REKAYASA PONDASI

KONTRAK BETAJAR1) Perkuliahan

TUGAS DI KELAS +ASISTENSI = 25o/o

Terlambat lebih dari 20 menit, mahasiswa tidakdiperbolehkan masuk ke kelas.

TUJUAN INSTRUKSIONALUMUMMahasiswa dapat menguasaidasardasar perhitungan kapasitasdaya dukung, besarnya penurunan,dan gaya-gaya yang bekerja padapondasi dangkal dan dalam untukd iterapkan pada PERANGANGANPONDASI DANGKAL danPONDASI DALAi'I-

Sipillhla 2(X)6-Pqe3i:.

MATERT KULTAH (1)1) Pendahuluan : jenis-jenis

pondasi2) Daya dukung pondasi

dangkal berdasarkanparameter tanah hasil ujilaboratorium : Daya DukungTerzaghi, Meyerhof &Brinch Hansen

3) Daya dukung pondasi dangkal berdasarkan' parameter tanah hasil uji lapangan : CPT &

' 4) Perancangan Pondasi Dangkal +Perhitungan Settlement

SifillbnG 2)06 -Page4

2

MATERT KULTAH (215) Jenis dan penggunaan

pondasi dalam.6) Daya dukung aksial pondasi

dalam berdasarkanparameter tanah hasil ujilaboratorium.

7) Daya dukung aksial pondasi dalam berdasarkanparameter tanah hasil uji lapangan : CPT &SPT.

8) Daya dukung aksial pondasi dalamberdasarkan hasil uji pembebanan di

, lapangan.Siid lbnas 2006

- Page 5

MATERT KULTAH (219) Perancangan Pondasi

Dalam : daya dukungkelompok tiang &settlement.

Sitillbn6 An6-P{eo

3

PENDAHUU.,AN

. STRUKTUR PONDASI : fugian/elernan struktur(biosorryo terletak palirg bawah dori suotu bongunan) yongberfungsi menstronsfer/memindohkon/menyolurkon bebon-bebonloin dqri strukfur bangunon tersebut (superstructure) don beratsendiri struktur pondosi ke dolom tonoh otou batu pondasi.

TANAI{ ATAU BATU PONDASI : Tonah otou botu yong tnenerinobeban-bebqn dari sfruktur pondosi.

Terdapot perbedoon kekuaton ontoro tonah pondosi dengon strukturofos (superstructures) sehinggo diperlukon struktur pondosi untukmenyeborkon bebqn dori struktur atas (superstrtctures) ke tonahpondasi yang lebih lenoh dibanding struktur otds (super structures).

Sipilltenas 2006 -

P4e 7

. KEKUATAN TANAH BERUBAH-UBAH SESUAI DENoAN \AJENIS DAN KONDTST rANAI{ rru. \N

. JENIS TANAH : Tonoh kohesif (Cohesion Soil) seperti lempung t"f"Ndon tonoh tidok kohesif (Cohesionless soil) seperti posir. \

. KONDISI TANAH : Tonoh tidak jenuh oir don tanoh jenuh oir(soturated soil).

. Tonoh pondosi mempunyai sifot KEttiAirlPATAN yong songotbesar dibonding bojo don beton karena tonoh menpunyai poriyang besor sedongkon baja dan beton harnpir tidok mernpunyaipori.

KLASIFIKASI TANAH BERDASARKAN DIAIAETER BUTTR I1. Lempurg (Cloy) : very soft, soft, mediunr stiff. stiff, hord, very hord2. Lnnou (Silt) : very soft. soft, medium stiff. stiff, hard, very hard3. Posir (Sand) : very loose, loose, medium dense. dense, very dense4. Kerikil(6ravel):

5. Botu (Rock) : A,B,C, D class.

KLASIFIKASI TAMH BERDASARKAN DIAIAETER BUTIR :

i ] ffr r,;r {irr,ASI M U.i::.r,1 I n..,r,rirl ilq,; 1,,1..x | ,1,."6 " "-

l- __ ni,,!:, . .

.H!.rr , _ rNvl.rr,ridic g t f ,r, F;'i: j : _; r :

a

Sipit ltena 2006 -

Page 9

JE].1[5-JE]dI5 STRUKTUR PONDASI1. Berdasorkon kedolomon. Stnrktur pondosi dcngkol : jiko kedohman (Dt) : lebor (B),

kedqlomon : 3 sompoi 4 koli lebor telah disorankon fermosukpondosidorykal.

. Struktur pondasi dolon : kedElomon lebih dori 4 koli lebor sirukturpondosi

2. Berdasorkan Cara Pemindohan Beban. Stnukfur pondasi langsurg dan plot (spreod footing ond rofts). Sfrukfur pondosi riarg (pile foundation). Strukfur pondosi bore pile (drilled pier foundation)

3. Berdosorkcn Bohon/llioferiol. Kctu/ Timber, contohnyc struktur pondosi pendopo (rutnoh di Jowo),

struktur pondci rurroh ponggung di NTBBatu/stone masonry, contohrrya struktur pondosi rumoh

concrste, contohnyc untuk gedurg, pobrik, tnnoro, jembcton.ialsteel, contonyo unfuk kilcng minyok, pipa nirryok, gos, dermago,

Sipil lten6 2006 -

Page 10

CONTOH.CONTO}I PEI.TILIHAN JENIS PONDASIa Fcrdlbr Fnd M',

- fr-

.n-- -T!t------;--T'

ili I I -.

ry x,il,-rmt! I i lhr:i il I I :_-l-*,#-#.

tulr ks ht.rl,n P.!#' rde.li! risF! t#r! rtwlr\! rdr$

Ci.,{.! (:ffi Fia.d ldr ktb l.iattlt8 to{irdbr& Elid lP i * !.d idde b.nl'

&b ni{r8n( S d* lMi{{uud,n rdgrtffiM

:$*^_..IEgfi-**rlrqe s,!6 rq Thq lq;;:6;; dr M bs F4.&rh,i"^'*, l.tr ht k@l

' dreMju(*. aJ Cld rdd Ua. b?lnr Fidrrq Fcd

., !db-4rfiht6Ehnld.

