• Title/Summary/Keyword: Large diameter drilled shaft

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A Study on Lateral Loading the Field Test of Pile for Large Diameter Drilled Shaft Pile (대구경 현장타설말뚝에 대한 현장수평재하시험에 관한 연구)

  • Choi, Yong-Kyu;Lee, Min-Hee;Lee, Chung-Sook
    • Journal of the Korean GEO-environmental Society
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    • v.5 no.2
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    • pp.33-39
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    • 2004
  • Most of pile foundations are a condition of fixed head on pile, but lateral loading test of pile have performed to free head on generally. This study performed field lateral loading test accompanying lateral displacement by depth of pile for two cases(fixed head and free head) and analyzed lateral behavior of large drilled shaft. Furthermore compared theoretical equation with result of lateral loading test.

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Improvement of tip analysis model for drilled shafts in cohesionless soils

  • Chen, Yit-Jin;Wu, Hao-Wei;Marcos, Maria Cecilia M.;Lin, Shiu-Shin
    • Geomechanics and Engineering
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    • v.5 no.5
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    • pp.447-462
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    • 2013
  • An analysis model for predicting the tip bearing capacity of drilled shafts in cohesionless soils is improved in this study. The evaluation is based on large amounts of drilled shaft load test data. Assessment on the analysis model reveals a greater variation in two coefficients, namely, the overburden bearing capacity factor ($N_q$) and the bearing capacity modifier for soil rigidity (${\zeta}_{qr}$). These factors are modified from the back analysis of drilled shaft load test results. Different effective shaft depths and interpreted capacities at various loading stages (i.e., low, middle, and high) are adopted for the back calculation. Results show that the modified bearing capacity coefficients maintain their basic relationship with soil effective friction angle ($\bar{\phi}$), in which the $N_q$ increases and ${\zeta}_{qr}$ decreases as $\bar{\phi}$ increases. The suggested effective shaft depth is limited to 15B (B = shaft diameter) for the evaluation of effective overburden pressure. Specific design recommendations for the tip bearing capacity analysis of drilled shafts in cohesionless soils are given for engineering practice.

Axial Load Transfer Behavior of a Large Diameter Drilled Shaft by Osterberg Type Load Test (오스트버그식 재하시험을 이용한 대구경 현장타설말뚝의 축하중전이거동)

  • 임태경;정창규;정성민;최용규
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.447-454
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    • 2003
  • In this test, two separated oil jacks were placed at bottom of drilled shaft(D = 1,500mm, L = 33m), and maximum upward and downward load of 1,250 tonf was applied. Also, the deformable rod sensors were placed on each level, and axial strains at each level were measured. Because the side skin friction and the end bearing could be measured separately in the Osterberg type pile load test, this test might be more economical and more applicable than a conventional static pile load test. Thus, if this Osterberg type pile load test could be established during design stage, construction cost might be reduced and its application for large diameter pile could be enhance greatly.

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A Study on Estimation of Failure Probability of Allowable Stress Design using Reliability Analysis to the Bearing Capacity the Deep Water Depth Large-diameter Drilled Shaft (대수심 대구경 현장타설말뚝의 지지력에 대한 신뢰성 해석을 이용한 허용응력 설계의 파괴확률 평가 연구)

  • Han, Yushik;Lee, Yunkyu;Choi, Yongkyu
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.4
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    • pp.43-51
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    • 2014
  • A Large-diameter drilled shaft of deep water depth composite foundation supporting a high rise pylon of the test designed super long span bridge was designed by allowable stress design method and failure probability through reliability analysis to bearing capacity was estimated. The allowable stress design results for the bearing capacity of a drilled shaft were analyzed by reliability analysis and the probability of failure shows 0.12 % in case of CFEM, 0.0002 % in case of Korea Highway Corporation criterion, and 0.003 % in case of structure foundation design criterion. In the allowable stress design, the bearing capacity of a large-diameter drilled shaft was obtained by applying to safety factor 3 and reliability analysis for the results was done. If the failure probability suggested by AASHTO(2007) specification is set to 0.02 %, the socketed length of a drilled shaft shows an increase of 25 % in CFEM, decrease of 60 % in KHCC, and decrease of 89 % in SFDC.

Preliminary Load Tests for the Design of Large Diameter Drilled Shaft by Bi-directional Loading Method at Toe (대구경 현장타설말뚝의 설계를 위한 선단재하방법에 의한 시험말뚝 재하시험)

  • Song, Myung-Jun;Park, Yung-Ho;Kim, Dong-Jun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.89-98
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    • 2005
  • Preliminary pile load tests for the design of large diameter drilled shaft were performed on two of reduced scale(D=1370mm) test piles. The maximum loads of 2350 tonf in each direction were applied using bi-directional hydraulic jacks(Osterberg Cell) at toe. Neither of the test piles yielded in terms of skin friction and end bearing. Comparisons of the test results with several methods that estimate pile capacity show that the method of Horvath and Kenney(1979) for skin friction and Zhang and Einstein(1998) for end bearing were most appropriate for the site. The test results were directly applied to pile design in case RQD of skin and toe was larger than that of the test pile. It is desirable, therefore, to consider not only unconfined compression strength but also rock mass properties(i.e. TCR, RQD) for skin friction and end bearing evaluation in the future.

