• Title, Summary, Keyword: Embedment ratio

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Effect of Embedment Ratio and Loading Rate on Uplift Adhesion Factor of Concrete Driven Pile (근입비와 인발속도가 콘크리트 항타말뚝의 인발부착계수에 미치는 영향)

  • Kim Jong-In;Park Jeong-Jun;Shin Eun-Chul
    • Journal of the Korean Society for Railway
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    • v.8 no.4
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    • pp.367-371
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    • 2005
  • Pile foundations are utilized when soil is so weak that shallow foundations are not suitable or point load is concentrated in small area. Such soil can be formed by the land reclamation works which have extensively been executed along the coastal line of southern and western parts of the Korean Peninsula. The working load at pile is sometimes subjected to not only compression load but also lateral load sad uplift forces. But in most of the practice design, uplift capacity of pile foundation is not considered and estimation of uplift capacity is presumed on the compression skin friction. This study was carried out to determine that the effect of embedment ratio and loading rate on uplift adhesion factor of concrete pile driven in clay. Based on the test results, the critical embedment ratio is about 9. Adhesion factor is constant under the critical embedment ratio, and decreasing over the critical embedment ratio. Also, adhesion factor is increased with the loading rate is increased.

Effect of Embedment Depth of Footing on Behavior of Compensated Foundation (기초의 근입깊이가 보상기초의 거동에 미치는 영향)

  • Lee, Seung-Hyun;Han, Jin-Tae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.2
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    • pp.1477-1482
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    • 2015
  • In order to find out the effect of embedment ratio on behavior compensated foundation, numerical analyses were performed. Bearing capacity ratios obtained from numerical analyses were greater than those obtained from theoretical equations and it could be seen that the bearing capacity ratio was proportional to the embedment ratio with only exception of the case of square footing in which bearing capacity ratio was increased rapidly with the embedment ratio. For the case of strip footing on sand, the bearing capacity ratios obtained from the numerical analyses and Meyerhof equation were similar with each other and magnitudes of those were as much as square of the embedment ratio but the bearing capacity ratios were little affected by the embedment ratios for the case of strip footing on clay. It can be said that the bearing capacity ratios obtained from the square footing are greater than those obtained from the strip footing. According to the numerical analysis, values of settlement ratios which correspond to the embedment ratio of one were about 0.4 and settlement ratios were decreased with increase of the embedment ratios. Settlement ratios of the loose sand were smaller than those of the dense sand and the clay.

Evaluation of Plugging Effect of Open-Ended Model Pipe Pile (개단 강관말뚝의 폐색효과에 대한 모형실험 연구)

  • Kim, Myoung Mo
    • Journal of The Korean Society of Civil Engineers
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    • v.7 no.3
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    • pp.175-181
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    • 1987
  • Plugging effect of open-ended pipe piles is known to have a close relationship with the ratio of an embedment depth to a pile diameter, i.e., the relative embedment ratio. To evaluate this relationship in the concrete, load tests are performed on the open and the close ended model piles varying the relative embedment ratio as well as the relative density of the model test ground. Cross-shaped hollow plates are attached at the open pile ends to reduce the effective pile diameters, on which load tests are also performed. As a result, it is confirmed that higher plugging effect may be obtained in the denser ground at lower relative embedment. However, 100% plugging effect can be obtained at the relative embedment ratio of 25 or bigger regardless of the density of the ground. Increment of the plugging effect by introducing the cross-shaped attachment can hardly be achieved.

