MINGGU 4 Daya Dukung Pondasi Dangkal Compatibility Mode

Daya Dukung (Bearing Capacity)

SIVA1

batuan (rock)

Tanah

kuat

Pondasi Dangkal

~ untuk melimpahkan beban ke lapisan di bawahnya~ utamanya untuk tanah kuat atau beban ringan

SIVA Copyright 20012

batuan (rock)

Tanah

kuat

Footing PerformanceFooting Performance

Vertical LoadVertical LoadV

e

r

t

i

c

a

l

m

o

v

e

m

e

n

t

V

e

r

t

i

c

a

l

m

o

v

e

m

e

n

t

ElasticElastic

PlasticPlasticmaximum tolerablemaximum tolerablesettlementsettlement

maximum servicemaximum serviceloadload

ultimateultimatecapacitycapacity

safe loadsafe load

SIVA Copyright 2001

V

e

r

t

i

c

a

l

m

o

v

e

m

e

n

t

V

e

r

t

i

c

a

l

m

o

v

e

m

e

n

t

PlasticPlastic

PlungingPlungingFailureFailure

Serviceability Limit StateServiceability Limit State

settlementsettlement

Ultimate Limit StateUltimate Limit State

Maximum allowable load =Maximum allowable load =min min [[safe load, max service load safe load, max service load ]]

Limit States


ServiceabilityServiceabilityServiceabilityServiceability UltimateUltimateUltimateUltimate

Bearing Pressure DefinitionsBearing Pressure Definitions

FFFF Plan Area, APlan Area, A

Bearing PressureBearing Pressure qqbb == F / AF / ASafeSafe qqss = = .q.quu / / AllowableAllowable qqaa < q< qss (settlement)(settlement)

SIVA Copyright 2001

FFFF Plan Area, APlan Area, A

Ultimate Bearing CapacityUltimate Bearing Capacity qquu == FFfailfail / A/ A

Foundation FailureFoundation Failure

ForceForceRotational FailureRotational Failure

SIVA Copyright 2001Soil HeaveSoil Heave ResistanceResistance

Pola Keruntuhan

General Failure


Local Shear Failure

Punching Shear Failure

General Failure


Local Shear Failure

Punching Shear Failure

FOUNDATION FAILURE1.Generalized Shear FailureFOUNDATION FAILURE1.Generalized Shear Failure

Soil FailureSoil Failure

qq

SIVA Copyright 2001

Soil FailureSoil FailureLinesLines

rigidrigidradialradialshearshear

passivepassive

log spirallog spiral

SettlementSettlement

2. Local Shear Failure2. Local Shear Failure

minor surfaceminor surface

qq

SIVA Copyright 2001

Medium denseMedium denseor firm soilsor firm soils

minor surfaceminor surfaceheave onlyheave only

SettlementSettlement

3. Punching Shear Failure3. Punching Shear Failure

qq

SIVA Copyright 2001

Loose orLoose orSoft SoilsSoft Soils

No surfaceNo surfaceheaveheave SettlementSettlement

Perhitungan Daya Dukung

Untuk menghitung daya dukung dapat dilakukan dengan analisisis berdasarkan :

Data Uji Laboratorium:Teori TerzaghiTeori Meyerhof


Teori MeyerhofTeori Brinch HansenTeori Vesic

Data Uji Lapangan :Plate Bearing TestCone Penetration Test/CPT (SondirStandard Penetration Test/SPT

Aplikasi Teori Daya Dukung

KEMIRINGAN TERZAGHI MEYERHOF HANSEN VESIC

BEBAN 0


MUKA TANAH

0 0

DASAR PONDASI

0 0

Daya Dukung Terzaghi

Anggapan-anggapan:1. Tanah homogen isotropik2. Mode keruntuhan pondasi adalah

adalah general shear failure3. Pondasi adalah strip dengan permukaan bawah kasar4. Bidang keruntuhan geser diatas permukaan tanah diabaikan


permukaan tanah diabaikan5. Permukaan tanah adalah horizontal6. Tidak terdapat gaya horizontal,

momen dan eksentrisitas7. Pondasi terletak pada kedalaman D

Keseimbangan Gaya


Keseimbangan gaya-gaya yang bekeja pada baji tanah (soil wedge) adalah:

