum preloading method has been used in many countries for ground improvement and land reclamation works. A sand cushion is required as a horizontal drainage channel for conventional vacuum preloading. In terms of the dredged-fill foundation soil, the treatment effect of the conventional vacuum preloading method is poor, particularly in Tianjin, China, where a shortage of sand exists. To solve this problem, straight-line vacuum preloading without sand is widely adopted in engineering practice to improve the foundation soil. Based on the engineering properties of dredged fill in Lingang City, Tianjin, this paper presents field instrumentation in five sections and analyzes the effect of a prefabricated vertical drain (PVD) layout and a vacuum pumping method on the soft soil ground treatment. Through the arrangement of pore water pressure gauges, settlement marks and vane shear tests, the settlement, pore water pressure and subsoil bearing capacity are analyzed to evaluate the effect of the ground treatment. This study demonstrates that straight-line vacuum preloading without sand can be suitable for areas with a high water content. Furthermore, the consolidation settlement and consolidation degree system is developed based on the grey model to predict the consolidation settlement and consolidation degree under vacuum preloading; the validity of the system is also verified.

• 한국지반공학회지:지반
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• 제14권6호
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• pp.93-112
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• 1998

본 연구에서는, 연약한 준설매립점토지반 내부에 플라스틱 배수재를 수평으로 설치하여 압밀침하의 가속화를 유도하는 수평배수공법의 해석절차 체계화에 초점을 두고 이론적 및 실험적 접근을 진행하였다. 이를 위해, 유한변형률 개념을 근거로 한 Gibson등의 1차원 자중압밀이론을 토대로, 자중압밀효과 및 수평배수재 설치에 따른 추가 압밀효과를 복합적으로 고려하는 지배방정식을 제시하였으며, 본 지배방정식 및 수평배수재 설치효과를 고려한 초기조건 및 경계조건 등을 토대로, Dufort-Erankel의 유한차분화 알고리즘을 이용해 시간경과에 따른 침하량 및 압밀도 등의 변화를 예측하기 위한 해석절차를 제시하였다. 또한 제시된 해석절차의 적용 타당성 확인을 위해, 안산 시화지구 준설매립점토 및 플라스틱 수평배수재를 이용한 실내모형실험을 실시하였다. 실내실험을 통해, 안산 시화지구 준설매립점토의 간극비-유효응력 관계 및 투수계수-간극비 관계 등을 정량적으로 정의하기 위한 기초자료를 획득 하였으며. 또한 시간경과에 따른 깊이별 침하량등을 측정하여 본 연구에서 제시된 해석절차에 의한 예측치와 비교.분석하였다. 이외에도 플라스틱 배수재 수평배수공법에 관련된 설계변수가 압밀침하등에 미치는 영향을 제시된 해석절차를 이용해 분석하였으며, 이 결과를 토대로 한 설계도표의 제시도 이루어 졌다.

• 산업기술연구
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• 제27권A호
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• pp.111-120
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• 2007

This paper is results of experimental research on the effect of application of similarity related to permeability of soil on the consolidation behavior as centrifuge modeling of consolidation is performed with the centrifuge model facility. In this research, the permeability of soil was controlled by changing the viscosity of porewater as the mixed water with glycerin was used during the centrifuge model experiments. The effect of drainage path on consolidation was investigated by installing the vertical drains. A serise of centrifuge model tests with conditions of single vertical and radial horizontal drainage were carried out. Kaolinite and Jumunjin standard sand were used as soft clay and surcharges respectively during tests. For testing condition of single vertical drainage considering similarity of permeability, it was found that consolidation with mixed porewater with glycerin was delayed in comparisons sons with test results with water only. For conditions of horizontal drainage with vertical drains, a low permeability by changing the viscosity of pore water resulted in delayed degree of consolidation at an initial stage of consolidation. But, it predicted not much differences in settlement as long as the consolidation time was sufficiently long enough to finish consolidation. Consequently, it was found that similarity in permeability should be considered to be critical for the case of centrifuge model experiments related to consolidation with long drainage path.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.685-692
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• 2000

Vertical drain used improvement soft clay is made of not only decreasing construction time but also increasing the ground strength during some decades. As, it is applied to improvement soft clay with vertical drain, it is designed by the result that is caused by oedemeter test ignored anisotropic of the ground related to consolidation conditions. When we are expected consolidation conditions, the most important factors is soil of compaction and water permeability. Above all, anisotropic of the ground permeability show the results which differ between vertical and radial drainage. Recently, We study for radial consolidation coefficient and permeability coefficient that utilized Rowe Cell Consolidation and permeability tester but, it dont use well because of not only a supply lack also difficulty of test. The paper experimented with searching anisotropic of the ground so there are Rowe Cell test, standard consolidation tester and modified standard consolidation test that have pohang's soft clay ground. Therefore, we find anisotropic of the ground and a tester of easy use more than before. We made a comparison test result between the devised tester and Rowe Cell tester, Also, we learned average degree of consolidation for partial penetrating vertical drains. We were found relations as effective stress-void and effective stress-permeability coefficient through those tests.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.823-830
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• 2004

