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© Park 기초공학 lecture_05_pile_foundation
Pile Foundations
• dfd
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© Park 기초공학 lecture_05_pile_foundation
Pile Foundations
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© Park 기초공학 lecture_05_pile_foundation
Pile Foundations
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© Park 기초공학 lecture_05_pile_foundation
Load transfer mechanism
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© Park 기초공학 lecture_05_pile_foundation
Load transfer mechanism
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© Park 기초공학 lecture_05_pile_foundation
Load transfer mechanism
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© Park 기초공학 lecture_05_pile_foundation
Load transfer mechanism
5-10mm
10-25% of the pile width
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© Park 기초공학 lecture_05_pile_foundation
Base Capacity
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© Park 기초공학 lecture_05_pile_foundation
Base Capacity – Load-Settlement Curve
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© Park 기초공학 lecture_05_pile_foundation
Axial CapacitySingle Pile (Qp and Qs)Pile GroupNegative FrictionPull-out resistanceSettlement
Horizontal Capacity Single PilePile Group
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Outline of Pile Foundation
© Park 기초공학 lecture_05_pile_foundation
Axial Capacity of Single Pile
1. Equation 정역학적 공식2. Pile Load Test 말뚝재하시험3. Pile Driving Formula 항타공식4. Dynamic Test 동재하시험 (파동방정식 해석)
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© Park 기초공학 lecture_05_pile_foundation
1. 정역학적 공식
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© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) Pile Base Capacity in Sand
(or SPT)
2) Use measured CPT or SPT profile
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© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) Pile Base Capacity in Sand
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© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) Pile Base Capacity in SandMeyerhof
*'p p q p lQ A q N A q
*
1 160 60
0.5 tan '
0.4 4
l a q
l a a
a
q p NLq p N p ND
p in kPa
'tan2
2'45tan eNq
Note: Meyerhof’s Nq for shallow foundations
q’ = effective vertical stress
ql can be obtained from and SPT
ql
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L’/D: 16 - 18
© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) Pile Base Capacity in Sand
Additional EquationsVesic (1977)Janbu (1976)Coyle and Castello (1981)
Etc.
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© Park 기초공학 lecture_05_pile_foundation
Qp (Qb)
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qb는 qs에 비하여 큰 침하량이 발생한 후에 발현10%B 이상에서 발현되는 지지력은 의미가 없음
© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) in Sand
• 구조물 기초설계기준 해설– Nq
Note: Smaller than Nq* by Meyerhof due to cb
– L’ = 20 D
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Compare with
© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) Pile Base Capacity in Sand
CPT
SPTBriaud et al. (1985)Shioi and Fukui (1982)
LCPC method (page 521)Dutch method (page 522)
2) Use measured CPT or SPT profile
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60 60
60
60
30 300, 15,000
2, 100
p sq mN nN A
Lm where mN kPaB
n nN kPa
Meyerhof (1976)
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31: bymreducepilesntdisplacemenonfor
매입말뚝qb = 200 N60qb = 250 N60, N60<40
© Park 기초공학 lecture_05_pile_foundation
Qp (Qb) Pile Base Capacity in Sand
2) Use measured CPT or SPT profile
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60 60
60
60
30 300, 15,000
2, 100
p sq mN nN A
Lm where mN kPaB
n nN kPa
Meyerhof (1976)
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31: bymreducepilesntdisplacemenonfor
매입말뚝qb = 200 N60qb = 250 N60, N60<60
© Park 기초공학 lecture_05_pile_foundation
Qp Pile Base Capacity in ClayMeyerhof
* 9p p u c u pQ A s N s A when Fcs = 1.2, Fcd = 1.5
For clays, Qp = Qp,l=Qp,ult
Fcd
Fcs
Note: Meyerhof – Factors for Shallow Foundationwhen = 0
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