Pile Foundation#1.pdf

7/21/2019 Pile Foundation#1.pdf

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Reg : 1.2.500.2.31.09.03.02978

Fondasi II

Luthfi Hasan

Deep foundation



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Prospek Teknik Sipil

! Bidang Pembangunan Infrastruktur

" Konsultan

" Kontraktor

! Bidang Pemerintahan

" Departemen/Dinas P.U

" Departemen ESDM

" Dinas Tata Kota" Bapenas, Bapeda

" Dinas Ketenagakerjaan



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! Bidang Industri Enerji & Pertambangan

" Manajer & CEO

" Quality Auditor

"

Quality Assurace Manager" Pertamina, PLN, freeport, Pupuk Kaltim

! Bidang Pendidikan

" Pengajar

" Peneliti

! Bidang lainnya

" Perbankan

" Asuransi

Prospek Teknik Sipil



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Yang harus disiapkan

! Penguasaan materi Teknik Sipil

!

Kemampuan digital/komputer

! Kemampuan bahasa Inggris minimal pasif

!

Soft skill/organisasi



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Bidang Teknik Sipil

! Struktur

! Geoteknik

! Transportasi

! Sumber Daya Air

! Manajemen Konstruksi



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SUCCESS

maksimal

SKS

HadirKuliah &

aktif

Penguasaan materi


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Proporsi penilaian

Penilaian

35 % UTS

50 % UAS

15 % kehadiran ! 10 kali

Target

pencapaian

!

Mengetahui dasar fondasi dalam

!

Mampu mendesain fondasi dalam

( pile foundation)



FOUNDATION ENGINEERING

(pile foundation)

Contents

! Pengertian Geotechnical Project

! Penentuan fondasi dangkal & dalam

! Jenis Pile foundations

! Mekanisme transfer beban pada pile foundations

! Pengertian kapasitas fondasi ( pile capacity )

!

Pile capacity di tanah non kohesif (sand )(end bearing & friction)

! Pile capacity di tanah kohesif (clay )

(end bearing & friction)

Part one :



FOUNDATION ENGINEERING

(pile foundation)

Contents

! Pile capacity berdasarkan data CPT dan SPT

!

Pemancangan ( pile driving)! Uji beban ( pile load test )

! Pile groups

! Penurunan (settlement of pile groups)

! Bored piles

Part two :



Main References

! Das, B.M. (2002). Principles ofGeotechnical Engineering, 5th edition,

Brooks/Cole Thomson Learning

! Das, B.M. (2004). Principles of FoundationEngineering, 5th edition, Brooks/Cole

Thomson Learning



Part One



Typical Geotechnical Project

construction site

Geo-Laboratory

~ for testing

Design Office

~ for design & analysissoil properties

Soil

mechanics



Shallow & DeepFoundations



FOUNDATION

load

Soil

Condition

Foundation



Shallow Foundations

bed rock

firmground

~ for transferring building loads to underlying ground

~ mostly for firm soils or light loads



Deep Foundations

bed rock

weak soil

P

I

L

E

~ for transferring building loads to underlying ground

~ mostly for weak soils or heavy loads



Perbedaan F. Dangkal & F. Dalam

F. Dangkal F. Dalam

D/B Kecil Besar

KeruntuhanSampai

permukaan

tanah

Di dalam

tanah

Instalasi DigaliDipancang/

dibor



Analisis jenis fondasi

B e b a n

Besar Kecil

L a p i s t a

n a h s t a b i l

D a l a m

D a n g k a l

FondasiDalam

FondasiDangkal

F. DalamF. Dangkal

F. Dalam

F. Dangkal



Pile Foundations



! Piles are relatively long and slender members used totransmit foundation loads through soil strata of low

bearing capacity to deeper soil or rock having a higher

bearing capacity.

