• Title/Summary/Keyword: soft deposit

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Optimum PVD installation depth for two-way drainage deposit

  • Chai, J.C.;Miura, N.;Kirekawa, T.;Hino, T.
    • Geomechanics and Engineering
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    • v.1 no.3
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    • pp.179-191
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    • 2009
  • For a two-way drainage deposit under a surcharge load, it is possible to leave a layer adjacent to the bottom drainage boundary without prefabricated vertical drain (PVD) improvement and achieve approximately the same degree of consolidation as a fully penetrated case. This depth is designated as an optimum PVD installation depth. Further, for a two-way drainage deposit under vacuum pressure, if the PVDs are fully penetrated through the deposit, the vacuum pressure will leak through the bottom drainage boundary. In this case, the PVDs have to be partially penetrated, and there is an optimum installation depth. The equations for calculating these optimum installation depths are presented, and the usefulness of the equations is studied by using finite element analysis as well as laboratory model test results.

Prediction and Measurement of Behaviour of Soft Soil Deposits (연약지반에서 예측 거동과 계측 결과 분석)

  • Kim, Yun-Tae
    • Proceedings of the Korean Geotechical Society Conference
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    • 2007.09a
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    • pp.351-362
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    • 2007
  • Predicted behaviour of a soft clay deposit in design stage is sometimes different from in-situ settlement and pore pressure measured during and after construction. In this paper, characteristics of settlement and pore pressure occurred in soft soil deposits were investigated briefly in order to get a better understanding of time-dependent viscoplastic behaviour and prevent geotechnical problems resulted from long-term settlement, differential settlement, etc.

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Free strain analysis of the performance of vertical drains for soft soil improvement

  • Basack, Sudip;Nimbalkar, Sanjay
    • Geomechanics and Engineering
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    • v.13 no.6
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    • pp.963-975
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    • 2017
  • Improvement of soft clay deposit by preloading with vertical drains is one of the most popular techniques followed worldwide. These drains accelerate the rate of consolidation by shortening the drainage path. Although the analytical and numerical solutions available are mostly based on equal strain hypothesis, the adoption of free strain analysis is more realistic because of the flexible nature of the imposed surcharge loading, especially for the embankment loading used for transport infrastructure. In this paper, a numerical model has been developed based on free strain hypothesis for understanding the behaviour of soft ground improvement by vertical drain with preloading. The unit cell analogy is used and the effect of smear has been incorporated. The model has been validated by comparing with available field test results and thereafter, a hypothetical case study is done using the available field data for soft clay deposit existing in the eastern part of Australia and important conclusions are drawn therefrom.

Evaluation of Bearing Capacity and Load Transfer Characteristics of Point Foundation(PF) Method through the Large Plate Bearing Test (대형 평판재하시험을 통한 PF 공법의 하중전이 특성 분석)

  • Kang, Min-Su;Jo, Myung-Su;Koh, Yong-Taek
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.142-143
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    • 2021
  • The general ground conditions in Korea are distributed in order of fill, deposit soil, weathered soil, weathered rock, soft rock. The fill soil and deposit soil located at the top have relatively low strength compared to the lower layer, and they are sometimes classified as soft ground according to the standard penetration test results. In this study, the PF method, a ground improvement method, was applied to the soft layer, a large plate load test was conducted on the improved ground, and the results were reviewed.

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Numerical modelling of Haarajoki test embankment on soft clays with and without PVDs

  • Yildiz, Abdulazim;Uysal, Firdevs
    • Geomechanics and Engineering
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    • v.8 no.5
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    • pp.707-726
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    • 2015
  • This paper investigates the time dependent behaviour of Haarajoki test embankment on soft structured clay deposit. Half of the embankment is constructed on an area improved with prefabricated vertical drains, while the other half is constructed on the natural deposit without any ground improvement. To analyse the PVD-improved subsoil, axisymmetric vertical drains were converted into equivalent plane strain conditions using three different approaches. The construction and consolidation of the embankment are analysed with the finite element method using a recently developed anisotropic model for time-dependent behaviour of soft clays. The constitutive model, namely ACM-S accounts for combined effects of plastic anisotropy, interparticle bonding and degradation of bonds and creep. For comparison, the problem is also analysed with isotropic Soft Soil Creep and Modified Cam Clay models. The results of the numerical analyses are compared with the field measurements. The results show that neglecting effects of anisotropy, destructuration and creep may lead to inaccurate predictions of soft clay response. Additionally, the numerical results show that the matching methods accurately predict the consolidation behaviour of the embankment on PVD improved soft clays and provide a useful tool for engineering practice.