Xll*@b ts lqb&lharM hF !aqdh-6uS*!!1 ii t6P

f&, {a C*l Frd.d Hr }illd ldar8f tddsilnJr i{*k 3t r I LiJr Fndle ffd' Sipil lbnc 2006

- PAe 11

CONTOH PONDAS|I DA}.lIilL : podosi lorynng ctor

5 Podc; Telapa*

ffiffiffi'o'

t;ffirnTnT

ffiffirrF*-Tn F.;:-:;:;1F$==+fi li'fi"- l'ilffi l,i,,.=*i

ld) Tunpd Fl,.llRdil6otit*l

Cb.5,2 J6* roed !.lrf.k

Si$l lbes ZD6 -

P4e 12

2

POIIDASI TIAlrl6nILE FOUNDATION

Pondasi tiarg/pile odqloh suotu jenis pondosi dalonmenstronsfer/ memindohkon/menyclurkanstruktur bongunon otos (superstructure) tersebut kepondosi tonpc risiko keruntuhon okibot geser (shearpenurunon yong berlebihan (excessive settlemenf).

Pondosi jenis pile digunokon jikc beban-beban hin dbcngunon yang okan ditronsf erldipi ndahkcn/d isolurkon kapondosi rnelalui suotu lapisan tonah lemoh (weok soil) otoutanoh yarg nrudoh tnemompot (compressible soil) otau oir.

lAocan-nocon Pondasi Tiangr' Pile1. Berdosorkon motarial t ster;|, concrete, titnber2. Berdossrkon bentuk : bulat, bujur songkor, se.gi

segitigc3. Berdosdrkon goyo : and beoring pile, friction pile4. Berdasorkan caro kerjo : single pile. group pile.

3

PONDASI BC'R / BORE PIIE FA'NDATION/DRIIIED PIERPondosi bor/bore pile foundotion adoloh suotu jenis pondosi dolomyang berfungsi menstronsfer/ memindahkon/menyalurlon bebon-beban loin dari struktur atos (superstructure) ke dolom tonah pondasidergan nembuof lubong bor bulot sanpai kedolornon terientukemudion mengisirryo dengon beton/ beton barfulong

Pondosi jenis ini dignrnokon jiko beban-beban dori struktur ofos cukupbesor, sehingga diperlukon diatnater pondasi yong lebih besardibonding pondasi ticng. Dampok pemoltongon pondosi bor padolingkungon sekitor lebih baik dibonding pondosi ticng koreno dilokukonionpo getaran..liocom-nocon Podosi borrc pile1. Berdasarkan kondisi dinding bor : (s1961 casing. tanpa cosing2. Berdosarkon bentuk dossr : samo seponjang bore pile, membesar.

Sipil ltenas 206 -

Page 15

PONDAST KAISON / CAI5SON Fq/NDATIONPondqsi koison/caisson foundotion odaloh suotu jenis pondosi dolomyong berfungsi menstronster/ memitfiahkan/menyolurkon bebqn-bebon loin dori struktur otos (supersfrtrctune) ke dalam tonah pondosidengan mengeluorkon tonah golion dori doscr struktur bulot yangterbuct dori beton bertulong sehinggo struktur bulot tqrsebut dopotterbensm ke dolarn tonoh kareno berotnyo sendiri hinggo nencopaikedalamon ycng dikehendoki, kemudion mengisi ruargbulot tersebut dengon posir atou oir.

Pondosi jenis ini digunokan jiko bebon-bebon dcribesor keoroh vertikol otcu horizontol, sehinggopondcsi yong lebor.

lllocon-mocon Pondosi bore pilc1. l(oison terbuko2. Koison Tekonon.

Sipil ltenas 2006 -

Page 16

4

Pemokoion terucuk, popon koyu. lemboran geofexiile, balok koyu,posir, grovel don boulder untuk meningkotkon dcyo dukung diatostonoh gcmbut atou lumpur. Contoh : pondosi untuk jolon kerja,jclcn rrya, jolon kereto opi atou landosan pesowat terbong.

tlAemberi lembaran onyonon banbu, geotextile, lapison posir,lapisan grovel/batu, rnemberi fosilitos droinase untukmeningkatkon dcyo dukurg don mengurangi penurunon sehinggraolai berot dopot beroperosi qtau untuk lolu lintos jalan roya

Cutoft wall, mengganti tanah porous/pervious dengron beton.melolui penboran. Contoh : perbcikon tonoh pondosi untukbendungon ogor rembeson yong melolui pondosi rneqiodiberkurang.

Sipil ltenas 2006 -

Page 19

I,IACAI,I.fiIACAIA ASAL BEBAN YANE DITERIfiIASTRUKTUR PONDASI

1. Berat sandiri struktur pondosi?.&dutg3. Bangunon oir (bendungon, bendung, saluran. dll)4. Jembaton/ jolan5. Pipa6. Aianoro7. Tangki8. ttiesin9. Dsb.

I,IACAflI-IIIACAIA BENTUK BEBAN YAhI6 DITERI,UASTRUKTUR PC'NDASI

1. Terpusot rA. VertikolB.lrliringC. Horizontol

2. f,ierota :A. Vertikol : lingkoron, segienpot, tropesiumB. Miring : segitigo. troPesiumC. Horizoniol : segitigu, tropesium

Sipillbn6 2N6 -

Page 20

6

IiACAIA-IIiACAI'T PO$ST EEBAN/RES{.'LTAN BEBAN PADASTRUKTUR PC'NDASI

1. Centris2. Berjcrok terhadop sumbu x3. Berjorok ferhodop sumbu y4. Berjorok terhadop sumbu x don y.

Sipil llen6 2006 -

Page 21

Sebutan FOUNDATION EMINEER (Ahli Pondasi) diberikankepodo seseorong yang telah nergenyom pendidikon forrnol dibidong geoteknik (mekoniko tonoh, gealogi, rekoyoso pondosi)don rekoyoso struktur (anolysis, perenconoon beton bertulang,bojo don kcyu) don felah mengikuti berbogoi nocom pelotihon,kursus, konferensi, seminar don feloh berpergoloman cukupdolonr pergombilan keputuson-keputuson berkoiton dengonperencarunn don pelcksonoon pondosi.