Qu.(2b).1 = - W + 2.Csin + 2.Pp

1 212

= + +f c qq cN DN B N

Strip footing


1 212

= + +f c qq cN DN B N

Faktor Daya Dukung Tanah Menurut Terzaghidan Berbagai Nilai N yang Berbeda


Terzaghi Bearing EquationTerzaghi Bearing Equation

applies to strip footing Nc, Nq and N are functions of , and are

usually given in graphical form

qqu nettu nett = c.N= c.Nc c + p'+ p'o o ((NNqq -- 1) + 0.51) + 0.5BB'N'N

SIVA Copyright 2001

usually given in graphical form c, and ' refer to soil properties in the failure

zone below the footing p'o is the effective overburden pressure at the

founding level shear strength contribution above footing level

is ignored : conservative for deeper footings

Terzaghi Bearing EquationTerzaghi Bearing Equation

qqu nettu nett = c.N= c.Nc c + p'+ p'o o ((NNqq -- 1) + 0.51) + 0.5BB'N'N

SIVA Copyright 2001

Bp'p'o o = = ''oo DD

Generalized soil strength : c, Generalized soil strength : c, (drainage as applicable)(drainage as applicable)

Soil unit weight : Soil unit weight : '' (total or(total oreffective as applicable)effective as applicable)

Overburden

Failure Zone (depth 2B)

Adopt weighted average values !Adopt weighted average values !

Bearing Capacity Factors


Faktor daya dukung Terzaghi

pi

aN

ea

q

tg

)45(cos2 22

)24

3(

+=

=


tgNNjikaN

ctgNN

q

c

qc

).1(20:7,5

).1()

245(cos2 2

+=

==

=

+

Faktor daya dukung Terzaghi

pi

ctgNN

tgeN

qc

tgq

).1()

245(2.

=

+=


tgNNjikaN

ctgNN

q

c

qc

).1(20:7,5

).1(

+=

==

=

Faktor Daya Dukung


Bearing capacity factors

Rumus Umum Daya Dukung

Secara umum daya dukung dapat ditulis sbb:

qu = c.c Nc + q. D.Nq + .0,5 B.N


qu = c.c Nc + q. D.Nq + .0,5 B.Ndimana:

c, q, = faktor koreksi yang tergantung pada bentuk,kedalaman,kemiringan: beban, muka tanah, dasar pondasi

Faktor Daya DukungFaktor Daya Dukung

10001000

100100

B

e

a

r

i

n

g

C

a

p

a

c

i

t

y

F

a

c

t

o

r

B

e

a

r

i

n

g

C

a

p

a

c

i

t

y

F

a

c

t

o

r

NcNcNqNq

NNqq = 33= 33NN

NN = 250= 250

SIVA Copyright 2001

1010

11

0.10.100 1010 2020 3030 4040 5050

B

e

a

r

i

n

g

C

a

p

a

c

i

t

y

F

a

c

t

o

r

B

e

a

r

i

n

g

C

a

p

a

c

i

t

y

F

a

c

t

o

r

Friction Angle (deg)Friction Angle (deg)

1414oo

NNcc = 10= 10

3535oo 4646oo

Persamaan Daya Dukung MeyerhofPersamaan Daya Dukung Meyerhof

qquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = = cc.N.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BBNNssddiiqquu = c.N= c.Nccssccddcciicc + + qq.N.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddiiqquu = c.= c.NNccssccddcciicc + q.+ q.NNqqssqqddqqiiqq + 0.5+ 0.5BBNNssddiiqquu = c.N= c.Nccssccddcciicc + q.N+ q.Nqqssqqddqqiiqq + 0.5+ 0.5BNBNssddii