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Influence of Suction Force of Plate Anchor Embedded in Kaolinite (Kaolinite에 근입된 앵커에서 흡입력이 미치는 영향)

  • 이준대;이봉직
    • Journal of the Korean Society of Safety
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    • v.12 no.4
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    • pp.108-113
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    • 1997
  • Plate anchors are primarily used in the foundation construction of earth-supported and earth-retaining structures. In order to estimate uplift capacity as well as suction force of clay, model tests were peformed with respect to various embedment depths and two different moisture contents in the prepared saturated kaolinite. Further, suction effects on the ultimate uplift capacity, at the various embedment depths of anchor, were also taken into account. Test results show that ultimate uplift capacity including suction force increases from 4.2kg at H/D=1 upto 11.6kg at H/D=5 in K1 and from 2.3kg at H/D=1 upto 7.3kg at H/D=5 in K2 respectively. The ratio of $F_s/Q_n/$ decreases along with the increases in the embedment ratio. In general, mud suction force under the ultimate uplift capacity in kaolinite decreases or becomes constant along with the increase of the embedment ratio.

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Nonlinear soil parameter effects on dynamic embedment of offshore pipeline on soft clay

  • Yu, Su Young;Choi, Han Suk;Lee, Seung Keon;Park, Kyu-Sik;Kim, Do Kyun
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.7 no.2
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    • pp.227-243
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    • 2015
  • In this paper, the effects of nonlinear soft clay on dynamic embedment of offshore pipeline were investigated. Seabed embedment by pipe-soil interactions has impacts on the structural boundary conditions for various subsea structures such as pipeline, riser, pile, and many other systems. A number of studies have been performed to estimate real soil behavior, but their estimation of seabed embedment has not been fully identified and there are still many uncertainties. In this regards, comparison of embedment between field survey and existing empirical models has been performed to identify uncertainties and investigate the effect of nonlinear soil parameter on dynamic embedment. From the comparison, it is found that the dynamic embedment with installation effects based on nonlinear soil model have an influence on seabed embedment. Therefore, the pipe embedment under dynamic condition by nonlinear parameters of soil models was investigated by Dynamic Embedment Factor (DEF) concept, which is defined as the ratio of the dynamic and static embedment of pipeline, in order to overcome the gap between field embedment and currently used empirical and numerical formula. Although DEF through various researches is suggested, its range is too wide and it does not consider dynamic laying effect. It is difficult to find critical parameters that are affecting to the embedment result. Therefore, the study on dynamic embedment factor by soft clay parameters of nonlinear soil model was conducted and the sensitivity analyses about parameters of nonlinear soil model were performed as well. The tendency on dynamic embedment factor was found by conducting numerical analyses using OrcaFlex software. It is found that DEF was influenced by shear strength gradient than other factors. The obtained results will be useful to understand the pipe embedment on soft clay seabed for applying offshore pipeline designs such as on-bottom stability and free span analyses.

Pullout Test of Headed Reinforcement 2: Deep Embedment

  • Choi, Dong Uk;Shin, InYong
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.1091-1096
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    • 2003
  • Pullout tests of single headed bars using plain concrete blocks indicate that the embedment depth of $10d_b$ is in general required for the headed bars to develop pullout strength equivalent to 125% of bar yield strength. In this experimental study, test results of multiple headed bars installed in reinforced concrete column sections are presented. Test variables included embedment depth, column main reinforcement ratio, and spacing of column ties. 2D29 bars were pulled out at one time from normal strength concrete. Test results indicated that the embedment depths, column tie spacings, and column main reinforcement ratios all influenced the pullout strengths of the headed bars. When the embedment depth was not sufficient, narrow tie spacings especially resulted in increased pullout strengths of the headed bars. Test results also indicated that the embedment depth of 15㏈ was sufficient for the closely spaced two headed bars (head-to-head spacing =$6d_b$) to develop pullout strength equivalent to 125% of the bar yield strength.

