• 제목/요약/키워드: consolidation pressure ratio

검색결과 126건 처리시간 0.02초

준설매립토지반의 압밀침하량 예측 (Prediction of Consolidational Settlement of Dredged and Reclaimed Ground)

  • 유남재;박병수;정길수
    • 산업기술연구
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    • 제21권A호
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    • pp.317-327
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    • 2001
  • For soils with high void ratios, the inverse method of utilizing results obtained from centrifuge model test was used to find the constitutive relation of effective stress - void ratio - permeability whereas conventional oedometer test and constant rate of strain consolidation test were also used to fine its relation at ranges of relatively low void ratio. Results of column test about settlement of interface and pore pressure and distribution with time were compared with numerically estimated values to confirm such a constitutive relation as obtained from the inverse method. Consolidational settlement in dredged and reclaimed ground, where the consolidation was in progress, was predicted by using the numerical technique implemented with the finite strain consolidation theory.

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음적차분해석법을 이용한 연직배수 공법에 의한 압밀침하에 관한 연구 (A Study on the Consolidation Settlement Due to the Vertical Drain Method by the Implicit Finite Difference Scheme)

  • 박성재;정두회;정경환;이경준
    • 대한토목학회논문집
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    • 제14권5호
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    • pp.1243-1251
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    • 1994
  • 연직드레인의 유효반경내에서 시간과 압밀도 관계를 계산하기 위해 음적차분해법이 적용되었으며 계산시 과잉간극수압의 소산은 두 방향으로 수행된다. 다단계 성토에 의한 지중응력 증분을 계산하기 위해, 지표면하의 연약지반은 등방균질 탄성체로서 간주하였고 각 단계 순간성토시 초기 과잉간극수압은 포화된 점성토내에서 평면변형률 조건과 탄성단계의 간극수압 응답 상태에 대한 Skempton의 간극수압계수를 이용해 계산하였다. 침하에 대해서는, 즉시 및 1 차 압밀침하량만 계산하였고, 2차 압밀침하는 고려하지 않았다. 계산된 과잉간극수압과 지표침하량이 경과시간에 대한 현성측성치와 유사한 것으로 판정되었으며, 본 연구에 적용된 계산기법(압밀특성이 다른 다층지반으로 구성된 연약지반내에 연직배수공법을 적용하고 성토가 다단계 순간성토로 이루어질 경우 과잉간극수압 소산과정을 음적 차분해법으로 근사계산)은 각 연약층의 시간-압밀도 관계를 예측하는데 이용가능할 것으로 생각된다.

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수치해석을 통한 샌드드레인과 열주입에 의한 연약지반의 압밀 해석 (Numerical Analysis on Consolidation of Soft Clay by Sand Drain with Heat Injection)

  • 고이 잔나릿;윤찬영
    • 한국지반공학회논문집
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    • 제33권11호
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    • pp.45-57
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    • 2017
  • 연약지반의 압밀거동은 온도변화에 의하여 영향을 받는다. 연약 점토지반 내에 온도가 증가하면 간극수압이 증가하고 간극수압의 소산은 부피와 간극비를 감소시킨다. 또한 높은 온도는 간극유체의 점성을 감소시키므로 압밀속도가 빨라진다. 본 연구에서는 온도가 압밀침하량, 압밀시간, 간극수압과 같은 압밀거동에 미치는 영향을 분석하였으며, 이를 위하여 수리역학적(HM) 및 열수리역학적(THM) 거동에 대한 수치해석을 수행하였다. 열주입과 샌드드레인을 동시에 고려하였으며, 온도 변화 및 샌드드레인 직경 변화를 고려하여 해석을 수행하였다. 해석결과, 시료내부의 온도는 열원의 온도와 샌드드레인의 직경 증가에 따라 증가하는 것으로 나타났다. 또한 열주입은 과잉간극수압을 증가시키고 그에 따라 과압밀 영역에서는 추가적인 침하량을 유발하고 정규압밀 영역에서는 압밀시간을 감소시키는 것으로 나타났다.