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A Case Study on Application of Bi-directional Pile Load Test for verifing the Bearing Capacity of a Large-diameter Drilled Shaft Pile (자갈층에 근입된 대구경 현장타설말뚝의 지지능력 확인을 위한 양방향 재하시험 적용사례)

  • Lee, Min-Hee;Jung, Sung-Min;Kim, Sang-Il;Choi, Yong-Kyu
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.506-513
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    • 2006
  • In this study, multi-level hi-direction pile load tests for drilled shaft pile socketed into the gravel were performed. The lower and upper hi-direction load test assemblies were located on tip of pile and 15m above the tip of pile. Based on the results of pile load test, it was analyzed bearing capacity of gravel, skin firction of upper soils and skin friction of lower soils. It was confirmed that drilled shaft socketed into the gravel had enough bearing capacity.

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Performance-based comparison of energy pile of various heat exchange pipe arrangement by in-situ thermal response test (현장 열응답 시험을 통한 에너지파일의 열교환파이프 배열 방식에 따른 성능 비교)

  • Min, Sunhong;Koh, Hyungseon;Yoo, Jaihyun;Jung, Kyoungsik;Lee, Youngjin;Choi, Hangseok
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.05a
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    • pp.196.1-196.1
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    • 2011
  • In this study, a test bed was constructed in order to evaluate thermal efficiency of the energy pile which carries out combined roles of a structural foundation and of a heat exchanger. The energy pile in this study is designed as a large-diameter drilled shaft equipped with the heat exchange pipes which configures a W-shape and an S-shape. The drilled shaft reached to the depth of 60 m whilst the heat exchange pipes were installed to about 30 m deep from the ground surface. The W-shaped and S-shaped heat exchange pipes were installed in the opposite sections of the same drilled shaft. In-situ thermal response tests were performed for both the shapes of heat exchange pipes. To avoid underestimating the thermal performance due to hydration heat of concrete inside the drilled shaft, the in-situ thermal response tests for the energy pile were performed after four weeks since the installation of the energy pile.

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Lateral Bearing Characteristics of Large Diameter Drilled Shafts by Casing Reinforcement Condition Using Non Linear Analysis (비선형해석을 이용한 케이싱 보강조건에 따른 대구경 현장타설말뚝의 수평거동특성)

  • Yoo, Jin-Ho;Moon, In-Jong;Lee, Kang-Il
    • Journal of the Korean Geosynthetics Society
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    • v.19 no.3
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    • pp.23-33
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    • 2020
  • The lateral bearing characteristics are important factors in the case of large diameter drilled shafts and the measures to increase this are to improve the adjacent ground of the pile to increase the rigidity and to increase the rigidity of the pile itself. There are many suggestions for increasing rigidity by reinforcing casing on the pile, but few studies have been done related to this. Therefore, in this study, the lateral bearing characteristics according to casing reinforcement length were studied for each ground condition using non-linear analysis to evaluate the appropriate casing reinforcement length of the large diameter drilled shafts depending on the ground conditions. As a result, the lateral bearing characteristics of the large diameter drilled shafts are most effective if the casing reinforcement length ratio is 1.2, and depending on the ground conditions, the more loose the ground, the greater the reinforcement effect.

Optimization of Reinforcement Effect of Large-diameter Drilled Deep Foundation (보강형 현장타설말뚝의 최적보강효과 분석)

  • 남대승;김수일;이준환;윤경식
    • Journal of the Korean Geotechnical Society
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    • v.19 no.2
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    • pp.207-216
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    • 2003
  • Drilled deep foundations of large diameter are often used for foundations of transmission towers. As tower structures become larger in modern society, there is a need of more efficient and economical design of large-diameter drilled deep foundations. Reinforced drilled deep foundations are popular in Japan for the foundation of tower structures. Stiffeners attached to the shaft of the foundation are used to increase the shaft resistance. This study aims at analyzing the effect of reinforcement with large-diameter drilled deep foundations based on numerical analysis of the representative soil and rock conditions in Korea. The numerical analyses are conducted to analyze the reinforcement effect of various stiffener conditions of number, inclination, location and length. Regarding to number of stiffeners, the effect of reinforcement for weathered and soft rocks increases proportionally as the number of stiffeners increases. For weathered soil, however, the effect of reinforcement increases at a lower rate. The effect of stiffener location is nearly negligible for axially loading cases, while it is significant for laterally loading cases. For the laterally loading cases, upper locations of stiffener give greater reinforcement effect than that of lower location. For stiffener inclinations of axial loading cases, a stiffener inclination equal to 60$^{\circ}$ gives the greatest reinforcement effect.

A Case Study of a Drilled Shaft Design and Construction of Buildings (건축구조물에서 현장타설말뚝에 의한 대형기초의 설계 및 시공사례)

  • Joeng, Gyeong-Hwan;Jung, Dong-Young;Kim, Young-Man;Jung, Sun-Tae;Kim, Dong-Jun;Kim, Min-Sung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.554-563
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    • 2009
  • The trend of current urban redevelopment and new city development project shows that the superstructure of building is getting larger and higher in consequence of a limited plottage condition. For this reason, it is definitely required to extend pile diameter and install more deep foundation(Mega foundation) to support superstructure. The existing precast pile construction method causes construction-related problems such as increasing quantities, difficulty of storage & transportation material and decreasing design load while construct pile in deep foundation. The drilled shaft method has applied to minimize those problems. This article will be presented construction case study of design & construction of R.C.D method for a large building foundation work on the inside and outside of the country.

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