! Pile resistance is comprised of

" end bearing

"

shaft friction

! For many piles only one of these components is

important. This is the basis of a simple classification

Pile Foundations



When one or more upper soil layers are highly

compressible and too weak to support the load

transmitted by the superstructure. Piles are used to

transmit the load to underlying bedrock or astronger soil layer

When bedrock is not encountered at a reasonable depth

below the ground surface, piles are used to transmit the

structural load to the soil gradually. The resistance to the

applied structural load is derived mainly from the

frictional resistance developed at the soil-pile interface

Use of pile foundations




When subjected to horizontal forces, pile

foundation resist by bending , while still

supporting the vertical load transmitted by the

superstructure

The foundations of some structures, such as

transmission towers, offshore platforms and basementmats below the water table, are subjected to uplifting

forces. Piles are sometimes used for these foundations

to resist the uplifting force




Bridge abutments and piers are usually areusually constructed over pile foundations to

avoid the loss of bearing capacity that a

shallow foundation might suffer because of

soil erosion at the ground surface



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Deep Foundations



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Pile foundation

Tall buildings needpiles down to the

rock bed to transferthe loads directly tothe solid part in theearth to avoiduneven settlement



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Jembatan Suramadu

Total panjang jembatan 5438m

Cable Stayed 818mApproach CausewayApproachCauseway

Sisi Surabaya Sisi Madura



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PONDASI CABLE STAYED BRIDGE

56 Tiang

100 m

15 m

100 m

20 m

Diameter 2.4 m



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Sutong Bridge - China

1088m

60m

Pondasi:

Panjang = 130m

Diameter = 3.2m - 60m pertama

2.8m - sisanyaJumlah = 131 tiang



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Piled Foundations



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Pile



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Jembatan Cikubang



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Jembatan Suramadu



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Ciujung



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Type of Pile Foundations



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Types of Piles

Concrete SteelPipe

Timber Steel H Pre-castConcrete

Composite



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Steel piles!

Discription" Usual length 15-60 m

" Usual load 300-1200 kN

!

Advantages" Easy to handle with respect to cut off and extension to the

desired length

" Can stand high driving stress

" Can penetrate hard layers

" High load-carrying capacity

!

Disadvantages" Relatively costly

" High level of noise during driving

" Subject to corrosion

" H-piles may be damaged or deflected during driving throughhard layers



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Concrete piles

! Precast piles

" Using ordinary reinforcement

" Prestressed : using high-strength steelprestressing cable

! Cast-in-situ piles



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Concrete piles

!

Discription" Usual length 10-15m (press : 10-45m)

" Usual load 300-3000 kN (press : 7500-8500 kN)

!

Advantages

" Can be subjected to hard driving" Corrosion resistant

" Can be easily combined with a concrete superstructure

" High load-carrying capacity

!

Disadvantages

" Difficult to achieve proper cutoff

" Difficult to transport



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Steps in Rational Pile Selection

! Adequate Subsurface Investigation

! Soil Profile Development

! Appropriate Lab/Field Testing

! Selection of Soil Design Parameters

! Static Analysis

! Applied Experience



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Deep foundationtype

Typical range ofnominal (ultimate)resistance (kips)

Typical length(feet)

Timber pile 75 – 200 20 – 40

Concrete pile 200 – 2,000 20 – 150

Steel H-pile 200 – 1,000 20 – 160

Pipe pile 175 – 2,500 20 – 100

Drilled shaft 750 – 10,000 20 – 160

Load Magnitude



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A Driven Pile is a deep

foundation that is constructed

by driving a concrete, steel or

timber pile to support the

anticipated loads in competent

subsurface material.

What is a Driven Pile?



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Driven Low Displacement Piles



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Driven High Displacement Piles



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Drilled Shafts (bored piles)



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Driven & Bored Pile

Jenis Keunggulan Kekurangan

Driven pile(Precast pile)

Kualitas terjamin

Dynamic pile capacity

Pelaksanaan singkat

Displacement pile

Human error kecil

Vibrasi saat driving

Bored pile(cast insitu)

Tanpa vibrasiNon displacement pile

Kualitas perlu ketelitian

Non dynamic pile capacityPelaksanaan cukup lama

Human error relatif besar



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Type of piles based on installation

! Non displacement pile (bored pile)

! Displacement pile ( driven pile)

! Extra displacement pile ( franki ple)



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Pile capacity



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Embedded

Length= D

Qu = Ultimate Bearing Capacity

Qs = fAs

f = Unit FrictionalResistance

AS = Shaft Area

qP = Unit Bearing

Capacity

AP = Area of Point

QP = qPAP

Ultimate Bearing Capacity -

Static Formula Method (Qu = Qp + Qs)



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Qu = Qs+Qp

Layer 4

Layer 3

Layer 2

Layer 1L1 QS1

Qp

L2 QS2

L3 QS3

L4

QS4

Qu



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END BEARINGLOAD

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D

SANDS

SOFTCLAYS

ROCK

LOA

LOAD

L O A D

SANDS

CLAYS

FRICTION

L O A D

SANDS

CLAYS

SAND

End Bearing or Friction?



