• Title/Summary/Keyword: soil bearing capacity

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Experiment on the Effective Helix Area to Determine the Bearing Capacity of Helical Steel Piles (나선형 강관파일의 날개 유효면적 산정을 위한 지지력 실험)

  • Lee, Min-Joo;Kim, Kyoung-Min;Rhim, Hong-Chul;Seo, Gum-Bae
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2010.05a
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    • pp.25-27
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    • 2010
  • Helical steel piles are being widely used in foundation for the buildings in urban areas because of their high compressive and tensile capacities. Helical steel piles have many advantages; ease installation, a vibration-free and low level of noise process, and so on. However, the most researches are about the capacity of helical steel piles under uplift condition. Therefore, this paper focuses on the capacity under compressive loading according to the soil condition. The bearing capacity of helical steel piles varies with the diameter of the helix and shaft and the bearing area of helical steel piles is not always identical with the sum of helix and shaft area due to the difference of each bearing mechanism. Therefore, the experiment with the parameters of the ratio of helix and shaft diameter and soil condition will be carried out to survey the effective helix area under a given soil condition for the bearing capacity of helical steel piles.

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Square footing on geocell reinforced cohesionless soils

  • Biswas, Sefali;Mittal, Satyendra
    • Geomechanics and Engineering
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    • v.13 no.4
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    • pp.641-651
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    • 2017
  • Ground improvement with use of geosynthetic products is globally accepted now. The present paper discusses the improvement in bearing capacity of square footing placed at surface of cohesionless soil reinforced with geocell. Mohr-Coulomb failure criterion has been used in the observations. To study effects of geocell with respect to planar geogrid, model tests were conducted on planar reinforcement also. A comparative study of unreinforced soil and soil reinforced with plane geogrid and geocell has also been made. Numerical analysis results obtained by PLaxis have been compared with those obtained from model tests and were found to be in good agreement. A parametric study revealed the role of length of reinforcement, spacing between layers, placement of reinforcement from top surface etc. on bearing capacity. A design example given in paper illustrates the savings in cost of construction of footing on reinforced sand. The study shows that there is improvement in bearing capacity with respect to unreinforced soil which is of the order of 86%. Similarly settlement reduction is 13.07% for single layer of geocell which for double layers of geocell is 693% and 86.48% respectively. The cost reduction in case of reinforced soil is 35% as compared to unreinforced soil.

Experimental estimate of Nγ values and corresponding settlements for square footings on finite layer of sand

  • Dixit, Manish S.;Patil, Kailas A.
    • Geomechanics and Engineering
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    • v.5 no.4
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    • pp.363-377
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    • 2013
  • Any structure constructed on the earth is supported by the underlying soil. Foundation is an interfacing element between superstructure and the underlying soil that transmits the loads supported by the foundation including its self weight. Foundation design requires evaluation of safe bearing capacity along with both immediate and long term settlements. Weak and compressible soils are subjected to problems related to bearing capacity and settlement. The conventional method of design of footing requires sufficient safety against failure and the settlement must be kept within the allowable limit. These requirements are dependent on the bearing capacity of soil. Thus, the estimation of load carrying capacity of footing is the most important step in the design of foundation. A number of theoretical approaches, in-situ tests and laboratory model tests are available to find out the bearing capacity of footings. The reliability of any theory can be demonstrated by comparing it with the experimental results. Results from laboratory model tests on square footings resting on sand are presented in this paper. The variation of bearing capacity of sand below a model plate footing of square shape with variation in size, depth and the effect of permissible settlement are evaluated. A steel tank of size $900mm{\times}1200mm{\times}1000mm$ is used for conducting model tests. Bearing capacity factor $N_{\gamma}$ is evaluated and is compared with Terzaghi, Meyerhof, Hansen and Vesic's $N_{\gamma}$ values. From the experimental investigations it is found that, as the depth of sand cushion below the footing ($D_{sc}$) increases, ultimate bearing capacity and settlement values show an increasing trend up to a certain depth of sand cushion.