Tigo prinsip utamo yorg mininol horus dipenuhi dolonperenconoon pondosi :

1. Anon2. Ekonomis3. Proktis (dopqt diloksonokon derEon menggunckon bohon,

tenogo don peraloton ycng odo).

Sipil ltenas 2006 -

Page 22

7

Duo hol pnting yong menjodi pertimbangon utoma dolomperencorunn pondasi berkoiton dengon geoteknik yoitu :

1. Strength2. Deformosi

Seloin sfrergth don deformotion sebogai faktor yong meqiodi pertinbongonutomo, beberopa fEktor dibowoh ini jugo horus dipertinbonkon :

1. Kedolomon pondosi harus cukup dolom untuk menghindori erosi,pertumbuhan perakoron tonomon don pengoruh pengrgnlion pondasibangunon disebeloh, serto pergeseron.

2. Yeberadmn expons ive so i l.3. Foktor kearnonon ferhodap gulirg, gese?, don upliff (flototion)4. Aman terhadcp korosi don kemunduron mutu bahon.5. Sistem pondasi memungkinkon untuk menerimo bebon tambohan dengon

odonyo perubohon lopongon otou geometri konsiruksi don perubohonstruktur otas.

6. Pondosi dopot dibongun menggunokon sumber nateriol,peraloton don orang yang cdo.

7. Perenconoan pondosi diusahakon ogor dopat memenuhistondor lingkungon yong berloku.

Sipil ltenas 2006 -

Page 23

Dolan perenconoon pondosi umumnys diperlukon longkoh-hngkohsebogoi berikut;

l. Evaluasi terhodap lokosi dan posisi bebon.2. Pemeriksoon phisik lcpongon neliputi ospek geologi don bukfi-bukti \

yorg mungkin berpotensi untuk menimbulkon rnosoloh di kemudion hori.3. Penefapon progrom inv*ligosi/prryelidilon lcporgan tndupun pengujion

laborotoriun.4. lllenentukan porotneter tonah/bafu untuk perenconoan ydng diperlukon

berdosorkan dctc uji yang terintegrusi, mengikuti coro-coro ilmiah donerginecrirg judgmant. Dolom longkoh ini mungkin diperlukon analysismenggunokon computer otou nElokukan perbondingan dengcn dota-dotoyang direkomendasikan oleh literotura-literof ur otou Konsulton Geofeknikloinrryo.

5. Perenconson pondosi nenggunokan porometer-porotnefer dori lcngkoh no.4.

Sipilltene 2ffi6 -

P4e 24

I

Sifot-sifot phisik don mEkonik dori tonoh otau botu yong umum digunokon \untuk onalysis dan perencanoon pondosi odoloh tetapi tidok terbatos podo :

Porunetcr tomh atou botu unfuk Per.ctrcomcn Strukfur Pondosi

1. Strength Poromefersa. Siress-strqin |ttodulus, Es.b. Sheor liodulus,6c. Poisson rotio. pd. Interrul friction orEle,Oe. Soilcohesion, c

2. Compressibility Index ond rote of SettlementCompression Tndex, Cc

3. Gravimetric-volutnetric dotoa. Unii weight,yb. Specific Arovify, 6s

Void rotio, ePorosity, nWoter content, wLig$id Linit (LL), Plostic Limat (PL), dan Plosticiiy Index (PI)

Sipil llenas 20{F -

Page 25

Sfondords Test untuk filcmpadah Palunetcr Percrrconaan :

1. sNI (Standcr l&sional fndonesio)2. ASTI (Americon Society for Testirg ond ltltoteriols)3. BS (Bnitish Stondord)4. AASI{TO (Americon Associotion5. JIS (Jopon fndustrial Stcndcrd)6. AS (Austrolion Stondard), dll

Jsnis Tcst (PcrEuJian) uffirk ilsmpqloleh Ponornctcr Pcrcnconoor :L Peryqjion Laparyon:

o" Tst pit (pocket penstroncfer. rrune shcor)b. Rigid Phte l,ooditg (l5Ttl D 4394)c. Ducth Cone Panetrotion (DCF) Test (2 ton. 1O lon, 20 ton).d. Californio Bcoring Rotio (CBR) Tart (ASTlrl De. Stordord Perutmton Teri (sPT)f. Tesf itcrhod for Bcariqg Capocity of Soil for Static l,ood on Spneod Footing ( ASTlrt

119f)9. Test tliethod for Density of Soil in Phcc by Sond Corc licthod (ASTA'I b 1556).h. Test Alpthod for Pilcs Urder Stqfic Axiol Compressiw Lood (ASTtl D 1143)i. ltlstfiod of Tceting Piles Urder Ldterul todds (ASTrti D 3910)

of Testirg Xndividuol Piles Urder Sfaiic Lood Terih Lood (ASTI D 3689)

Sipilltenas 2@6 -

Page 26

I

2. Paqqiion Loborotorim :2.1. Ir&x T"st

o. Wotcr conncnt, w (ASTtll D 22!6)b. eru&crg lturib,ll, f'L. Pf (AsTlrt D 431E)c. Spedfic gnodty,or(AsTlrl DE {)d. Sicrc onolysie ond hrydronctcr, gradalion (AST,ti D,122, 4e21, ll40)e. Dcnsiiy, I {ASTttif. Srcllitg, %(ASTJf, 04546)

?.2 TFhxiqlo" Kodisi tJU :c.o(ASTAtlD2850)b. (onfsiA/ :C,d(ASTil D475nc. Koffligi CD : C,d

2.3 Dircct Shec : c,0 (ASTiI D 3080)2.4 Unconfincd compnsssion tcst. qu (ASI$ D e66)2.5 Rclcliw Dcneily, Dr2.6 Coruolidclion, Cc.Pc, C! (ASTlt D 2435)2.7 Peflwtuilit1, k (r{5Tlrl D?.E Conrpcciion, y 1*, OlilC39 Cclifornio Bcoring Raiio (49R). %

