• Title/Summary/Keyword: End bearing capacity

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Study on the Evaluation of End Bearing Capacity of Pre-Bored Piles for the SPT-N value (SPT-N값에 따른 매입말뚝의 선단지지력 특성 연구)

  • Seo, Dong-Nam;Choi, Sang-Ho;Kim, Jin-Sik;Kim, Seong-Cheol;Lee, Dong-Hyeon;Cho, Seong-Jun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.11a
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    • pp.133-134
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    • 2020
  • The equation of end bearing capacity is applied differently depending on the type of pile, construction method, and load characteristics considering the construction standards. The bearing capacity equation of the design standard is presented in various ways according to the design conditions such as construction method and ground condition, etc. but, It does not reflect the ground strength according to the SPT-N value of weathered rock. This study analyzed the trend of allowable tip bearing capacity by pile diameter through about 480 dynamic loading tests conducted for the construction/quality management of piles for the last 6 years since 2015. The equation for the ultimate end bearing capacity per unit area according to the SPT-N value is presented. The proposed formula of ultimate end bearing capacity per unit area can be applied in the range of 15,000kN/m2 to 30,000kN/m2. The proposed formula, which complements the existing formula, enables pile design and construction/quality management.

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Experimental Study on the End Bearing Capacity of the Pile in a Group Pile (무리말뚝을 구성하는 개별말뚝의 선단지지력에 대한 실험연구)

  • Na, Yong Soo;Lee, Sang Duk
    • Journal of the Korean Geotechnical Society
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    • v.35 no.6
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    • pp.27-38
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    • 2019
  • Bearing capacity of a pile in homogeneous soil is the sum of end bearing and skin resistance, and the skin resistance is more prominent in sandy soil. Bearing capacity of a pile in pile groups especially in sandy ground should be designed under the consideration of the influence by the adjacent piles. In this study, the end bearing capacity of a pile in pile groups was experimentally investigated. For this purpose, piles were installed in sandy ground in a circular test box, and end bearing - settlement behavior of the pile was measured while the pile was loaded. As the results, end bearing - settlement relation curves of the piles showed a distinct limit value. Limit value of the end bearing was little affected by skin friction and pile diameter, and it became a constant value as pile penetrates deeper. End bearing was not affected by the adjacent piles in a group of piles, when their clearance was larger than the pile diameter.

Axial Load Transfer Behavior for Driven Open-ended End bearing Steel Pipe Pile (선단지지된 항타개단강관말뚝의 축하중전이거동)

  • 임태경;정성민;정창규;최용규
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.03a
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    • pp.589-596
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    • 2002
  • In this study, static pile load tests with load transfer measurement were accomplished in the field. Yield pile capacity (or ultimate pile capacity) determined by load-settlement-time relationship was determined and axial load transfer behavior was analyzed. In the test for the four test piles were behaved as end bearing pile but ratios of skin friction to total pile capacity were 27%∼33%.

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A Study on the Improvement of Bearing Capacity Prediction Equation for Auger-drilled Piling (매입말뚝공법의 지지력 예측식 개선에 관한 연구)

  • 최도웅;한병권;서영화;조성한
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.10a
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    • pp.382-389
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    • 2002
  • Recently, auger-drilled piling has been widely used in urban area to reduce the air pollution and noise. But this construction method that its basic theory was introduced from Japan may be changed depending on the each piling company and construction field condition. Therefore, the design code and management method for auger-drilled piling is not defined yet. Especially, the lack of research on the bearing capacity of auger-drilled piling leads to the absence of rational bearing capacity prediction equation. This paper presents the optimum design code and economical construction method of the auger-drilled piling by proposing the new bearing capacity prediction equation based on the site specific soil types and construction conditions. In this paper, existing bearing capacity prediction equations and current pile load tests were compared. And the end bearing capacity and skin friction characteristics were also analyzed by comparing the results of CAPWAP. From the results of analysis, a reliable bearing capacity prediction equation considered soil types is proposed.

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A Study on the Ultimate End Bearing Capacity of Drilled Shafts in Rocks (암반에 설치된 현장타설말뚝의 극한선단지지력에 관한 연구)

  • Jeong, Sangseom;Lee, Jaehwan;Kim, Dohyun
    • Journal of the Korean Geotechnical Society
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    • v.29 no.11
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    • pp.5-15
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    • 2013
  • The end bearing capacity of rock-socketed drilled shafts under axial loading is investigated by Hoek-cell tests and a numerical analysis. From the test results, it was found that the ultimate end bearing capacity ($q_{max}$) was influenced by pile diameter, rock mass modulus and the spacing of discontinuity. A new ultimate end bearing capacity method is proposed by taking end bearing capacity influence factors, including rock mass discontinuity, based on field data. Through comparisons with other field data, the proposed $q_{max}$ method represents a definite improvement in the prediction of ultimate end bearing capacity of rock-socketed drilled shafts.