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An Experimental Study on Suction Force of Plate Anchor Embedded in Bentonite (벤토나이트에 근입된 앵커의 흡입력에 관한 실험적 연구)

  • 이준대
    • Journal of the Korean Society of Safety
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    • v.16 no.2
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    • pp.97-102
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    • 2001
  • Anchors are often used in construction of foundations such as transmission towers to resist uplifting forces. When plate anchors are embedded in soft clay, they may undergo a deformation under the pressure of sustained load. In soft saturated clays, the suction force can be a large par of the ultimate uplift capacity. This study is to present recent laboratory model test results conducted to evaluate the nature of variation of the suction force for plate anchors with shear strength and embedment ratio. The ratio of F$_{s}$Q$_{n}$ versus H/D in bentonite decreases with the increase of the embedment ratio.o.o.

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Bearing of Strip Foundation on Geogrid-Reinforced Sand With Embedment Depth (기초의 근입깊이를 고려한 지오그리드 보강 사질토지반의 지지력 평가)

  • 신은철;신동훈;오영인
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.233-240
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    • 1999
  • The laboratory tests on geogrid-reinforced sand were conducted with considering embedment effect. The relative densities of sand are 60% and 80%, respectively. The embedment depths of foundation were varied as D$\_$f/B=0, 0.5, 1.0. Based on the model test results, (u/B)$\_$cr/, BCR$\_$u/, and (b/B)$\_$cr/, were determined. The optimum depth of reinforcement was determined. The embedment depth of foundation is greatly contributed on the bearing capacity of geogrid-reinforced sand.

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Pullout Characteristics of Multi Helical Anchors in Clay (점성토 지반에서의 다중 헬리컬 앵커의 인발 특성)

  • 이준대;이봉직;이종규
    • Journal of the Korean Society of Safety
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    • v.12 no.4
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    • pp.114-121
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    • 1997
  • Helical anchors are foundation structure that designed to resist uplift loads are installed by applying in load to shaft while rotating it into the ground. These can be a cost effective means of proving tension anchorage for foundation where soil conditions permit their installation because of ease of installation. At present time, tapered helical anchors are commonly used to carry uplift loads. The uplift capacity includes the following factors : the height of overburden above the top helix, the resistant along a cylinder, the weight of the soil in the cylinder and suction force. In order to make clear behavior characteristics of helical anchors with pullout, model tests were conducted with respect to various embedment depth, space of helix, shape of helix. Based on the experimental study, the following conclusions are drawn. 1) The uplift capacity of multi helical anchors increase with embedment ratio of anchors The increase is smooth after critical uplift capacity. 2) Critical breakout factors and critical embedment ratio of multi helical anchor exist 7∼8, 4∼6 respectively. 3) Variation of uplift capacity with helix spaces show down after S/D=5. 4) Critical breakout factors of helical anchor in the laboratory test are similar to Das's theory.

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Response of square anchor plates embedded in reinforced soft clay subjected to cyclic loading

  • Biradar, Jagdish;Banerjee, Subhadeep;Shankar, Ravi;Ghosh, Poulami;Mukherjee, Sibapriya;Fatahi, Behzad
    • Geomechanics and Engineering
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    • v.17 no.2
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    • pp.165-173
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    • 2019
  • Plate anchors are generally used for structures like transmission towers, mooring systems etc. where the uplift and lateral forces are expected to be predominant. The capacity of anchor plate can be increased by the use of geosynthetics without altering the size of plates. Numerical simulations have been carried out on three different sizes of square anchor plates. A single layer geosynthetic has been used as reinforcement in the analysis and placed at three different positions from the plate. The effects of various parameters like embedment ratio, position of reinforcement, width of reinforcement, frequency and loading amplitude on the pull out capacity have been presented in this study. The load-displacement behaviour of anchors for various embedment ratios with and without reinforcement has been also observed. The pull out load, corresponding to a displacement equal to each of the considered maximum amplitudes of a given frequency, has been expressed in terms of a dimensionless breakout factor. The pull out load for all anchors has been found to increase by more than 100% with embedment ratio varying from 1 to 6. Finally a semi empirical formulation for breakout factor for square anchors in reinforced soil has also been proposed by carrying out regression analysis on the data obtained from numerical simulations.