$iSilltenas AX)6 -

P4e 27

REFERENCE BOOKX) Pruncfpfe af Forymda#on fi.ngineeriffSr

Perugarang: Braje M" Eas23 Fsundatisn Ama/ysis & Desrgn

Fengarans: Jsseph Scwles3) trelqnik Fondasi

PengarasTs: Dr. ln $uhardjitoPradctc

4) tutelqanika Tanah dan Teknik PoHditor : Dn. lr. Suyono SosrodaKazutn Nakazawa

Sidl lbnas 2006 -

Page 28

10

SHALLOW FOUNDATIONSlntroductionsTwo main characteristics :1) The foundations have to be safe against overall

shear failure in the soil that supports them.2) The foundations cannot undergo excessive

displacement or settlement

The load per unit area of the foundations at whichshear failure in soil occurs is calledthe ultimate bearing capacity.

Sipil llenas 2007 -

Page 2

SHALLOW FOUNDATIONSUltimate Bearing CapacityGeneral concepts:1) Astrip foundation with a width of B resting on the surface of

a dense sand or stificohesive soil.

The foad per unit are, gu,ls usually refened to as theuftimate bearing capacity of the foundation. When suchsudden failure in soil takes place, it is calledgenenl shearfallure.

E# r-..-'*dartf a toad graduauy applied to =@ [==tthe foundations, settlement \ZXy L/willincrease. rn -H + /At a certain point

- when the load per unit are equals qu

- a

sudden failure in the soil supporting the foundation will takeplace, and the failure surface in the surface in the soilwill extendto the ground surface.

fii$llluus 2t07-Pry 3

SHALLOW FOUNDATIONSUltimate Bearing Capacity2) lf the foundation under consideration rests on sand or clayey

soil of medium compaction,an increase in the loadfoundation willalso beaccompanied by an increasein settlement.

The failure surface in the soil will gr:adually extend outward fromthe foundation. When the load per unit area on the foundationequal qun,, movement of the foundation will be accompanied bysudden jerks.

Aconsiderable movementof the foundation is thenrequired for the failure surface in soil to extend to theground surface. The load per nit area atwhich thishappens isthe ultimate beaing capacity, qu.

SiSrillbna 2007-Page 1

en-

2

SHALLOW FOUNDATIONSUltimate Bearing Gapacity

Beyond that point, an increase in load will accompanied by alarge increase in foundation settlement. The load per unit areaof the foundation, Qug, is refened to as the first failure load. Apeak value of g is not realized in this type of fiailure, which iscalled the localsfearfailure in soil.

3) lf the foundation supported by a fairly loose soil, the failuresurfiace in soilwill not extend to the ground surface.Beyond the ultimatefailure load, qu, theload-settlement plot willbe steep and practically

This type of failure in soil is called ihe punchingshearfailurc..

Sipilltenas 2007 -

P4e 5

SHALLOW FOUNDATIONSUltimate Bearing Capacity

Vesic (1973) proposed a relationship forthe mode of bearing capacity failure offoundations resting on sands.D"

- reiarive debily of r6rd

Or = dc#lr of fonnd*tloo rnclsrlrd f.rs lbt] grousd sorfuca'=&shete fi * dtlth of iourdrtioo

L = ltngtt of founrlati

SHALLOW FOUNDATIONSTerzaghi's Bearing Capacity Theory

Tezaghi (1943) was the first to present a comprehensive theory forthe evaluation of the ultimate bearing capaci$ of rough shallowfoundation.

Terzaghi suggested that for a continuous or strip foundation, thefailure surface in soilat ultimate load may be assumed: generalgflggg fgih rra

Bearing capacity failure in soil under a roughrigid continuous foundations. Sipillbna 2m7

- Page 2

l.-o-l

SHALLOW FOUNDATIONSTerzaghi's Bearing Gapacity TheoryThe failure zone under the foundation celn be separated into three

parts:1) The triangular mne ACD immediately under the foundation.2) The radialshearzones ADF and CDE, with the curves DEand

DF being arcs of a logarithmic spiral.3) Two triangular Rankine passive zones AFH and CEG.The angles CAD and ACD are assumed to be equal to the soilfriction angle f. With the replacement of the soil above the bottomof the ioundation by an equivalend surcharge q, the shearresistance of the soil along the fiailure surfaces G/ and HJ wasneglected.

fttl

Siipillbn6 2{n7 -

Page 3

SHALLOW FOUNDATIONSTerzaghi's Bearing Capacity TheoryUsing equilibrium analysis, Tezaghiexpressed the ultimate bearingcapacity in the form:

Assumed:genenlsharhllurc

wherc c'- oolsiooofrolt? = oahnci*htolsilc-t4

iV. ,V, lVr -

bcchgcspdcily fuctffi.hor nb d@diefidond ild srr fu*.lirlrdtt of dF n$l ftidinaqh#

B = widthldiameter of foundation. wt'sre.

n'-*{ffi -']= *'ot+-'|) iv.=ffiffi

"-i{#'-r}r*o'tr(, - paslvc pmtsurc EocfficiEol

Stpil lbo6 2007 -

Page 4

2

SHALLOW FOUNDATIONSTerzaghi's Bearing Capacity Theory

r.i,.f,,t. t.Tezaghi's bearingcapacity factor:

0I3,t567&

lot1Et3l4t,l6l,l8l92011a,3Ia

J.?t lfit 01il 26 lLE t{zt 9.846.q, Ll 00t n 2ll* ts.s llial6J0 La 004 a8 x.*t tl$l lL?le6 l.$ d(5 8 3{-14 lr.S lilr6,g, t#l tuo 30 !r.16 1r-4rt 19,13?34 IJ'l O.l4 31 4o,4I 5za 2ai51"?t r.El 0?0 3a t4ia 28,52 &,tI&rJ r'fll lun 3: S00 JA,S il.r4[J0 2.?l r]15