SIVA Copyright 2001

cc

soil density, soil density, , , ((kN/mkN/m33))BB

DDff q = q = .D.Dff

Bearing Capacity Factors for soilBearing Capacity Factors for soilcohesion, surcharge and weightcohesion, surcharge and weight

functions of friction angle, functions of friction angle, determine by equation or from graphdetermine by equation or from graph

Correction factors for footing shape Correction factors for footing shape ((ss)),,footing depth footing depth ((dd) ) and load inclination and load inclination ((i i ).).

determine from appropriate equationsdetermine from appropriate equations

Faktor daya dukung Meyerhof

).1()

245(2.

pi

ctgNN

tgeN

qc

tgq

=

+=


).4,1().1(0:14,5

).1(

tgNNjikaN

ctgNN

q

c

qc

=

==

=

Faktor daya dukung Hansen

pi

ctgNN

tgeN

qc

tgq

).1()

245(2.

=

+=


tgNNjikaN

ctgNN

q

c

qc

).1(5,10:14,5

).1(

=

==

=

Faktor daya dukung Vesic

pi

ctgNN

tgeN

qc

tgq

).1()

245(2.

=

+=


tgNNjikaN

ctgNN

q

c

qc

).1(20:14,5

).1(

=

==

=

Pengaruh Muka air


Pondasi dengan Beban MomenPondasi dengan Beban Momen

P

M

eP

SIVA Copyright 2001

e

e = MPekivalen eksentrisitas beban

Cara Meyerhof menentukan eksentrisitas beban

Cara Meyerhof menentukan eksentrisitas beban

ee

L

SIVA Copyright 2001

PP

ee

2e LL' = LL-- 22ee

B

Eksentrisitas 2 arahEksentrisitas 2 arah

ee11

LL

22ee22

SIVA Copyright 2001

PP

ee11

22ee11 LL' = LL-- 22ee11

BB ee2 2

B B

'

=

B B

- -

2 2

e e

2 2

Daya Dukung Berdasar Data Uji Lapangan (In Situ Test)

Plate Bearing Test (Uji Pembebanan Pelat)Standard Penetration Test (SPT)


Standard Penetration Test (SPT) Cone Penetration Test/CPT

(Sondir)

Plate Load Tests


Plate Bearing Test(Uji Pembebanan Pelat)

Tanah dengan kekuatan konstanB < 4 Bp

Tanah Dengan Kekuatan Meningkat puu qq ,=


Tanah Dengan Kekuatan Meningkat Secara Linear Thd Kedalaman

B < 4 Bp Ekstrapolasi Hasil Uji Penurunan

Terzaghi & Peck.

ppuu B

Bqq,

=

iqq 5,11

=

Standard Penetration Test (SPT)

PONDASI TELAPAK (FOOTING)MEYERHOF (1956,1974)

Dimana :qa,1 = daya dukung ijin utk penurunan 1 inchi

dn

a KFNqftB

11,4 =

23

21,4

+=>

BFB

FNqftB na


qa,1 = daya dukung ijin utk penurunan 1 inchiKd = 1+0,33 D/B1,33Nn = SPT yang dikoreksiF = faktor tergantung energi pukulan SPT

PONDASI PELAT (MAT/RAFT)d

na KF

Nq3

1, =

1,aa qq =

Cone Penetration Test/CPT(Sondir)

SCHMERTMANN (1978) DAYA DUKUNG BATAS PADA TANAH NON

KOHESIF

MENERUS : qu = 28 0,0052(300-qc)1,5


u c

BUJUR SANGKAR : qu = 48 0,0090(300-qc)1,5 DAYA DUKUNG BATAS PADA TANAH KOHESIF

MENERUS : qu = 2 + 0,28 qcBUJUR SANGKAR : qu = 5 + 0,34 qc

qu dan qc dalam tsf atau kg/cm2

Belajar


Jangan tunggu sampai menit terakhir.

Exams

My mama always said, Exam is like a box of chocolates; you never know what you


of chocolates; you never know what you are gonna get

MINGGU 4 Daya Dukung Pondasi Dangkal Compatibility Mode

Documents

Transcript of MINGGU 4 Daya Dukung Pondasi Dangkal Compatibility Mode