Azisymmetric Nonlinear Consolidation Analysis for Drainage-Installed Compressible Deposits (배수재가 설치된 압축성 지반의 축대칭 비선형 압밀해석)

  • 김윤태;이승래
    • Geotechnical Engineering
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    • v.12 no.1
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    • pp.5-20
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    • 1996
  • In order to accelerate the rate of consolidation settlement and to gain a required shear strength for a given soft clay deposit, the preloading technique combined with a vertical drainage system has been widely applied. In this'study, the theory of axisymmetric consolidation which considers the variation of compressibility and permeability during the conslidation process, has ben developed. A computer program named AXICON for the analysis of axisymmetric nonlinear consolidation is developed by adopting an explicit finite difference method. Smear and well resistance effects are also considered. The AXICON is capable of analyzing the consolidation behavior of multi -layered deposits and simulates time dependent loading sequence. The results of AXICON are validated with analytical solutions of Hansbo and Barron, and compared with insitu settlements and pore pressures measured in a soft clay deposit.

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A Study on a Compression Index for Settlement Analysis of SCP Treated Ground Using Back Analysis (역해석을 이용한 모래다짐말뚝(SCP)으로 개량된 연약점토지반의 압축지수 결정에 관한 연구)

  • Hwang, Sungpil;Im, Jongchul;Kwon, Jeonggeun;Kang, Yeounike;Joo, Ingon
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.7
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    • pp.5-14
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    • 2010
  • The paper processed settlement analysis using Finite Elements Method(FEM). Because Stress Distribution Ratio has to be decreased, for settlement analysis of soft clay deposit improved by sand compaction piles(SCP). Back analysis was processed comparing the measured settlements of laboratory model tests and finite element analysis where the SCP treated area was assumed as mixed ground with clay deposit rather than being a composite ground. The paper proposes a methodology which employs a compression index($C_c$) for settlement analysis of soft clay deposit improved by sand compaction piles from the back analysis. This approach is applied to a field measurement case(A revetment founded on the SCP improved clay deposit with the replacement ratio of 45%).

Quick Surface Strengthening of Soft Dredged Clay Fill by Dividing the Layer into Self Consolidation and Desiccation (점성토 준설매립지반의 자중압밀과 대기건조 영역분리에 의한 표층고결 촉진공법)

  • Kim, Hyun-Tae;Kim, Seung-Wook;Kim, Sang-Kyu
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.499-506
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    • 2004
  • The use of dredged soft marine clay is increasing due to a shortage of coarse material available. This paper presents a stabilization method that can increase shear strength of the surface layer of a dredged clay deposit at dates much earlier than usual. The desiccation of the upper soft 1-2m layer can be accelerated by interrupting water seeping from its bottom with impervious geotextile. Just below the geotextile, enough pervious material is provided so that the underlying deposit can be drained through it. This scheme is proved to be effective through theoretical analysis.

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Study on CGP-Anchor of Open-Cuts in Abandoned Coal Fill Deposit (폐탄매립층의 흙막이공사에서 CGP-앵커 시공사례연구)

  • 천병식;양형칠
    • Proceedings of the KSR Conference
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    • 2001.05a
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    • pp.416-423
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    • 2001
  • The object of this study is to determine the application of friction and ground stress type CGP(Compaction Grouting Pack)-anchor in retaining wall construction on the soft ground by executing in the fill deposit with abandoned coal. In this study the effect of CGP-anchors as retaining wall anchor on the soft ground anchor was evaluated through measuring displacement according to tensile strength by acting tensile strength after equipping CGP-anchors. From the field tests results, CGP-anchor was determined to be considerably effective as retaining wall anchor on the soft ground by showing that the maximum displacement was 60mm and the elastic displacement was within 50mm by 53ton tensile strength.

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