-1r ad4 36.9] ,&0{olt{ 1{4 0.'l* lt tt75 {l.d{ {A4lg.fl adl ff6 * 65t ir?,l6 s.Jf1{lt6 efl 069 v ?l$r tLgl 6d27to?6 J.tg oEJ !8 ?7J0 6ri$ ?&6tili! tfg J.rx 3t 3ft? z16l {1,6lllt t&. |.t0

'10 9ti6 8lJ? tl53tl?J* ,Ltl lje {l ltSEI 9l.tS rintlli66 a.cg llll 4t 119.6? llB,7J t?1.9t1{.60 td5 218 ,ll l34J* lj!6.Jt} 2llj6r5-r2 6.0* zt9 4 r5rr5 14134 ?6l.j0l6J6 6.flr t'1't *5 lTZ.2l l?ats lail4t1# ?.{.t t^d4 d6 ls.a a4.l9 tr.lli*9: &26 4Jl r, 2l,t-1i r,lLfrl tlz.t{?.lt to?3 6,flr 49 ?9871

'4{.6 El,r!'a$ ttJo r,rs fll :r4?st 4lJ,u lo?!,etai.[t lzr2 &1{

fiifillbnas 2fl)7 -

P4e 5

SHALLOW FOUNDATIONSTerzaghi's Bearing Gapacity TheoryFor foundations that exhibit the local shear failure mode in soils,Terzaghi suggested the following modification:

A. = !"'.V: + qiri + hElvi {srripfourxt*tion}q'

- O*fi?ctfl {- d'Ji + &47AI9i {squrrt fomdu*m}c, * 0ff?cr,f! + 4/vi + &Svfttri (cirotlartounduiott)

N"', Nq'and Nr', the modified bearing capacity factors, can becalculated by using the bearing capacity equations (for N", No, and N'respectively) by replacing 0' by 0' = tan-1 (%tan l'1

Sit'illbn6 2007-Page6

3

SHALLOW FOUNDATIONSTerzaghins Bearing Capacity TheoryTezaghi's modifiedbearing capacityfactor:

&xt,{' r. ii0 t,zr llD 0ff1I $,$ lJn 0fi62 Al0 l-t4 ltfr.I 63D t&, 0jlr{ 6Jl 1"30 tr,tr'5 C?4 l-!D olrtrl6 6$t L,{t &lt}7 7&. t3' ol:8s ?37 t.?o 0.liI ?.?4 t& Dg|$ alE' t,94 0.24il &Ja e0 o3lt12 &63 zgt oJ6$ &!6 ljt ,0el. *il lJJ 0r*t5 9i? L?t oJtf6 roffi ttz otr?l? lo.fr x,t! t?6l8 l(}s 3J6 0,8e19 il*r6 3'fl t.88 lltr xrf, r,u2t lLTl iLlT IJJt2 ,zn 4.,.11 t.t!?3 ti.'t dta n44 t4.t4 5.4 $Ilt tdf,r

'fr 2J3

A,1a20lo3t3T3J3|ltfi$38{,lll41a*ltdt5{641.lft49JO

ttsr fiE1630 d.54t?.13 7.il1t8,{E 7fita99 *Jl?o$ 9.01:t,t6 s'lar2je r{utaaa lt5?2J,15 t175lt77 t5,9'28.5t tJ.!nto.{r l6,Ec3a5B r8-q63rt 30J0flt1 En.l0'$ ?5tt'Lltl ?ln6{?-t3 3t"}*fl.r7 tt.il5S?3 30.,1Sd(t9l 4&tt66.fr1 Sr]{itts,t5 5'*lStJl 6t.dt

lJD:JEtt9t164iilt4AtJJIfta1,a,nrs9,*1

10.stx?tr4.tll?:1t9.?t21508*:rt4036.{L,11.?0ag"Itfi,&?r.*58!7t

Si$llbnas 2(X)7 -

P4e 7

SHALLOW FOUNDATIONSFactor of Safety (FS)Calculating the gross allowable load bearing capaci$ of shallowfoundation requires the application of a factor of safety (FS) to thegross ultimate bearing capacity, or: {rq..

- Fg

The net ultimate bearing capacity is defined as the ultimatepressure per unit are of the foundation that can be supported by thesoil in excess of the pressure cause by the sunounding soil at thefoundation level,

wtcrc qraol - natultittutcl'EarfugcEPacityq'tDtSo,

,la -

ttr{dttll-B-

$ipillbn6 2007 -

Pqe 8

4

SHALLOW FOUNDATIONSTerzaghi's Bearing Gapacity TheoryExample #1Asquare foundation is 1.5 m x 1.5 m in plan. The soilsupportingthe foundation has a ftiction dngle 6'=26o, and c' = 15.2 KPa. Theunit weigh of soil, y, is 17.8 KN/m3. Determine the allowable grossload on the foundation with a factor of safety (FS) of a. Assumethat the depth of the foundation (D) is 1 meter and that generalshear failure oocurs in soil.

Answer:From table:

Sipil lbna 2007 -

Page 9

SHALLOW FOUNDATIONSTerzaghi's Bearing Capacity TheoryExample #2Repeat example #1, asssuming that local shear failure occurs inthe soil supporting the foundation.

Answer: f''ij*,ili#E$:i f.$,i

Sipillbn6 Zn7 -

Page 10

5

SHALLOW FOUNDATIONSModification of Bearing Gapacity Equations forWater Tablelf the water table is close to the foundation, some modification of the

form: s - cffcd"elurtt$F * G?,t &fu*,- r*)

bearing capacity equations will be necessary: -1

#*,trfuffi[itri1]ffi:-(t-

- rdua.d**do

The value of y in the last term of theequations has to be replaced by y'

n Gase ll: lf the water table is locatedthat0

SHALLOW FOUNDATIONSMeyerhof's Bearing CaPacity Theory

Meyerhof (1963) suggested the following form of the generalbearing capacity equation:

**-,a:al1r r+qfffi4.ftF;*∈rbF,irtWhere: r,'- ctlxsion

{ = elT*etivc itrc$s at lb$ krel of rbe bnttom of rhe foundation? - unit wcight ofsoild - wljth of louodilion {.= dierneter for a circular found*tioo)

1,"' fn, Ji, - duPc factorsf,,a, Fa1, F6 - tlcFth factors4r, Fr, 4t = bad inclinatkrn fnctore,il* ffr 4 = berrrlng,capacitY faaors

for the case of rectiangular foundation (0 < B/L < 1) andaccount the shearing resistiance along the failure surfacein soilabove the bottom the foundation.

