PILE FOUNDATION
Indra S. Harahap/ EVB4013 – VAB2073
PART I: INTRODUCTION TO PILE FOUNDATION
Indra S. Harahap/ EVB4013 – VAB2073
Scope of Pile Foundation Engineering • • • • •
Selection of Foundation Type Selection of Pile Type Single Pile Analysis Pile Group Analysis Quality Control and Quality Assurance
Indra S. Harahap/ EVB4013 – VAB2073
Nomenclature • Pile cap • Raker pile • Tie beam
Keywords: pile cap, piles, soft clay, sand, raker pile, batter pile Indra S. Harahap/ EVB4013 – VAB2073
Taxonomy (1) Application • Reduce Vibrations Problem
Solution
Keywords: tanks, silos, chimneys, machine foundations, sand, ground water, compaction piles, raked piles, damping of piles, small damping, vibrations Indra S. Harahap/ EVB4013 – VAB2073
• Improve Stability of Bridge Abutment
Keywords: soft clay, fill, bridge abutment Indra S. Harahap/ EVB4013 – VAB2073
• Embankment Pile
These piles, not soft clay, carry fill load and transfer the load to bearing layer.. Therefore, no horizontal forces carried by abutment piles.
Keywords: soft clay, raked piles, bridge abutment, fill Indra S. Harahap/ EVB4013 – VAB2073
• Anchor piles as for dry docks
Uplift hydraulic pressure
Keywords: ground water, up-lift force, anchor piles Indra S. Harahap/ EVB4013 – VAB2073
• Offshore Structures on Piles
Keywords: cyclic loading, scour, compression, steel pipe piles, tension force Indra S. Harahap/ EVB4013 – VAB2073
• Stabilization of Slope by Piles
Keywords: slope stability, large diameter pile, steel pipe pile, failure surface Indra S. Harahap/ EVB4013 – VAB2073
• Stabilization of Slope by Piles
Keywords: failure surface, clay, precast piles, Indra S. Harahap/ EVB4013 – VAB2073
• Anchor Piles in Swelling Soil
Keywords: seasonal changes, swelling clay, montmorillonite, high liquid limit, high plasticity index, building Indra S. Harahap/ EVB4013 – VAB2073
(2) Based on material •Concrete pile •Steel pile •Timber pile
Keywords: concrete pile, steel pile, timber, H pile Indra S. Harahap/ EVB4013 – VAB2073
Concrete pile • Precast Concrete Pile
Keywords: point, concrete, reinforcement. pile diameter Indra S. Harahap/ EVB4013 – VAB2073
• Prestressed Concrete Piles
Keywords: height strength concrete, brittle, reduced cracking, reduced ductility Indra S. Harahap/ EVB4013 – VAB2073
• Concrete strength
Keywords: cube strength, hard driving, normal to easy driving, high capacity, reduced weight, easy driving Indra S. Harahap/ EVB4013 – VAB2073
• Lifting of precast piles
Keywords: pile length, lifting hooks, moment Indra S. Harahap/ EVB4013 – VAB2073
Steel Pile • Steel H-Pile
Large contact area, high Qs
Keywords: easy to drive, easy to cut, corrosion, expensive, splicing, soil plug, driving shoe, steel plate Indra S. Harahap/ EVB4013 – VAB2073
• Steel Pipe Piles
Keywords: diameter, closed or open ended, soil plug, diameter Indra S. Harahap/ EVB4013 – VAB2073
• Steel corrosion
Keywords: steel piles, concrete piles, National Bureau of Standards, splices, reinforcement, salt water Indra S. Harahap/ EVB4013 – VAB2073
Timber Piles •
Characteristics
Keywords: advantages, difficulties, limit bearing capacity, soft clay, tip, shaft, ground water, butt Indra S. Harahap/ EVB4013 – VAB2073
• Pile splices
Keywords: steel sleeve, steel strap Indra S. Harahap/ EVB4013 – VAB2073
(3) Disturbance to Surrounding Soil
Keywords: large displacement piles, small displacement piles, non-displacement piles, bored piles, precast piles, pipe piles, cased, uncased Indra S. Harahap/ EVB4013 – VAB2073
(4) Loading Conditions of Piles
Keywords: compression, lateral load, tension Indra S. Harahap/ EVB4013 – VAB2073
(5) Load Transfer Mechanism Resistance of friction pile or floating pile mostly comes from friction resistance. Even though there is a point resistance, since the pile is not founded into a firm-bearing layer the point resistance is very small. In contrary, end bearing or point bearing pile, the pile resistance particularly come from point resistance. Keywords: friction or floating piles, end bearing piles, clay, sand, rock Indra S. Harahap/ EVB4013 – VAB2073
Splices and Rock Points
Keywords: rock point Indra S. Harahap/ EVB4013 – VAB2073
(6) Based on Installation Method • Driven Pile • Bored Pile • Jacked-Down Pile
Indra S. Harahap/ EVB4013 – VAB2073
Driven pile • Installation method
Indra S. Harahap/ EVB4013 – VAB2073
• Settlement during driving in sand
Keywords: settlement, diameter, compaction within this zone Indra S. Harahap/ EVB4013 – VAB2073
• Settlement during driving in clay
