• Title/Summary/Keyword: 타설경계면

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Analysis of Diameter Effects on Skin Friction of Drilled Shafts in Sand (사질토 지반에 설치된 현장타설말뚝의 말뚝지름에 따른 주면마찰력 분석)

  • Lee, Sung-June
    • Journal of the Korean Geotechnical Society
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    • v.29 no.1
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    • pp.161-170
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    • 2013
  • In this paper, numerical pile segment analysis is conducted with an advanced soil elastoplastic model to investigate the diameter effects on skin friction behaviour of a drilled shaft in sand. Ultimate skin friction and 't-z' behavior from the pile segment analyses for drilled shafts show good agreement with those from design methods. Higher ultimate skin friction for the smaller diameter pile is related to the greater increase in the effective radial stress at the interface due to the localized dilation at and near the pile interface. Stiffer t-z curve for the smaller diameter pile is related to the early occurrence of three shear stages (early, dilation, constant volume shear stages). The diameter effects on ultimate skin friction of drilled shafts are more prominent for denser sand and lower confining pressure.

A Study on the Deformation Behavior of Nonwoven Geotextiles Reinforced Soil Walls Based on Literature Reviews (문헌조사에 근거한 부직포 보강토옹벽의 거동에 관한 연구)

  • Won, Myoung-Soo;Kim, Tae-Wan;Roh, Jae-Kune;Kim, Hyoung-Wan
    • Journal of the Korean Geosynthetics Society
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    • v.9 no.1
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    • pp.21-30
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    • 2010
  • To understand the deformation behavior of nonwoven geotextiles(NWGT) reinforced soil wall, analyses of load-elongation properties, soil-reinforcement interface friction, laboratory model tests, and field cases throughout literature reviews are being studied in this paper. According to the analyses results, the stiffness and tensile strength of NWGT is increased in proportion to confinement pressures, and the interface shear strength at soil-NWGT appeared to be stronger than soil-geogrid interface. The deformation at the beginning of loading on NWGT reinforced soil wall is larger than geogrid reinforced soil wall, but the wall deformation with NWGT is smaller than the wall of geogrid after passing some loading point in laboratory model tests. Case analysis results have shown that the facing of NWGT reinforced soil wall should be rigid enough to be used as a permanent wall, and NWGT and in-situ poor soil can be used for reinforcement and backfill respectively if the wall is constructed as pre-reinforced soil body and with post-facing that has a full-height rigid concrete.

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Evaluation of Load Transfer Characteristics of Barrette Pile Based on Bi-directional Loading Tests (양방향 재하시험결과를 활용한 바렛말뚝의 하중전이특성 평가)

  • Park, Seong Wan;Lim, Dae Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.2C
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    • pp.41-49
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    • 2009
  • Due to the increased size of civil infrastructure and the cost of materials, the needs exists for utilizing large sized cast-inplace piles in lieu of conventional precast piles. Among them, the barrette pile has become more commonly used in fields where a diaphragm wall is the retaining wall, to improve workability and economical efficiency, and to ensure hole stability under deep soil layers. In this paper, the bearing capacity and displacement characteristics of the barrette pile are evaluated by using the bi-directional loading test data obtained from four different sites. In addition, the design value of pile shaft resistance, ${\beta}$, is assessed with previous literatures and load transfer analysis. Finally, numerical analyses were performed to analyze the load-displacement behavior, and the interface effect on the piles, using the 3-dimensional finite element method.

Comparison of Flexural Tensile Behaviors with Different Filling Directions in Producing UHPCC Flexural Member (UHPCC 휨부재 제작 시 타설 중 충전방향에 따른 휨인장거동의 변화)

  • Kang, Su-Tae;Ryu, Gum Sung;Koh, Kyung Taek;Kim, Sunyong
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.2
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    • pp.447-455
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    • 2014
  • This study was intended to estimate the efficiency of inducing fiber arrangement in UHPCC (Ultra High Performance Cementitious Composites). For the purpose, UHPCC members produced by several different placing methods according to flow characteristics were prepared; flexural behaviors were compared and correlation between the flexural behavior and the characteristics of fiber arrangement was investigated. Test results showed that placing method for inducing specific fiber arrangement had a considerable influence on the flexural performance. The standard specimen in which fibers are induced to be directed parallel to the principle tensile direction presented higher flexural tensile strength but lower variation. Therefore it should be considered that the flexural tensile strength actually developed in UHPCC member may be highly different and in lager variation. The qualitative variation of fiber arrangement according to the flow of UHPCC was also predicted considering the flow pattern and the boundary effect; the prediction provided good explanation to the difference in the flexural behavior according to the induced flow.