Sipil lbnc 2007 -

Page 2

SHALLOW FOUNDATIONSlldeyerhcf's Bearing Capacity Tlreory

khe.op"11l...^-,,- -N. = (rYr - llcot$- !

'q*rnorr.*r- |Egustbtr (3.22)-(iri- rlran(t.id');ffi- t' * '*'(ut n f)'t-*n

I I oJ{a/l)I

r +0.?(8/t)la#{{s+dlz}I + trr(a/L)taB (45 + *'/?)

I + 42@r!B'I

I + 0.?{Prl8}latr(45 + O?}| + 0.1 (Dlrrf )bn(45 + d /3)

Sipil liene 2007 -

Page 3

2

SHALLOW FOUNDATIONSMeyerhofns Bearing Gapacity TheoryExample #l!A square foundation has to carry a grossallowable total mass of '15.290 kg. The depthof foundation is 0.7m. The load is inclined atan angle of 20o to vertical. Determine thewidth of the foundation, B. Use MeyerhofsBearing Capacity theory and a factor of safetyof 3.Answer: From table:

N" = 30.14, No = 18.40, Nr = 15.67

q = T Df = 18 * A.7 = 12.6 kN/m2

Fo" = F* = 1+0.1 (B/L) tan2 (45+6'nl

l*-a-'l

'

Pry5$pillbnas ZX)7-

C\(1)(t,(ErL

II\ooc\u,(sLc)P'd-6

ffi

ffi

lFoc.9+,J-ot-

. .l-,E .9,

8io(U.9(J?.-suL-bP;e

-f=F

o{-,co

yEio(u.ga+tcoEoEo+.Eo#toob-Jaol-(ECo*-,(sccJoq-aoa(Uo(ul-ooac

aCo

lI'*,

IE!tCIJolJ-T'oE(EoJ

-

-IUo

t-l-{rlgooo

UJ

azoIl-oz3oIL

=oJJ-

Ia

co

yoEcJ

ioge+t(uc

.9oFP-rtt t-yq

t-(ExE6 Feli '

=o>

aEA$

(f,(l)(5)(5(LI

l\oO6tq,(oGc):4a)

'!(5E(t

l+-oof(U

o-cF

.ctr{E

,qB Ft,Eb 3FRfi fl"YN: (l) (r.l,e'= : i(-e.-

= r-#3sg

gE E:Z6EaoE I oH H:=8 s I FE;E EEE FEE ggEfrFE#

-I-(--H I- ,tl68I g-

:F

=E 88

oa>=o+,cooooo-c{-,a

o()c(U*-,

.aEo-cF

aco

l-*,(U?tc=oIJ.EoT'(EoJ

-

ITEo

IIL.{rlco(,(JlU

H larilEJ

azoIl-oz3oIL

=oJJIIa

$(l)CDcto-

II\Oo(\lC"G'co-

.gCN

aiilmEc(Uo(\I

IJltJl{-oo=oo-c.r:,

co+,(trEcJo_

Ege gor( .=

g,H# EA EHEe 83 H bEEg EE E FETE Efi E EE'}sE q5 g bEPE

=9 E cEAi .p:S 3 EtE' *fs E.q E-c=F cA A:_ E I .!ggE {o.E qoJga O=

.EbEl A'. u os:3 gE$ fiFFE 8E .

fiEF*5EfiEftgFtuF ()-O (UF= $ F

ago

II*r,(EEg

IJoIJ.!toE(EoJ

II

GC)

IIt:*,go(,oUI

azoIFoz3oII

=oJJIIo

rr)(t)o,G'

TLI

t\ooC\actc"o=CL6

-=

t5s

ll -'j dlqr\.d IwH

.9,

=.a ESo-da=::-JJu' '(u !'c#lllqlu)\, .-- I-nLE[ b6$6ovEcC')ct5Co'=9r?-cUCaa'65-ocr)-+rGlEE(- +-,Fcuo?rO)-H6',EosE 3fti(UOF'/,+'bJo'.;=E.Efr- o9(uxt

*-, v0(E-vqFrF(Jooq-c -c -cFl-O

A(f) $ lo

-cg]c,'=

-co6--coootsco'FEEco(s6-cErlr,o).oCl-o>OE

Y yo().oolr-iE O-

!rOf,)q -cE

.qi.=; q =mm.= H L-

-F H SHEtu'' + ,EJm3 S sEgc .s $C $'= a -c (U=E F .ltu-O + O

-

+-,o t o'= oE +l Ecc=

L' =.9 o

.=

=iYCr-=

I R Oot,\lrFY# FESN

aCo

II+,(UT'c

IJoIJ.T'oErtroJ

II (E(,

IIL*,trooo

IJJ

azoIl-oz3oIL

=oJJIIa

(ooo,(Eo-

It\oo(\I(ttCUc(l)=o-6

*:aI

zIJJIIFoz

T#i-r,a

I=c:f,

-=E bc^'o-a .e,;e-vt6.?;rooX

.- tvLAF +, tJt-Al-L.!/(1)ooutu H tEEE 6 EE=o: ="gE=6L,' dt rF\tS 3 oE*o:fh -o E;5o =: EE iiF E; E; 9

= o=oo) ofi:PgE E

aco

II{rlG'Ec:IoIJ.EoT'(troJ

-

I (tro

IIL+,coooIJI

azoIl-ozfoIL

=oJJta

Fl_I

-\4tlarfiV

-FioH-EI l ufi h.*., a

5-rgat&E9,--T*F

'\'- S?6tCi a>t {- CD(t'(LIt\oo(\Ia(uc(l)=CLcn

@

To

tE

rrl

ago

TI*,(EEg

IJoITEoT'(EoJ

II

GoIIl-*r,trooC)lU

azorFoz3oIJ.