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End Bearing Side Friction Combined

Method of Support



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Mekanisme trasfer beban

! Tahanan friksi (gesekan permukaan) termobilisasi penuh jika telah terjadi displacement sebesar :

! 5-10 mm (0,2-0,3 inch)……………..B.M. Das

! 0,30 – 1% lebar/diameter tiang …..Tomlinson

! Tahanan ujung termobilisasi penuh jika telah terjadidisplacement sebesar

! 10-25% lebar/diameter tiang ……….B.M. Das

! 10-20% lebar/diameter tiang ……….Tomlinson



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Ultimate Bearing Capacity -

Static Formula Method

Embedded

Length= D

Qu = Ultimate Bearing Capacity

Qs = fAs

f = Unit FrictionalResistance

AS = Shaft Area

qP = Unit Bearing

Capacity

AP = Area of Point

QP = qPAP

Qu = Qp + Qs



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End Bearing Piles

ROCK

SOFT SOILPILES



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Friction Piles

SOFT SOILPILES

Strength

increases

with depth



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Mekanisme keruntuhan

Terzaghi Meyerhof Vesic Skempton



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Luthfi Hasan (1998)



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Arching at Pile TipGround Surface

Arching Action

B

Df

$DfPO = %$Df

Zone of

Shear &VolumeDecrease



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! Combinations of vertical, horizontal and momentloading may be applied at the soil surface fromthe overlying structure

! For the majority of foundations the loads appliedto the piles are primarily vertical

! For piles in jetties, foundations for bridge piers,tall chimneys, and offshore piled foundations thelateral resistance is an important consideration

! The analysis of piles subjected to lateral andmoment loading is more complex than simplevertical loading because of the soil-structureinteraction.

Loads applied to Piles

V

M

H



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Estimation of Pile Capacity



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Tahapan desain

! Mengusahakan data tanah melalui soil investigation,berupa :

- Cone Penetration Test (CPT = Sondir)

- Standard Penetration Test (SPT)

- Boring (pengambilan sampel tanah)

!

Melakukan survei tentang kedalaman fondasi tiang padabangunan sekitarnya



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Tahapan desain (lanjutan)

!

Melakukan estimasi kapasitas fondasi tiang tunggalmenggunakan static formula, berdasarkan data:

- Cone Penetration Test (CPT)

- Standard Penetration Test (SPT)

- Hasil uji laboratorium

- Korelasi dari berbagai data diatas

!

Melakukan estimasi kelompok tiang berdasarkan hasilestimasi tiang tunggal dan beban kolom yang harus

ditahan



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Tahapan desain (lanjutan)

! Melaksanakan pile driving dengan menggunakandynamic formula berdasarkan estimasi nilai static

formula. Menentukan kapasitas tiang yang digunakan

! Melaksanakan pile load test bagi fondasi tiang yang

meragukan.



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Estimasi kapasitas tiang

)W(QQQ s pu !+=

ss p pu q.Aq.AQ +=

2

ss

1

p pall

SF

q.A

SF

q.AQ +=

Tahanan ujung end bearing)

Tahanan friksi (friction resistance)Unit daya dukung

Unit tahanan friksi

Angka keamanan untuk tahananujung

Angka keamanan untuk tahanan friksi

Qp

Qs

qp

qs

SF1

SF2



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Menghitung tahanan ujung (end bearing)

p p p q.AQ =

!!++= N..B.4,0 N N.c.3,1q q

_

cu q

!!++= N..B.3,0 N N.c.3,1q q

_

cu q

dsqdqsq

_

cdcscu F.F. N..B.5,0F.F. NqF.F. N.cq !!!!++=

Terzaghi

Square footing

Circular footing

Meyerhof



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Menghitung tahanan ujung (end bearing)

**q

_ *c p N.B. N. N.cq q

!!++=

Deep foundation

General equation

**q

*c N, N, N !