ANALYSIS AND DESIGN OF MAT FOUNDATION FOR HIGH-RISE BUILDINGS (초고층 건물의 전면기초(MAT기초) 해석 및 설계)

  • Hong, Won-Gi;Hwang, Dae-Jin;Gwon, Jang-Hyeok
    • Proceedings of the Korean Geotechical Society Conference
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    • 1994.09a
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    • pp.94-110
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    • 1994
  • Types of foundation of high rise buildings are primarily determined by loads transmitted from super structure, soil bearing capacity and available construction technology. The usd of deep foundation cannot be justified due to the fact that rock of enough bearing capacity is not found down until 90 ~ 100m. When a concentration of high soil pressure must be distributed over the entire building area, when small soft soil areas must be bridged, and when compressible strata are located at a shallow depth, mat foundation may be useful in order to have settlement and differential settlement of variable soils be minimized. The concept of mat foundation will also demonstrate some difficulities of applications if the load bearing demand directly carried down to the load -bearing strata exceeds the load -bearing capacity. This paper introduces both the analysis and design of mat type foundation for high rise buildings as well as the methodology of modelling of the soil foundation, especially, engineered to redistribute the stress exceeding the soil bearing capadity. This process will result in the wid spread of stresses over the entire building foundation.

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Estimation on Bearing Capacity of Environmentally Sustainable Geotextile Gabion Using Oystershell (굴패각을 이용한 친환경적 지오텍스타일 게비언의 지지력 평가)

  • Shin, Eun-Chul;Park, Jeong-Jun
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.10 no.6
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    • pp.44-52
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    • 2007
  • Recently, oystershell wastes cause serious environmental problem and the need for the researches on the recycling of oystershell have been increased and various methods are already in operation. Field plate bearing tests and numerical analysis were performed to investigate the bearing capacity of oystershell filled geotextile gabion which utilized the waste oystershell at the coastal oyster farm site. The waste oystershell mixed soil specimens were prepared for the laboratory test and field test in terms of varying blending ratio of granite soil and oystershell. Based on the cyclic plate load test results, the spring constant, subgrade modulus of ground, and the reinforcing parameters were determined. The field plate load test results indicate that the bearing capacity of the soil ground with the oystershell mixed ratio of 20% is greater than that of the original ground. Two-dimensional numerical analysis was evaluated the expected deformation in the given conditions. Analysis results show a similar characteristics on bearing capacity with the results of the field plate load test. These findings suggest that the oystershells are very promising construction materials for landfill and earth embankment in coastal area.

A Study on Characteristics of Strength Increase and Bearing Capacity in Dredged and Reclaimed Soil due to Desiccation Shrinkage (준설토의 건조수축에 의한 강도증가 특성과 지지력에 관한 연구)

  • Yoo, Nam-Jae;Lee, Jong-Ho;Lee, Myung-Woog;Kim, Hyun-Joo
    • Journal of Industrial Technology
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    • v.20 no.A
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    • pp.101-111
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    • 2000
  • This research is results of experimental and numerical works on characteristic of strength increase and bearing capacity in dredged and reclaimed soil due to desiccation shrinkage. For a soil sampled from southern coastal area in Korea, basic soil property tests and standard consolidation test with falling head permeability tests were carried out to obtain consolidational characteristics of soil. Double cone penetration test, laboratory vane test and unconfined compression test were also performed to investigate the change of shear strength with degree of desiccation. Model tests were performed in 1G environment and 30G level artificially accelerated condition by using the centrifuge model test facilities to investigate the bearing capacity of desiccated ground. Test results were analyzed by using the theoretical and load-settlement characteristics method proposed by Meyehof & Hanna(1978). On the other hands, the numerical technique, using the finite strain consolidation theory considering the effect of desiccation was used to estimate the appropriate time of using heavy construction equipments in field with respect to strength increase due to desiccation.

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Evaluation of Bearing Capacity of Multi-layered Soil Deposits (개별요소법에 의한 다층지반의 지지력 산정)

  • Park Jun;Jee Sung-Hyun;Lee Seung-Rae;Park Hyun-Il
    • Journal of the Korean Geotechnical Society
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    • v.22 no.6
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    • pp.63-69
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    • 2006
  • In this paper, a method is presented for estimating the bearing capacity of shallow foundations based on the Discrete Element Method (DEM). By applying Winkler-springs for accounting for the compatibility between soil blocks, the proposed method can estimate the state of stress at failure surface and the ultimate bearing capacity. For the investigation of the application of the method, example problems about shallow foundations on the single layer and two layers soil are analyzed.