=oJJI.LCN

T{Fg

e+ .a=\ o)o6, ll .= lcE3^EE={^g EA-r+7O-Y .rF (U|otro-c.-''2;

.& 3,rcE a.=-c.gr o I _bsE$gS EE F gF

.s frEfiEE gfi FT*SE E

SHALLOW FOUNDATIONSVertical Stress lncrease in A Soil MassStress Due ToA Concentrated Loadln 1885, Boussinesq developedthe mathematical relationships fordetermining the normaland shearstress at any point insidehomogeneus, elastic, andisotropic medium due to aconcentrated load located at thesurface.

Aqs

Sipil lten6 2007 -

Page 2

SHALLOW FOUNDATIONSVertical Stress lncrease in A Soil MassStress Due To A Gircularly Loaded AreaBoussinesq's equation can also be usd todetermine the verticalstress below the centreof a flexible circularly loaded area. Let theradius of the loaded areaBl2, and let qo be theuniformly distributed load per unit area.

( . fn f -'x

'(qidttdrl8s=)d0 "-[_" 1.";F(JT-"{'-F;ffi}

Sipillbne 2)07 -

Prue 3

SHALLOW FOUNDATIONSVertical Stress lncrease in A Soil MassStress Below A Rectangular AreaThe integration technique of Boussinesq's ;equation also allows the verticalstress atany point below the comer of a flexiblereciangular load area to be evaluated.

- t / zanVurt* ot'. t rtr {- lt3 t 2

, - trtlutru.._ tts{"r - G\r",, n: .,,rlr: + l.;;T;:l. lrnrfiiJ,FT \

=lirn'- --'a' + tf 4 I - Hr/rl

J-

Page 4

t I- arur.4Fi ,i + i mr + a'+ 2 I, = influcocl'fucttr r

-l -

,- .. ;-:--'--=-:-----;-:-- I4nLPf +rr+nrtr - I nr+n-+ I I.t{ ra''\,' ++++t+)J J

al+#+l

)h-eL

L

^o t!LLL

%_b

o,3/.s

AJC/."r

F- 13= t,f,a ---{'l

ig=o,,9ar

lal=q_-g --I

l

I

'--tI

I

*--g ------+

'= 0,1

fu"t n'rul? 3.rz (a) ,r*xn/F/+1w fle re %tE otr e%< o'r&-,va O

IP+6r t?s1

,

+ = o.B,f ,^) Lr - p,Ar)(f1 = /.2ff ,,L4 s o.2/ Lz

' (a.u)6t"$) = 0,3rr ry .LV*.*Eer;vF ArzA= ht = $ (t,,*/>). B.= $ (/.2F* 0.vr)(.rs r/g3 hz6-pVg-q7'VE ten/nV

= L'- L, on.L, (ari"11sysg r tt,eete.), fr,L' = Lt c /. z/z ,,.1Bt. + =. ,4t_=0.916^1// /.zVz 'vv

utE fifF erilE*t BehlL,'^tr u*rt+ry otru,rnba ffia7 oaq+zzB2Fo :

lla" eNeEs trq.E; * ?, Nql"ho E,; * t r B Nt&5^nq: = c AtsFsE r.atr; * q,

^lq 4, fi,an; * + / ts' Nl5.*n rr;q * Df,

^ tr = o.V xrP =tz.A Lyn,

ru^4 7w3t 3..2 , a.e*d$ Mff frl-?n( [h,?nc Wie /l/])(*W+t4- D+t / f+trf BD fVA d.J7, ; Ne= 3"0.t/*r,

= tg,y

NA = 2^.Yfort c=o, xr' = I NaftrGai,z + ty ^B'n/ *" 3"U#0n 77faL Z.f r l4t6l ns7rt/ r Hv) ir*lirt+np^t fVt-fu< ,@va^tDDf?e uE Ud+ n- Ltrr i+tr nts '

Y= of =o'?f

4, = , n fi "?",/ a /* ('E) taq 3oo = t'vzY4*. t*z@f (,-thP)' F

c t + a*a,, gor(t-sn 3o')" (.X),^r f:Kffirt)iT A r).

= lr ( z +u 3 o' [0.2r)( o' t/6 l)s t r (r. n ) p.zr) (0. ?t /),= / f 0./3f= /. tgr.

rlrs /* o^r ( #l= /*ov ('#')'o?o('fYa

= 't

4r' s (, uqQrfflTfq;+ * trt' Ni htFnF, *qi tfi= t,t&*up /- o'

= 8r. 6)(rs-:')(,. v>vxr nr)() + t (p) p"t tt1 122.r )0r6x,y,le tT/. 13 ..LN&L

l*ilt-Fl

Q,rq = Cr' * e+wrtiuE ,ntfr or maa+rio*ts ,ro/-rz x tA' *L')= o/.%x (t.?gAxtzTz)s 6oY.7y.lrN.

3.5 General Eearing Capacity quation

Table 3.2 Eearing Capacity Factors'

C N. N. N, . N.lN. tan {

133.88 134.98 27r-76 l.0l l.0O152.10 158.51 310-35 1.04 l.O{t77.64 187.21 403.67 1.08 1.07t99.26 222-ft 496.01 t.tz l.l I229-91 265-51 613.16 r.l5 t.l5266.a9 319-07 762.89 1.20 l.l9

131

o 5.14 1.00 _

0.00 0.20 0.00I 5.38 l.O9 0.07 0.20 0.022 5.61 t.20 v 0.t5 o.2t 0.033 5.90 r.3l O.24 0.22 0.054 6.19 t.43 0.34 0.23 0.075 6.49 1.5? a 0.45 0.24 0.O9