Keywords: soft clay, heave, volume, soft clay, remoulded zone, pore water pressure, undrained shear strength Indra S. Harahap/ EVB4013 – VAB2073
• Redriving of pile in clay
Keywords: risen piles, redriving, heave, soft clay, separation of splice Indra S. Harahap/ EVB4013 – VAB2073
Bored Pile • Installation method
Keywords: casing, driving, casing filled with water, casing filled with concrete, reinforcement Indra S. Harahap/ EVB4013 – VAB2073
• Installation method with casing for soft clay
Keywords: casing, driving, casing filled with water, casing filled with concrete, reinforcement Indra S. Harahap/ EVB4013 – VAB2073
• Necking during casting in soft clay
Keywords: casing, soft clay, sand or silt, ground water Indra S. Harahap/ EVB4013 – VAB2073
• Bored pile with bell
Keywords: bells Indra S. Harahap/ EVB4013 – VAB2073
• Installation using bentonite slurry
Keywords: ground water, surface casing, bentonite slurry, chisel, pouring of concrete, lowering of reinforcement element Indra S. Harahap/ EVB4013 – VAB2073
• Various shapes of slurry trench pile
Keywords: size, shape
Indra S. Harahap/ EVB4013 – VAB2073
Jacked-Down Pile • Installation method
Keywords: pump, manometer, steel insert, hydraulic jack, pile segment Indra S. Harahap/ EVB4013 – VAB2073
(7) Proprietary Pile • Raymond step tapered pile
Keywords: steel shell, steel cone, light bulb, reinforcement cage, casting of concrete Indra S. Harahap/ EVB4013 – VAB2073
• Franki pile
Keywords: concrete plug, bulb, internal hammer, prefabricated shaft, light casing Indra S. Harahap/ EVB4013 – VAB2073
PART II. PILE BEARING CAPACITY ANALYSIS
Indra S. Harahap/ EVB4013 – VAB2073
Pile Bearing Capacity • Single Pile • Pile Group
Indra S. Harahap/ EVB4013 – VAB2073
Pile Bearing Capacity of Single Pile • Compression capacity • Tension capacity • Lateral capacity
Keywords: compression, lateral load, tension Indra S. Harahap/ EVB4013 – VAB2073
Capacity of Pile Group • Efficiency • Group settlement
Indra S. Harahap/ EVB4013 – VAB2073
Issues Relating to Pile Capacity
Indra S. Harahap/ EVB4013 – VAB2073
• Load distribution along pile
Ultimate resistance of piles: For sand, shaft and point equally contribute to ultimate resistance For clay, shaft resistance dominated ultimate resistance
Keywords: sand, clay, point resistance, shaft resistance Indra S. Harahap/ EVB4013 – VAB2073
• Load vs. Displacement
Keywords: load, displacement, soft clay, stiff clay, sand, cast in place pile, driven pile, with bell Indra S. Harahap/ EVB4013 – VAB2073
• Load deformation relationship •Shaft resistance of soft clay and sand are fully mobilized, i.e. reach its maximum value, at relatively small pile displacement. •Point resistance is reached at relatively large pile displacement compare to shaft resistance. •Point resistance of large displacement piles (i.e. driven-pile) is mobilized relatively faster (at relatively small displacement) than non-displacement piles (i.e. bored-pile). This due to the fact that driven pile compacting soil close to the pile tip, and boredpile loosening soil close the pile tip due to stress release. However, for a certain cases driven pile could loosen soil close to the pile tip. For example, driving piles through very dense sand or highly over consolidated soil.
Indra S. Harahap/ EVB4013 – VAB2073
• Idealized load deformation relationship
Keywords: pile load, point resistance, skin resistance Indra S. Harahap/ EVB4013 – VAB2073
Pile Bearing Capacity Determination A. Analytical Method •
Based soil strength parameters obtained from laboratory test. Pile bearing capacity is established based on general bearing capacity equation of shallow foundation.
B. Empirical Method •
Based on field-testing method and empirical correlation from loading test. Empirical relationship has been developed between SPT, CPT and Swedish Sounding with pile bearing capacity.
C. Dynamic Method •
Based on observation during pile driving. Response during pile driving reflects soil resistance encounter by the pile. Pile ultimate resistance is determined taking into account pile driving equipment, response during pile driving and other soil parameters.
D. Pile Load Test Method •
Based on load deformation characteristic during pile loading test.
Indra S. Harahap/ EVB4013 – VAB2073
A. ANALYTICAL METHOD
Indra S. Harahap/ EVB4013 – VAB2073
A.1. Introduction (1) Direction of Pile Loading
Factor of Safety (FOS): FOS for compression differs than FOS for tension. FOS for shaft resistance differs than for point resistance. Point and shaft resistance for sand and clay determined differently.
