• Title/Summary/Keyword: 간극량

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Nonlinear Consolidation Analysis Considering Radial Drainage (수평배수를 고려한 비선형 압밀해석)

  • Lee, Song;Chae, Young-Su;Hwang, Koou-Ho;Jeon, Je-Sung
    • 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.

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Evaluation of the Degree of Consolidation using Settlement and Excessive Pore Water Pressure (침하량과 간극수압에 의한 압밀도의 평가(지반공학))

  • 이달원;임성훈;윤제식;김지문
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2000.10a
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    • pp.444-450
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    • 2000
  • This study was performed to analyze the degree of consolidation by the dissipation of excessive pore water pressure and final settlement prediction methods of the very soft clay. Hyperbolic method, Asaoka method and curve fitting method were used to compute the degree of consolidation. The degree of consolidation with excessive pore water pressure were used to compute, which considered the dissipation time with embankment construction. The degree of consolidation that was obtained by the peak excessive pore water pressure was less than in the case of the dissipation excessive pore water pressure. And, the degree of consolidation by the total settlement was nearly the same value that of layer settlement. The degree of consolidation that was obtained by excessive pore water pressure was larger than in the case of the settlement.

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$C_a/C_c$ for Marine Clay at Southern Part of Korea by Laboratory Consolidation Tests (실내압밀시험에 의한 남해안 해성점토의 $C_a/C_c$)

  • 김규선;임형덕;이우진
    • Journal of the Korean Geotechnical Society
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    • v.15 no.6
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    • pp.87-98
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    • 1999
  • Consolidation settlements on soft clay are often greatly and potentially damaging to structures. Currently, large-scale projects are in planning or progressing in Korea. These structures will be constructed on both thick and soft clay layers, and so the accurate evaluation of magnitude of settlement is required at every step in design and construction. Especially, secondary compression may play an important role in consolidation settlements of soft clay. Generally, the magnitudes of secondary compression are evaluated by laboratory and in-situ consolidation tests. The empirical $C_a/C_c$ may be economical, fast and powerful tool in estimating secondary consolidation settlement. However, the databases of the $C_a/C_c$ at construction site in Korea are insufficient. The purpose of this study is to investigate the relationship of $C_a/C_c$ on marine clay near the southern sea in Korea. A series of incremental loading consolidation tests (measuring base pore water pressure) is peformed. It was found that the $C_a/C_c$ on undisturbed marine clay is 0.0397.

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A Consideration on Deformation Characteristics of Normally-Consolidated Clays by Various Stress Paths (다양한 응력경로에 따른 정규압밀 점성토의 변형특성 고찰)

  • 김창엽;정충기
    • Journal of the Korean Geotechnical Society
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    • v.15 no.1
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    • pp.161-173
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    • 1999
  • Settlement analysis based on oedometer test results with or without Skempton-Bjerrum's modification method ( widely used for practical purposes when estimating consolidation settlements of soft clay deposits) has shortcomings that it cannot simulate real stress states and deformation behaviors of soils in case that in-situ loading and deformation conditions are not 1-dimensional. In this study, the stress path method, reflecting various probable stress paths, was employed to normally - consolidated kaolinite samples by using automated triaxial testing device which can control stress paths automatically. From this experimental study, elastic, consolidation, secondary compression and pore pressure development - dissipation behaviors under various stress paths were analyzed and deformation characteristics of soft clays, which can be the basis of rational estimation of settlements, were studied. Also by comparing results of stress path tests with those of 1-dimensional consolidation tests, limitations and problems of conventional methods were clarified.

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The Analysis for the Effect of Effective Compressibility on Oil Recovery in Polymer Flooded Heterogeneous Reservoir (폴리머 공법 적용 불균질 저류층에서의 유효 압축률이 오일생산에 미치는 영향 분석)

  • Baek, Soohyun;Jung, Woodong;Sung, Wonmo;Seo, Junwoo
    • Economic and Environmental Geology
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    • v.47 no.3
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    • pp.247-254
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    • 2014
  • The compressibility of fracture in naturally fractured reservoir is larger than the compressibility of matrix in rock, although the compressibility of a typical rock is very small. The effective compressibility including the fracture compressibility should be considered to predict oil recovery correctly. It is hard to quantify changes of fracture aperture and pore volume in reservoir without the effective compressibility. In this study, oil recovery is analyzed by commercial simulator concerning the fracture compressibility based on fracture properties. We found that the effective compressibility affects oil recovery with change of polymer flooding factors such as polymer molar weight, concentration and injection rate. The estimated cumulative oil production is smaller with the effective compressibility than without it. Also, bottomhole pressure decreases rapidly without considering effective fracture compressibility.