. 6 6.81 t.72 0.57 0.25 0.1r7 7.t6 1.88 , 0.71 0.26 0.t2

..:f,: gr:: 7.53 2.06+,:'...9.96.:'r, O..27 0.149 752 2-25 1.03 O.29 0rt6r0 8.35 2-47 r.22 0.30 0.18ll 8.8O 2.71 1.,14 0.31 0.19t2 9-28 2.97 1.69 0.32 0.2113 9.81 3.26 1.97 0.73 0.2114 10.37 3.59 2.29 0.35 0.2515 10.98 3-94, 2.6s 0.36 0.2716 11.63 4.34'': 3.06 O.37 0.29t7 t2.34 4.77 3.53 0.39 0.31l8 13.10 5-26 4-O7 0.40 0.3219 t3-93 5-80 4.68 0.42 0.y20 14.83 6.40 5.39 0.43 0.362t t5-a2 7.O7 6.2C 0.{5 0.3822 16.88 7 -82 1.ti 0.,16 0.,()2t 18.05 8.66 8.20 0.48 0.4224 t9.32 9.60 9-44 0.50 0.4525 2n.72 10.66 10.88 0.51 O.4726 22-25 I r.85 t2.54 0.53 0.4927 23.94 t3.20 14.47 0.55 0.5128 25.80 14.72 t6.72 0.57 0.53a 27.86 t6.44 19.34 0.59 0.55

I 30 30.14 18.40 22.& I 0.61 0.580.63 0.60

32 1s.49 23-t8 n-22 0.65 0.6233 38.64 26.09 35.19 0.68 0.6534 42.t6 29.44 41.06 0.70 0.6735 46-12 33-30 48.03 0.72 0.?036 50.59 17.75 56.31 0_75 0.7337 55.63 42-92 66.19 0.TI 4.7538 6r-35 48.93 78.03 0.80 0.?839 67-87 55.96 92-25 0.82 0.81.l{) 75.3t &.20 l09.4l 0.85 0.8441 83.86 73-90 130.22 0.88 0.8742 93.7t 85-38 155.55 0.91 0.9043 l05.ll 99n2 186.54. 0.94 0.9344 I r8.3? I15.3t 224.& O.97 0.97

A.ftcr Vcic (1973)

*@qq*+::,:n

w'133 ^3.5 General Bearing Capacity EquationTable 3.4 Shape. Depth. and lnclination Factors Recommended for-Usg

Factor Rclationship Sourcc

I

I

I

I

Shafrc'

foundation (L >Dcpth! Condition (a)

kFa:l+0.4;I na

,\r),,\ \ 1-

-

sin drr AB

aN-,. F,,: I +;.#

L /Y..:

.By' F,,: t + Ttzl:. 0

BV Fn= I -0.4;

whcrc L : lcogrh of the

\F,r=l+2tan0'(l\t Fl:l

Dc Bccr (19?0)

Hanscn (1970)

Condition(b):D1lB>l .g:.:-. ,,,..F,t: | + (0.4) tan-' (&)

"'-' Fnt: t:+ 2 t s'0(1' - '611'"t1"6.t.(2)Fr.: I

ill

I

l

Inclination,"5)=('-#)'o.','-

(' - i)' :whcrc p

-

inclirutiooof tbc load on thcfoundation with rcspcctro the vcrtical

Mcycrhof (1963); Hannaand Mcycrhof (t981)

itvl'* ti nFtinn5t

For undrained toading conditions (d :0 concept) in clayey soils' thegeneral load-bearing capacity cquation fEq. (3.t6)] takes the form (verticalload)

' Thcsc sbepc factor: erc copiricel rchtioos b$Gd oo Grtedsirc l'bo-etory t6t3r Tbc fector ta- t tDtl8; is ia r.dians

g" = cN, F", Fr, + q

Hcnce, the ner ultimate bearing capacity is cqual to (vertical load)

{nc(,t - q" -

q: cN. Fo Fra

\.(3.2r)

()-22,

eD^)mil filrr- IMp* n n67UtE /Jfutil. 4 fuu^rbrfrAv /. f 4 x I t'4 tr tOc47P rf lr b9"7tl(t.g)of /n /ryA eury.4.Otrchf t+yt'/? rL\e+&V rrr*o#IV(t+1 0p / n ,,l*4tttw, Wkl W Annlbt 0F W ftw&ilnt .eitmt !

- fvR nf a'ry Ufyn :Unttn,+1 ttrb {lf24 CrWtlffi(tNtr wr)fW

-frtL B2mq ebT W* :Qn b4oiu*V tffire sagwffi

?dr wtftlfr

s /20 -LU/rz: /6.' fu/r ts lB -l,a/4 zs /6,2 .!LN/k, L

BOTTD,',1 L,IT*CLhY

tz = t6. z Ltl/rzCupT' VE jntpt);0 ,

lilzztaaa'ta flE iraotr klt\A*lttf tAtl f?A 7/rtAea:A+nop d4 4ftaryA 0F tffi'a 0F ? ,

t\\B'wp ut{e4

SoLun'lil lqivd : qtt)= /20 i-{/rz

tlxl W-&t4 '

cL'/lBxt y,=, tl.8 Ltt/^t

%0\z lLo 4N/*z/t,> -' b

i Cq[4= Yg lcV/^z ,

> ?"tr= [rc'4(iler,(r-) 't-q -I\t"'+!)* y, Ds- .< ptc'. r{*))ottile+Vt Dy

2,

U4IAE B:/tvrL

-- Ir4

Df=,'t/ olrotNc

- g,ty frun 77rsL I.z tutc / = o)

t,*/6,8ttr/ntruq n?ecr s.t9r ftA ffi = #0, o.?r rwu4ae 0F tO,= 42,Sbt fo = p-g)fi>il = IoB tcn/^, ,tor |rr=[*L'ztin^&, Ne+ (,. *)(M1+ /, b.t

- Zn.613& + tl.B = 6rC.y -l.N/v,z

Now Al&k I%,^' tr *P''>$[ ar,) "' + N, bt

= 0 * p,r\C{rfA*y" q t gth8/r\= 69, + t(-! = 7/r'P^ Lu/nu

$, fru = 6 rr. y t*N/r, tffr,!; LFo or rw urar c*teru+Ez

nr,u' k = u+'=tbY'14'/5'totm- irLloh/utttr Lo+o [Qrtt) 't

&+,1\ ( A) = (16o'r)(r)(r'r) - zvt 'r 4N '