Consolidation tests under various deformation modes were performed to investigate the effect of deformation modes on the coefficient of consolidation in the normally consolidated clay in remolded and undisturbed clay. The degree of soil anisotropy was evaluated using cross-anisotropic elasticity theory suggested by Graham et al.(1983). Experimental results showed that the vertical compressibility was larger than the horizontal compressibility by $12{\sim}21%$ for the remolded clay and by $23{\sim}60%$ for the undisturbed clay, respectively. The results of a series of consolidation tests under the specific deformation modes showed that the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 3 dimensional strain condition due to different deformation mode. Furthermore, the coefficient of consolidation under 1 dimensional vertical strain condition was larger than that under 1 dimensional horizontal strain condition by $40{\sim}60%$ in undisturbed clay, which clearly emphasized the significant effect of soil anisotropy on the rate of consolidation. Consequently, it can be concluded that the anisotropic deformation modes of soils, especially naturally deposited clays, should be taken into account for more accurate evaluation of the coefficient of consolidation.

• 한국지반공학회지:지반
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• 제13권4호
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• pp.95-108
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• 1997

피에조 콘의 소산시험을 이용한 정규 압밀 지반의 압밀계수 추정은 그간 많은 연구자들에 의하여 연구되어 왔으나 각 연구자들의 가정 사항과 해석 방법에 따라 특정한 압밀도에 대해서도 매우 넓은 범위의 이론적인 해들이 제시되어 왔다. 본 연구에서는 보다 현실적이면서 전 범위의 압밀도에 걸쳐서 일관성 있는 압밀계수를 구할 수 있도록 최적화 기법을 적용하였다. 콘 관입효과를 고려하기 위해 연속적인 구형 공동확장을 적용하므로써 이론적으로 얻어지는 간극수압의 분포와 관입 간극수압으로부터 초기 과잉간극수압의 분포를 결정하였으며 축대칭 선형비혼합 압밀이론을 사용하여 유발된 과잉간극수압의 소산효과를 모사하였다. 이와 같이 계산된 소산곡 선과 실제 계측된 소산곡선의 차이를 최소화시키기 위하여 비구속 최적화 알고리듬인 BFGS가 사용되었고 golden section 일차원 탐색법이 사용되었다. 검증 예제를 통하여 적용된 최적화 기법의 안정된 수렴성을 확인하였고 실제 예제에 적용함으로써 제안된 방법이 넓은 범위의 압밀도 범위에서 계측된 소산곡선과 잘 일치하는 압밀계수를 산정함으로써 매우 효과적임을 확인 할 수 있었다.

• 대한기계학회논문집A
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• 제26권5호
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• pp.813-821
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• 2002

Glass fiber reinforced PET matrix composite was manufactured by rapid press consolidation technique as functions of temperature, pressure and time in pre-heating, consolidation and solidification stages. The optimal manufacturing conditions for this composite were discussed based on the void content, tensile, interlaminar shear and impact properties. In addition, the levels of crystallinity with various manufacturing conditions were measured using differential scanning calorimetry to investigate the mechanical properties of this composite material as a function of crystallinity. Among many processing parameters, the mold temperature and the cooling rate after forming were found to be the most critical factors in determining the level of crystallinity and mechanical properties. The level of crystallinity affects the tensile properties to some degree. However, impact properties are affected much more. It also affects the degree of ductility, which determines the impact energy of this material.

• Geomechanics and Engineering
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• 제4권4호
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• pp.243-249
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• 2012

In the companion paper, the nonlinear consolidation of soft clays subjected to cyclic loading was analytically investigated. This paper reports the results of an experimental program conducted to verify some critical assumptions made in the analytical study. It, also, includes a numerical study carried out to examine the capability of the proposed theory to determine the consolidation characteristics of soft clays subjected to cyclic loading. Results show that the permeability of the soft clays does not significantly change during the cyclic loading. It is also shown that, compared to the Terzaghi's solution for a linear clay, the inherit nonlinearity of the clay tends to decrease the degree of consolidation due to the smaller rate of dissipation in the excess pore water pressure.