Case Study of Characteristics on Lateral Deformation in Soft Ground under Embankment in the Nakdong River Estuary(I) (낙동강 하구지역 성토하부 연약지반의 측방변형 특성에 관한 사례 연구(I))

  • Han, Byung-Won;Son, Hwa-Soo;Sung, In-Chool;Baek, Young-Gyun;Lee, Gay-Chun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.1178-1189
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    • 2010
  • 낙동강 하구지역 연직배수공법이 적용된 연약지반에서 성토시 발생할 수 있는 지반의 측방변형에 대해 3개소 현장 35개 지점에서 수행한 현장 계측데이터를 분석하였다. 성토과정에서 측방변형 패턴 및 변형량을 파악하는데 가장 우선적으로 파악해야 할 계측항목이 지중경사계이며 지반특성별 측방변형 패턴(최대 측방변위발생 지점, 전단변위 발생지점, 지층에 따른 변위발생 형태 등)의 정밀 분석을 위해서는 지중경사계가 설치된 지점의 지층구성을 파악하는 것이 가장 중요하다는 것을 알 수 있었다. 최대 측방변위량과 성토체 중앙부 침하량과의 관계에서는 Tavenas et al.(1979)이 제안한 ${\Delta}_y=(0.18+0.09){\Delta}_s$이하로 관측되었다. 또한 측방변형 억제 및 인접지반의 동반침하를 차단하기 위해 보강된 D.C.M., C.I.P.구간에서는 Tavenas et al.(1979)이 제안한 ${\Delta}_y=(0.18-0.09){\Delta}_s$이하로 관측되었다. 최대 측방변위량과 성토속도와의 관계에서는 과잉간극수압 소산에 필요한 충분한 시간과 원활한 배수가 될 수 있도록 시공관리(성토속도조절, 배수관리 철저)하는 것이 무엇보다도 중요하다는 사실을 다시 한 번 확인 할 수 있었다. 마지막으로 편재하중 재하에 따른 인접 지반 및 구조물의 침하 및 기울기 변화는 측방유동에 의한 거동과 함께 압밀침하에 의한 제체의 체적감소로 인한 인접지반의 동반침하가 상당기간 동안 발생하고 있는 것으로 관측되었다.

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study of the character and condition of Cr in the korea cement (국내 시멘트 중의 크로뮴 성상에 관한 연구)

  • Min, Kyung-San;Lee, Seung-Heun;Lee, Se-Jin;Lee, Seung-Hoon;Moon, Se-Heum;Jeong, Jae-Hong
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.521-524
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    • 2008
  • The purpose of this study is to identify the character and condition of Cr in the clinker and thereby contribute to the research for reduction in utilizing Cr in the cement manufacturing process. The concentration of chromium by cement particle size and the distribution of chromium by clinker mineral were measured. Next, correlation was considered between chromium and the soluble components in cement. As a result, in the range that cement particles were 20${\mu}$m or less, highest soluble hexavalent chromium was found. When the concentration of chromium was measured through mineral separation, belite and the interstitial phase were higher in chromium than in alite. soluble hexavalent chromium was contained in domestic cement less than 20ppm, and its conversion ratio was somewhat high as 10 to 40% or so.

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The Experimental Study on the Long-term Creep Settlements of Nam-Hae Sands (남해안 모래의 장기 크리프 침하 특성에 관한 실험적 연구)

  • Park, Eonsang
    • 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.

Effect of Cyclic Freezing-Thawing on Compressive Strength of Decomposed Granite Soils (동결-융해 반복작용으로 인한 화강풍화토의 압축강도 특성 변화에 관한 연구)

  • Yoo, Chung-Sik;Shin, Boo-Nam
    • Journal of the Korean Geosynthetics Society
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    • v.10 no.1
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    • pp.19-28
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    • 2011
  • This paper presents the results of an investigation into the effect of cyclic freezing-thawing on the compressive strength characteristics of decomposed granite soils. A plane strain compression (PSC) tests were performed on a series of test specimens with different freezing-thawing cycles and fine contents to investigate the change in compressive strength under the process of freezing-thawing cycles. Also performed were scanning electron microscope (SEM) tests to investigate the change in structural rearrangement from a micro-scale point of view. The test results showed that the soil particles tend to conglomerate when subject to cycles of freezing and thawing, and that the soil with less fines exhibited decreased shear strength due to the cyclic freezing-thawing while the soils with a larger fine content showed the opposite trend.

Numerical study for the optimum grouting design of subsea tunnels (해저터널의 그라우팅 최적 설계를 위한 수치해석적 연구)

  • Joo, Eun-Jung;Kim, Yong-Kye;Shin, Jong-Ho;Kwon, Oh-Yeob
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.5
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    • pp.349-358
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    • 2010
  • In the long-term, most tunnels suffer from the increase in ground water inflow and in pore water pressure on the lining. To reduce such hydraulic effect, generally grouting methods are adopted. In this paper effective grouting design is proposed based on numerical simulation. To investigate the optimal grouting layout, factors such as relative permeability, grouting thickness, and distance from the lining are considered. The results are analysed in terms of pore water pressure, inflow rate, and earth pressure. It is revealed that the pore water pressure has increased with a decrease in grout permeability, an increase in grouting thickness and an increase in grouting distance. Meanwhile the inflow rate has decreased with a decrease in grout permeability and is inversely proportional to grouting thickness. Effective grouting design guideline are proposed based on this study.