Chord bearing capacity in long-span tubular trusses

  • Kozy, B.;Boyle, R.;Earls, C.J.
    • Steel and Composite Structures
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    • v.6 no.2
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    • pp.103-122
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    • 2006
  • The capacity of tubular truss chords subjected to concentrated reaction forces in the vicinity of the open end (i.e., the bearing region) is not directly treated by existing design specifications; although capacity equations are promulgated for related tubular joint configurations. The lack of direct treatment of bearing capacity in existing design specifications seems to represent an unsatisfactory situation given the fact that connections very often control the design of long-span tubular structures comprised of members with slender cross-sections. The case of the simple-span overhead highway sign truss is studied, in which the bearing reaction is applied near the chord end. The present research is aimed at assessing the validity of adapting existing specifications' capacity equations from related cases so as to be applicable in determining design capacity in tubular truss bearing regions. These modified capacity equations are subsequently used in comparisons with full-scale experimental results obtained from testing carried out at the University of Pittsburgh.

An Analysis on Co-relationships Between In-situ Investigation Methods and End Bearing Capacity of A Drilled Shaft Socketed into the Weathered Zone (풍화대소켓 현장타설말뚝의 극한단위선단지지력과 원위치 지반조사방법들과의 상관관계 분석)

  • Choi, Yongkyu;Kwon, Oh Sung;Lee, Jong Seong;Choi, Sung Soon;Jung, Sung Min
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2C
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    • pp.95-107
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    • 2010
  • To calculate the end bearing capacity of a drilled Shaft socketed into the rockmass, the unconfined compression strength could be used. But it is difficult to find the unconfined compression strength because it is impossible to get undisturbed samples in weathered soils and rocks. So, to calculate the end bearing capacity, the existing bearing formula could not be used. In this study, for five zones (near pile tip, tip~lower 1D, tip~lower 2D, upper 1D~lower 1D, upper 1D~lower 2D), the relationships between the characteristic values of in-situ tests(SPT, DCPT PMT, BST) and the end bearing capacity of drilled shafts were analysed. As a result, DCPT results were represented the best credibility. Also, a design chart of end bearing capacity using DCPT was suggested.

Case Studiy on Measurement of End Bearing Capacity for Large Diameter Drilled Shaft Constructed in Fault Zone using Loading Test (선단유압재하시험을 이용한 단층파쇄대에 설치된 대구경 현장타설말뚝의 선단지지력 측정 사례)

  • Jung, Chang-Kyu;Kim, Tae-Hoon;Jung, Sung-Min;Hwang, Kun-Bae;Choi, Yong-Kyu
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.74-81
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    • 2004
  • In this study, static end loading tests with load transfer measurement were accomplished for large diameter drilled shaft constructed in fault zone. Yield pile capacity (or ultimate pile capacity) from load-settlement curve was determined and axial load transfer behavior was measurd. The end bearing capacity was increased 2 times due to grouting the toe ground under pile base.

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End Bearing Capacity of a Pile in Cohesionless Soils (사질토에 있어서 말뚝의 선단부 지지력)

  • 이명환
    • Proceedings of the Korean Geotechical Society Conference
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    • 1988.06c
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    • pp.71-123
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    • 1988
  • The aim of this paper is to examine the end bearing capacity of a pile in cohesionless soils. The ode of failure of soil due to pile installation is assumed from experimental observation of actual soil deformation. A new solution is proposed complying with the assumed mode of failure by employing the theory of cavity expansion. The effect of curvature of failure envelope is studied in relation to tile proposed solution. The influence of a curved failure envelope becomes larger with increasing degree of curvature and the level of confining stress. This effect in some cases or reduce the end bearing capacity by tore the 80 percent compared with that given by a straight failure envelope. For practical application of tile proposed solution, the method of determining the average volume change in the plastic zone is re-evaluated. The proposed solution is confirmed by comparing the theoretical values with experimental results obtained from model pile tests in a calibration chamber. The comparison shows that the proposed solution provides a reasonable prediction of end bearing capacity for both weak and strong grained soils.

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Evaluation of Allowable Bearing Capacity of 600 mm Diameter Preboring PHC Piles Using Dynamic Load Test (직경 600mm PHC 매입말뚝의 동재하시험을 통한 허용 지지력 평가)

  • Woo, Gyu-Seong;Park, Jong-Bae;Seo, Mi-Jeong;Lee, Jong-Sub
    • Journal of the Korean Geotechnical Society
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    • v.32 no.11
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    • pp.61-72
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    • 2016
  • For the construction of high-rise structures and the optimized foundation design, the use of the large-diameter PHC pile has increased. Especially, the use of the 600 mm diameter PHC pile has significantly increased. In this study, for the evaluation of the suitability of the current design practice, the 46 dynamic pile load tests, which were carried out in the 600 mm diameter preboring PHC pile, are analyzed. The end bearing capacity is obtained from the end of initial driving test and the shaft capacity is estimated from the restrike test. The allowable capacities estimated by the dynamic load test are compared with those based on the current design practice. The analyses show that the allowable end bearing capacity evaluated by the dynamic pile load test is greater than the design practice in most piles. The allowable shaft capacity, however, is smaller than the design practice in many piles. The higher end bearing capacity and the smaller shaft capacity may result from the improvement of the drilling equipment and the increase in the penetration depth. Thus, the portion of the end bearing capacity in the total capacity increases.