The study on the Characteristics of Ultimate Bearing Capacity and Major Design Parameters for Single Stone Column (단일 쇄석다짐말뚝의 지지력 특성과 주요 설계 파라미터에 관한 고찰)

  • Chun, Byung-Sik;Kim, Won-Cheul;Jo, Yang-Woon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.552-560
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    • 2004
  • Stone column is a soil improvement method and can be applicable for loose sand or weak cohesive soil. Since the lack of sand in Korea, stone column seems one of the most adaptable approach for poor ground as a soil improvement method. However, this method was not studied for practical application. In this paper, the most effective design parameters for the being capacity of stone column were studied. The parametric study of major design factors for single stone column was carried out under the bulging and general shear failure condition, respectively. Especially, a test result of single stone column by static load was compared with the bearing capacity values of suggested formulas. The analysis result showed that the ultimate bearing capacity by the formula was much less than the measured value by the static load test. Especially, the result of the parametric study under general shear failure condition showed that the bearing capacity has apparent difference between each suggested formulas with the variation of the major design parameters. Therefore, the result of this study can be a suggestion which is applicable for the field test and the future research.

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Bearing capacity of strip footings on unsaturated soils under combined loading using LEM

  • Afsharpour, Siavash;Payan, Meghdad;Chenari, Reza Jamshidi;Ahmadi, Hadi;Fathipour, Hessam
    • Geomechanics and Engineering
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    • v.31 no.2
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    • pp.223-235
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    • 2022
  • Bearing capacity of shallow foundations is often determined for either dry or saturated soils. In some occasions, foundations may be subjected to external loading which is inclined and/or eccentric. In this study, the ultimate bearing capacity of shallow foundations resting on partially saturated coarse-grained cohesionless and fine-grained cohesive soils subjected to a wide range of combined vertical (V) - horizontal (H) - moment (M) loadings is rigorously evaluated using the well-established limit equilibrium method. The unified effective stress approach as well as the suction stress concept is effectively adopted so as to simulate the behaviour of the underlying unsaturated soil medium. In order to obtain the bearing capacity, four equilibrium equations are solved by adopting Coulomb failure mechanism and Bishop effective stress concept and also considering a linear variation of the induced matric suction beneath the foundation. The general failure loci of the shallow foundations resting on unsaturated soils at different hydraulic conditions are presented in V - H - M spaces. The results indicate that the matric suction has a marked influence on the bearing capacity of shallow foundations. In addition, the effect of induced suction on the ultimate bearing capacity of obliquely-loaded foundations is more pronounced than that of the eccentrically-loaded footings.

Bearing Capacity of Model Open -Ended Steel Pipe Pile Driven into Sand Deposit (모래지반에 타입된 모형 개단강관 말뚝의 지지력 분석)

  • Baek, Gyu-Ho;Lee, Jong-Seop;Lee, Seung-Rae
    • Geotechnical Engineering
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    • v.9 no.1
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    • pp.31-44
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    • 1993
  • Model tests in calibration chamber with open -ended steel pipe pile have been performed in sand deposit to clarify effect of soil plug on bearing capacity, load transfer mechanisms in soil plug, and behavior of soil plug under dynamic and static conditions. Model piles were devised so that bearing capacity of open -ended pile could be measured separately into outside skin friction, inside skin friction due to soil plug -pile interaction and end bearing force on the section of steel pipe pile. It may be concluded, form the test results, that the plugging level of open -ended pile is more correctily defined by specific recovery ratio, y, rather than by plug length ratio, PLR, and the major part of inside skin friction is generated within the range of three times as long as the inner diameter of the pile from the pile tip. The ratio of inside skin friction to total bearing capacity is much larger than that of outside skin friction to total bearing capacity. Therefore, the bearing capacity of pile could not be well predicted, unless the inside skin friction is properly taken into account.

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