Bearing capacity factors

0 N.B. *

!" "Nilai B atau D kecil

*q

_ *c p N. N.cq q+=Sehingga :

) N. N.c(AQ *q

_ *c p p q+=

DAYA DUKUNG AKSIAL



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DAYA DUKUNG AKSIAL

Qu

= Qp

+ Qs

Qp

Qs ="2&r #l (% C)+ "2&r #l (k 'v tan()

. S . F Q

Q u all =

=Ap(c Nc +q Nq)

#l

'v

) 'v

Bearing Capacity Factors for Deep Foundations (Meyerhof, 1976)



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! "! #! $! %! %&

#

"

%

'

("!

#!

%!

'!

(!"!!

#!!

%!!

'!!

(!!

"!!!

) *

+

,-./ 12.34.-* )*5/67 8 9+65:



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Tahanan ujung tiang pada tanah pasir

Tanah pasir c = 0 , sehingga :

*q

_

p p N..AQ q=

Meyerhof ’s

Method :

! "= hq _

p p p q.AQ =

L=LB L

LB

Loose

Dense



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Tahanan ujung tiang pada tanah pasir

q p akan naik sejalan dengan naiknya LB dan akan maksimum pada :

critic

BB

D

L

D

L!"

#$%

&=

Dibawah (Lb/D)cr digunakan qp

Diatas (Lb/D)cr digunakan qp = qL (limit/batas)

L p*q

_

p p q.A N..AQ q !=Sehingga :

!= tan. N.50q *qL

!= tan. N.5q *qL

!= tan. N.1000q *qL

kN/m2

T/m2

lb/ft2



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Menghitung tahanan friksi (friction)

! "= f .L. pQsGeneral :

p = perimeter (keliling tiang)

#L = unit panjang tiang

*p. #L = luas selimut tiang

f =qs = unit tahanan friksi

!"= tan..K f '

v

K = Koefisien tekanan tanah

'’v = Tegangan efektif vertikal pada kedalaman yang

ditinjau, dianggap konstan setelah kedalaman 15D

(Meyerhof) atau 10D (Schmertmann)

( = Sudut gesek permukaan (tan( = µ)

DAYA DUKUNG AKSIAL



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DAYA DUKUNG AKSIAL

Qu = Qp + Qs

Qp

Qs = "2&r #l (k 'v tan()

. S . F Q

Q u all =

=Ap(c Nc +q Nq)

#l

'v

) 'v



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Nilai K :

Metoda instalasi K

Tiang pancang, displacement besar (1-2)Ko

Tiang pancang, displacement kecil (0,75-1,75)Ko

Bored pile (0,75-1)Ko

Ko = 1-sin+

Nilai ( :

Interface (

Baja halus (0,5-0,7) +

Baja kasar (0,7-0,9) +

Precast concrete (0,8-1) +

Cast in place +

Nilai K dan (



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Menghitung tegangan effektif (' v )

'’v akan naik sejalan dengan kedalaman tiang

hingga mencapai kedalaman L’ = 15D (asumsi,

tergantung dari nilai +, Cc dan Dr), selanjutnya

konstan.



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Tahanan ujung tiang pada clay (lempung)

) N. N.c(AQ *q

_ *c p p q+=

Tanah lempung : + = 0 ; kecil Nq q

_

! 9 Nc =

u p p c.9.AQ =

cu = undrained cohesion



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Menghitung tahanan friksi (friction)

Banyak metoda diperkenalkan untuk mencari tahanan

friksi pada lempung : Metoda %, metoda , dan metoda -

Metoda % uu S.c.f !=!=

f = unit friksi ; % = adhesion factor ;

cu = undrained cohesion ; Su= undrained strength

% dicari dengan beberapa cara, yang banyak digunakan

adalah API (American Petroleum Institute, 1981) dan

Randolph & Murphy (1985)

DAYA DUKUNG AKSIAL



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DAYA DUKUNG AKSIAL

Qu = Qp + Qs

Qp

Qs ="2&r #l (% c)

. S . F Q

Q u all =

=Ap.c Nc

#l



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Faktor penentu nilai%

! Konsolidasi tanah selama pelaksanaan

!

Dragdown lapisan diatasnya saat pemancangan

! Cara mendapatkan Su atau cu

! Tipe instalasi fondasi tiang

Menentukan %



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Menentukan %



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Nilai undrained shear strength (Su) :

C l a y Su (kPa) Su (kg/cm2)

Very soft 0-12 0-0,12

Soft 12-24 0,12-0,24

Medium 24-48 0,24-0,48

Stiff 48-96 0,48-0.96

Very stiff 96-192 0,96-1,92

Hard > 192 > 1,92

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