Aging Effect를 고려한 점성토의 압밀특성 (Consolidation Characteristics of Clays Considering the Aging Effect)

  • 김영수;이상웅;김대만;현영환
    • 한국지반공학회논문집
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    • 제20권6호
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    • pp.109-118
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    • 2004
  • 점토의 압밀은 시간적 지연을 갖는 현상으로 시간적 지연은 소성적 지연시간과 수리적 지연시간으로 나눠진다. 본 연구에서는 점토의 2차압밀이 압밀침하에 어떠한 영향을 미치는지를 알고자 CRS 시험을 실시하였다. 시험결과 소성적 지연시간은 선행압밀하중을 구하는데 큰 영향을 미치는 것으로 나타났고, 압밀하중과 압밀지연시간으로부터 유사선행압밀하중을 예측하는 식을 제안하였다. 또 압밀지연시간에 따른 압밀계수의 특징은 선행압밀 전까지는 큰 범위의 값을 가지나 선행압밀하중의 약 2배 지점을 지나서는 압밀지연시간에 관계없이 일정한 값으로 수렴하는 경향을 나타냈다. 그리고 정규압밀영역에서의 투수계수는 간극비와 밀접한 관계에 있으며, Samarasinghe 등의 제안식을 이용하여 시험결과로부터 투수상수 n, $C_1$값을 결정하였고, Kozeny-Carman 제안식과 비교분석하여 보았다. 투수계수와 간극비 관계에서도 압밀지연시간에 의한 지연압축으로 인하여 aging effect를 관찰할 수 있었다.

One-dimensional nonlinear consolidation behavior of structured soft clay under time-dependent loading

  • Liu, Weizheng;Shi, Zhiguo;Zhang, Junhui;Zhang, Dingwen
    • Geomechanics and Engineering
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    • 제18권3호
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    • pp.299-313
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    • 2019
  • This research investigated the nonlinear compressibility, permeability, the yielding due to structural degradation and their effects on consolidation behavior of structured soft soils. Based on oedometer and hydraulic conductivity test results of natural and reconstituted soft clays, linear log (1+e) ~ $log\;{\sigma}^{\prime}$ and log (1+e) ~ $log\;k_v$ relationships were developed to capture the variations in compressibility and permeability, and the yield stress ratio (YSR) was introduced to characterize the soil structure of natural soft clay. Semi-analytical solutions for one-dimensional consolidation of soft clay under time-dependent loading incorporating the effects of soil nonlinearity and soil structure were proposed. The semi-analytical solutions were verified against field measurements of a well-documented test embankment and they can give better accuracy in prediction of excess pore pressure compared to the predictions using the existing analytical solutions. Additionally, parametric studies were conducted to analyze the effects of YSR, compression index (${\lambda}_r$ and ${\lambda}_c$), and permeability index (${\eta}_k$) on the consolidation behavior of structured soft clays. The magnitude of the difference between degree of consolidation based on excess pore pressure ($U_p$) and that based on strain ($U_s$) depends on YSR. The parameter ${\lambda}_c/{\eta}_k$ plays a significant role in predicting consolidation behavior.

Geotechnical characteristics and consolidation properties of Tianjin marine clay

  • Lei, Huayang;Feng, Shuangxi;Jiang, Yan
    • Geomechanics and Engineering
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    • 제16권2호
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    • pp.125-140
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    • 2018
  • Tianjin, which is located on the west shore of the Bohai Sea, is part of China's Circum-Bohai-Sea Region, where very weak clay is deposited. From the 1970s to the early $21^{st}$ century, Tianjin marine clay deposits have been the subject of numerous geotechnical investigations. Because of these deposits' geological complexity, great depositional thickness, high water content, large void ratio, excessive settlement, and low shear strength, the geotechnical properties of Tianjin marine clay need to be summarized and evaluated based on various in situ and laboratory tests so that Tianjin can safely and economically sustain more infrastructure in the coming decades. In this study, the properties of Tianjin marine clay, especially its consolidation properties, are summarized, evaluated and discussed. The focus is on establishing correlations between the geotechnical property indexes and mechanical parameters of Tianjin marine clay. These correlations include the correlations between the water content and the void ratio, the depth and the undrained shear strength, the liquid limit and the compression index, the tip resistance and the constrained modulus, the plasticity index and the ratio of undrained shear strength and the preconsolidation pressure. In addition, the primary consolidation properties of Tianjin marine clay, such as the intrinsic compression line (ICL), sedimentation compression line (SCL), compression index, $C_c$, coefficient of consolidation, $C_v$, and hydraulic conductivity change index, $C_{kv}$, are evaluated and discussed. A secondary consolidation property, i.e., the secondary compression index, $C_a$, is also investigated, and the results show that the ratio of $C_a/C_c$ for Tianjin marine clay can be used to calculate $C_a$ in secondary consolidation settlement predictions.