Keywords: compression, tension, weight of pile, factor of safety, allowable load, point resistance, shaft resistance Indra S. Harahap/ EVB4013 – VAB2073
(2) End Bearing Capacity
Omitted because small compare to overburden
Keywords: end bearing, undrained shear strength, bearing capacity factors Indra S. Harahap/ EVB4013 – VAB2073
• Bearing Capacity •Pile resistance for pile in sand mostly contributed by overburden pressure v. The following assumptions for determination of pile capacity in sand are: The friction angle exist and cohesion equal to zero (=, c=0) Pile length L, much bigger than pile diameter, as such the contribution of pile resistance from gamma is negligible. There are several bearing capacity factors Nq has been proposed:
Indra S. Harahap/ EVB4013 – VAB2073
• Meyerhof bearing capacity factor
Keywords: friction angle, bearing capacity factor Indra S. Harahap/ EVB4013 – VAB2073
• Various Bearing Capacity Factors
Keywords: Terzaghi, Berezantsev, Meyerhof, Vesic, Brinch Hansen, de Beer, friction angle Indra S. Harahap/ EVB4013 – VAB2073
• Failure mechanism for Vesic’s factor
Keywords: point resistance, rigidity index, failure surface, compressibility, rigidity index Indra S. Harahap/ EVB4013 – VAB2073
A.2. Pile Capacity in Sand (1) Bearing Capacity Equation
Keywords: loose, dense, coefficient of lateral earth pressure at rest, small, Vesic, displacement pile, nondisplacement pile, tapered pile
Indra S. Harahap/ EVB4013 – VAB2073
(2) Pile Shaft Capacity in Sand
Keywords: pile type, sand, critical depth,
Indra S. Harahap/ EVB4013 – VAB2073
(3) Lateral Pressure Against Pile Shaft
Keywords: bored pile, small displacement pile, large displacement pile, straight shaft, tapered shaft, lateral earth pressure Indra S. Harahap/ EVB4013 – VAB2073
• Controlling factors Lateral pressure exerted by soil on pile surface depend on the following factors: •Disturbance and the nature of disturbance to surrounding pile during pile construction. Driven pile cause compaction (loose to medium sand and soft to medium clay) or dilation (dense sand or overconsolidated clay. •The inclination of side (straight side or tapered).
Indra S. Harahap/ EVB4013 – VAB2073
• Empirical parameter for K
Keywords: Mansur & Hunter, Tavenas, Ireland, lateral earth pressure Indra S. Harahap/ EVB4013 – VAB2073
• Critical depth
Keywords: friction angle, bearing capacity value, diameter, length Indra S. Harahap/ EVB4013 – VAB2073
A.3. Pile Capacity in Clay (1) End resistance
Indra S. Harahap/ EVB4013 – VAB2073
(2) Shaft resistance
Keywords: normally consolidated clay, overconsolidated clay, undrained shear strength, reduction , ground surface
Indra S. Harahap/ EVB4013 – VAB2073
• Lambda-Method
Keywords: offshore structures, depth, mean value, skin resistance
Indra S. Harahap/ EVB4013 – VAB2073
• Empirical estimate of pile skin friction in clay
Keywords: effective overburden pressure, Flaate, Selnes, undrained shear strength
Indra S. Harahap/ EVB4013 – VAB2073
A.5. Other Consideration (1) Load Transfer Mechanism
Keywords: t-z curves, q-y curve, driven pile, bored pile Indra S. Harahap/ EVB4013 – VAB2073
(2) Negative Skin Friction
Keywords: lowering of ground water level, driven pile, bored pile
Indra S. Harahap/ EVB4013 – VAB2073
A.6. Summary Summary Soil Type
Point Resistance Q p q p Ap
Shaft Resistance Qs As f s
Sand
q p qN q' or 1 2 qp K o qN q' 3
f s K a v'
Clay
q p 9cu
Note:
K a depends on type of pile. Shaft resistance constant after reaching critical depth
f s c u f s v' f s ( v' 2cu )
Indra S. Harahap/ EVB4013 – VAB2073
B. EMPIRICAL METHOD
Indra S. Harahap/ EVB4013 – VAB2073
(1) Cone Penetration Test •
End resistance
Keywords: area of pile, sand Indra S. Harahap/ EVB4013 – VAB2073
• Shaft friction
Keywords: cone penetration test, friction sleeve small displacement pile, large displacement pile Indra S. Harahap/ EVB4013 – VAB2073
(2) Standard Penetration Test • N-Value vs. pile capacity
Keywords: SPT, sand, pile diameter Indra S. Harahap/ EVB4013 – VAB2073
(3) Weight Sounding Test (WST) • Estimate of Pile Capacity Based
Keywords: half-turns, timber piles, concrete piles, Norwegian Pile Commission, s Indra S. Harahap/ EVB4013 – VAB2073
Laterally Loaded Single Pile
Indra S. Harahap/ EVB4013 – VAB2073
Failure Mode of Horizontally Loaded Piles
Indra S. Harahap/ EVB4013 – VAB2073
Lateral Pile Resistance in Sand
Indra S. Harahap/ EVB4013 – VAB2073
Lateral Pile Resistance in Clay (Rotational Mode)
Indra S. Harahap/ EVB4013 – VAB2073
Lateral Pile Resistance in Clay (Pile Failure Mode)
Indra S. Harahap/ EVB4013 – VAB2073