FE Analysis of Rock-Socketed Drilled Shafts Using Load Transfer Method (유한요소해석을 통한 암반에 근입된 현장타설말뚝의 하중전이거동 분석)

  • Seol, Hoon-Il;Jeong, Sang-Seom;Kim, Young-Ho
    • Journal of the Korean Geotechnical Society
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    • v.24 no.12
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    • pp.33-40
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    • 2008
  • The load distribution and deformation of rock-socketed drilled shafts subjected to axial loads are evaluated by a load-transfer method. The emphasis is on quantifying the effect of coupled soil resistance in rock-socketed drilled shafts using the 2D elasto-plastic finite element analysis. Slippage and shear load transfer behavior at the pile-soil interface are investigated by using a user-subroutine interface model (FRlC). It is shown that the coupled soil resistance provides the influence of pile toe settlement as the shaft resistance is increased to an ultimate limit state. The results show that the coupling effect is closely related to the value of pile diameter over rock mass modulus (D/$E_{mass}$) and the ratio of total shaft resistance against total applied load ($R_s$/Q). Through comparisons with field case studies, the 2D numerical analysis reseanably presented load transfer of pile and coupling effect due to the transfer of shaft shear loading, and thus represents a significant improvement in the prediction of load deflections of drilled shafts.

Deformation Analysis of Soft Foundation with Vertical Drain Wells using the Interface Element Method -With Emphasis on Model Foundation and Actual Sand Drain Well Foundation- (접합요소에 의한 Vertical Drain Well 지반의 변형해석 - 모델지반과 실제 Sand Drain Well 지반을 중심으로 -)

  • Lee, Jean Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.4
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    • pp.227-237
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    • 1993
  • This paper dealt with numerical analysis of sand drain considering the smear effect around drain wells and discontinuous deformation behavior due to difference in rigidity between drain materials and adjacent clayey soils. Biot's equation was selected as governing equation coupled with MODCAM (Modified Cam-clay) model or EVP(Elasto-Viscoplastic) model as constitutive equation. The validity as well as the accuracy of the method developed by author was checked by comparing the proposed method with those by Siriwardane and Ghaboussi using joint element. The FEM analysis developed in this study was applied to both 2-dimensional model foundation and actual foundation. the result of which proved to be satisfactory.

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Evaluation on Structural Safety for Bearing seat according to Replacement of Bridge Bearing (교량받침 교체에 따른 보자리 구조 안전성 평가)

  • Choi, Jung-Youl;Lee, Hee-Kwang;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.4
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    • pp.753-760
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    • 2020
  • In this study, the structural safety of the bearing support was analysed by applying the vertical load (bearing design load) and horizontal load (horizontal force generated during an earthquake) using a precise three-dimensional numerical model. The results of stress and displacement of newly-poured concrete and welded rebars were confirmed numerically. Numerical results show that the increase in the horizontal force and the height of the beam causes the concrete cracking and the stress increase of the rebar connections due to the increase of the stress at the new concrete interface. Therefore, it was analyzed that the increase in the height of bearing support is directly related to the horizontal force and it is necessary to apply the bearing support height appropriate for the bearing support capacity. It was proposed that a method of setting the height of the bearing support suitable for the bearing capacity and determining the reinforcement by presenting the guideline with the correlation between the horizontal force acting on the bearing support and its height.

A Program Development for Prediction of Negative Skin Friction on Piles by Consolidation Settlement (압밀침하를 고려한 말뚝의 부마찰력 예측 프로그램 개발)

  • Kim, Hyeong-Joo;Mission, Jose Leo C.
    • Journal of the Korean Geotechnical Society
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    • v.25 no.9
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    • pp.5-17
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    • 2009
  • The microcomputer program PileNSF (Pile Negative Skin Friction) is developed by the authors in a graphical user interface (GUI) environment using $MATLAB^{(R)}$ for predicting the bearing capacity of a pile embedded in a consolidating ground by surcharge loading. The proposed method extends the one-dimensional soil-pile model based on the nonlinear load transfer method in OpenSees to perform an advanced one-dimensional consolidation settlement analysis based on finite strain. The developed program has significant features of incorporating Mikasa's finite strain consolidation theory that accounts for reduction in the thickness of the clay layer as well as the change of the soil-pile interface length during the progress of consolidation. In addition, the consolidating situation of the ground by surcharge filling after the time of pile installation can also be considered in the analysis. The program analysis by the presented method has been verified and validated with several case studies of long-term test on single piles subjected to negative skin friction. Predicted results of negative skin friction (downdrag and dragload) as a result of long from consolidation settlement are shown to be in good agreement with measured and observed case data.

Evaluation of the Pull-out Resistance of the SMA Wire Connector (SMA 와이어를 이용한 연결재의 인발저항성능 평가)

  • Jung, Chi-Young;Woo, Tae-Ryeon;Lee, Jong-Han;Cheung, Jin-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.1
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    • pp.130-137
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    • 2019
  • Precast concrete (PC) structure is one of the type of the structures which is made in a facility prior to installing it to a construction field. The contact surfaces between two PC structures should be treated for obtaining enough binding force by inducing prestressing force. However, in the many cases, the contact surface causes the crack and leakage of water. These cracks and water leakage can cause the corrosion of the rebar, and the corrosion of the rebar can severely reduce the long-term durability. In this study, the SMA wire connector is suggested to solve the problem with the contact surfaces between two PC structures. The pull-out resistance of the suggested SMA wire connector is evaluated by conducting the tests to find the effect of the number of wires, shape of connector part, and shape memory effect. As a result of this study, the empirical formula is suggested to estimate the pull-out resistance related with the effects of the shape of the connector, shape memory effect, and the adhesive force. The validity between the estimated pull-out resistance and the measured value is confirmed.