이탄토의 반복압밀특성 (Consolidation Characteristics of Repeated Loading for Peat)

  • 김재영;주재우;박성희
    • 한국농공학회:학술대회논문집
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    • 한국농공학회 2001년도 학술발표회 발표논문집
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    • pp.379-385
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    • 2001
  • A series of standard consolidation tests and repeated loading consolidation tests were peformed with 2 kinds of peat sampled in Chonbuk area to study the consolidation characteristics of peat. The samples had following physical properties : 58% and 72% of organic content, 487% and 685% of natural moisture content and 7.02 and 9.72 of initial void ratio, respectively. And compression index $C_{c}$ and coefficient of secondary consolidation $C_{\alpha}$ were increased steeply when the consolidation load exceed about 2.5 and 3 times of each preload as like the characteristics of peat. The dependance on consolidation pressure of $C_{C}\;and\;C_{\alpha}$ in peatl and the maximum values, 2.9-3.8 and 0.3-0.4 were larger than that of normal clay, respectively.

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상재하중에 의한 연약점토의 일차원 압밀에 관한 원심모형실험 (Centrifuge Model Experiments on One-dimensional Consolidation of Soft Clay with Surcharges)

  • 유남재;이명욱;이종호
    • 산업기술연구
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    • 제17권
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    • pp.103-110
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    • 1997
  • This thesis is to investigate the one-dimensional consolidation behavior of soft marine clay with uniform surcharges by perfoming numerical and experimental works. Parametric experimental works of centrifuge model test were carried out changing test conditions of gravitational level in centrifuge, magnitude of surcharges and construction sequence of applying surcharges. Results of centrifuge model experiments were analyzed by using the numerical technique of explicit finite difference method based on the finite strain consolidation theory, being known to be appropriate to analyze the consolidational behavior of soft clay with a very high initial void ratio using the Lagrangian and the material coordinate systems. Test results were in relatively good agreements with analyzed results in terms of excess pore pressure dissipation and consolidation settlement with time and final void ratio distribution.

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실트질 함유량에 따른 낙동강 모래의 비배수 반복전단거동 특성 (Characteristics of Undrained Cyclic Shear Behavior of Nak-Dong River Sand by Silt Contents)

  • 김영수;김대만
    • 한국지반공학회논문집
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    • 제24권11호
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    • pp.79-89
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    • 2008
  • 본 연구에서는 낙동강 유역에 분포하는 모래와 실트를 대상으로 실트 함유량에 따른 모래의 비배수 반복전단강도 특성을 파악하기 위하여 이방압밀비($K_c$=1.0, 1.5, 2.0)를 달리하여 일련의 비배수 반복삼축시험을 실시하였다. 시험결과 모든 $K_c$에서 실트 함유량이 증가함에 따라 반복전단응력비(CSR)가 감소하였으며, $K_c$가 증가할수록 실트 함유량 증가에 의한 CSR의 감소가 더 크게 나타났다. 전단시 발생되는 과잉간극수압은 $K_c$에 관계없이 실트 함유량 증가에 따라 초기 과잉간극수압이 크게 발생되어 CSR의 감소에 영향을 미쳤으며, 또한 압밀 후 시료의 skeleton 간극비를 산정하여 분석한 결과 실트 함유량 증가에 비례하여 전반적으로 skeleton 간극비가 크게 증가하여 초기 과잉간극수압의 증가와 더블어 CSR 감소의 주요원인으로 파악되었다.

정지토압계수 측정에 관한 연구 1 (A Study on the Measuring about the Coefficient of Earth Pressure at Rest 1)

  • 송무효
    • 한국해양공학회지
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    • 제15권4호
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    • pp.92-100
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    • 2001
  • It is very important to determine the coefficient of earth pressure at rest accurately in order to estimate the behavior of soil structure. For estimation of K/sub 0/-value depending upon the stress history of dry sand, a new type of K/sub 0/-oedeometer apparatus is devised, and the horizontal earth pressure is accurately measured. For this study, 2 types of one-cyclic K/sub 0/-Loading/unloading models have been studied experimentally using four relative densities of the sand. The results obtained in this test are as follows : K/sub on'/ the coefficient of earth pressure at - rest for virgin loading is a function of the angle of internal friction Φ' of the sand and is determined as K/sub on/=1 - 0.914 sin Φ', K/sub ou'/ the coefficient of earth pressure at rest for virgin unloading is a function of K/sub on/ and over consolidation ratio(OCR), and is determined as K/sub ou/=K/sub on/(OCR)K/sup a/. The exponent α, increases as the relative density increases. K/sub or'/ the coefficient of earth pressure at rest for virgin reloading decreases in hyperbola type as the vertical stress, σ/sub v/’, increases. And, the stress path at virgin reloading leads to the maximum prestress point, independent upon the value of the minimum unloading stress. The gradient of this curve, m/sub r/ increases as OCR increases.

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