FINITE ELEMENT ANALYSIS OF REASONABLE FOUNDATION FOR SUPPORTING SILO’S TOWER | Nurdin | SMARTek 895 2863 1 PB

FINITE ELEMENT ANALYSIS OF REASONABLE FOUNDATION FOR SUPPORTING SILO’S TOWER

Sukima n Nurdin*

Abstrac t

The limita tio n o f so il d a ta d ue to p o o r so il inve stig a tio n p ro c e ss is a c o mmo n p ro b le m in c ivil e ng ine e ring p ro je c t. The finite e le me nt me tho d wa s use d to a na lyse the c o mp a tib ility o f fo und a tio n to sup p o rt silo s in Live rp o o l Do c ks. Bo th sha llo w fo und a tio n a nd p ile fo und a tio n we re c o nside re d. The re sults o f the a na lyse s a re p re se nte d b y c o mp a ring a na lytic a l a nd nume ric a l so lutio n. Pa ra me tric stud y wa s c o nside re d fo r e a c h c a se . The re a re d iffe re nt re sults fo r two typ e s o f sha llo w fo und a tio n tha t ha d b e e n c o nsid e re d. Strip fo unda tio n se e me d mo re re lia b le tha n p a d fo unda tio n, while Pile fo unda tio n c o nside re d to b e first c ho ic e due to the sa tisfa c to ry c o nd itio n fo r a ll fa c to rs.

Ke y words : Finite Ele me nt, Silo , sha llo w a nd p ile Fo und a tio n.

Abstrak

Ke te rb a ta sa n d a ta ta na h ka re na tid a k d ila kuka nnya inve stig a si ta na h se c a ra m e nye luruh se b e lum p ro se s d e sig n d a n ko nstruksi a d a la h p ro b le m ya ng um um ya ng te rja d i p a d a p ro ye k-p ro ye k te knik sik-p il. Me to d e e le m e nt hing g a a d a la h d ik-p a ka i untuk m e ng a na lisa je nis k-p o nd a si ya ng d a p a t m e nd ukung d a ri silo s d i Pe la b uha n live rp o l. Po nd a si d a ng ka l m a up un p o nd a si tia ng ke d ua nya d ip e rtim b a ng ka n untuk d ig una ka n. Ana lisa te rse b ut m e m b a nd ing ka n m e to d e num e ric m a up un a na litik. Ha sil d a ri a na lysa te rse b ut m e m p e rliha tka n ha sil ya ng b e rb e d a d a ri d ua tip e p o nd a si d a ng ka l. Po nd a si strip m e m b e rika n nila i ya ng le b ih o p tim a l d a rip a d a fo nd a si p a d . Se m e nta ra p o nd a si tia ng m e nja d i p iliha n p e rta m a ka re na ke la ya ka n d a ri se m ua fa c to r ya ng d itinja u.

Kata Kunci : Ele m e n Hing g a , Silo s, Po nd a si tia ng d a n p o nd a si d a ng ka l

1. Background

Te n to we r silo s a re use d to sto re c o m b ine d we ig ht o f a p p ro xim a te ly 3000 to nne s o f lo a d . To we r silo s we re e re c te d a t q ua ysid e o f Ale xa nd ra d o c ks in Live rp o o l.

O ve r the ye a rs silo b uild e rs ha ve im p ro ve d the d e sig n a nd c o nstruc tio n o f the a b o ve -g ro und p o rtio n o f silo s, in c o ntra st, ve ry little ha s b e e n d o ne to imp ro ve the fo und a tio n. To we rs ha ve g e ne ra lly b e e n e re c te d o n fo und a tio ns c o nstruc te d b y Fug ro Limite d . Who ha ve the ne c e ssa ry te c hno lo g y fo r

a d e q ua te d e sig n a nd c o nstruc te d . The p ra c tic e wa s re a so na b ly suc c e ssful whe n silo s we re d e ve lo p e d . As b ig g e r silo s we re e re c te d , ho we ve r, a nd the a p p lie d fo und a tio n p re ssure s a p p ro a c he d the b e a ring c a p a c ity o f the so ils, m a ny struc ture s se ttle d c o nsid e ra b ly, so m e tilte d , a nd so m e o ve rturne d c o m p le te ly. This d ig e st o utline s the p ro b le m a nd ind ic a te s the ne e d fo r a so il inve stig a tio n to d e te rmine the a llo wa b le b e a ring c a p a c ity a nd c o m p re ssib ility o f the so il a nd thus e na b le p ro p e r fo und a tio n d e sig n.

1.1 The p ro b le m

Ma ny to we r silo s c o nstruc te d o n c la y so ils ha ve ring -sha p e d c o nc re te fo und a tio ns. To re d uc e c o sts, c o nc re te flo o rs a re se ld o m p ro vid e d . Whe n the silo s a re d e ve lo p e d fo r a ny p urp o se s, p a rt o f the lo a d is tra nsm itte d thro ug h the c ylind ric a l wa lls to the fo o ting s a nd the re m a ind e r is c a rrie d d ire c tly b y the so il insid e the ring fo und a tio n. The und e rlying c la ys c o m p re ss ve rtic a lly und e r the we ig ht o f the lo a d e d struc ture in suc h a wa y tha t the a p p lie d lo a d s a re d istrib ute d unifo rmly to the so il o ve r the who le a re a e nc lo se d b y the c irc ula r fo und a tio n. This unifo rm p re ssure is d istrib ute d to the fo und a tio n so il in the fo rm o f a p re ssure b ulb ; its size a nd sha p e , d e te rmine d b y e la stic the o ry, a re re la te d d ire c tly to the d ia m e te r o f the lo a d e d a re a a s sho wn in Fig ure 1.1. He re , two fo o ting s o f d iffe re nt size

c a rry the sa m e unifo rm lo a d , b ut the p re ssure b ulb und e r the la rg e r fo und a tio n is m uc h la rg e r a nd d e e p e r. In e a c h c a se the m a xim um ve rtic a l p re ssure o c c urs im m e d ia te ly b e lo w the fo o ting a nd d im inishe s to 10 p e r c e nt o f this va lue a t a d e p th e q ua l to twic e the d ia m e te r o f the fo und a tio n. If the a p p lie d stre sse s within the b ulb d o no t e xc e e d the she a r stre ng th o f the so il the struc ture will b e sta b le .

No n-unifo rm p la c e m e nt o f silo s d uring lo a d ing ha s c a use d m a ny p ro b le m s. Whe n the lo a d fro m the we ig ht o f the silo s a nd the live lo a d is o ff c e ntre the p re ssure b ulb will b e d isto rte d , a s sho wn in Fig ure 1.2(a ). Stro ng wind s a c ting o n a ta ll silo c a n p ro d uc e the sa m e e ffe c t. The lo c a l o ve rstre ssing o f the fo und a tio n so il m a y c a use tilting , a nd unle ss the p ro b le m is re m e d ie d it ma y inc re a se with tim e until the silo o ve rturns.

Fig ure 2. No n-unifo rm a nd o ve rla p p ing p re ssure b ulb s.

Pre ssure b ulb s will o ve rla p , a s sho wn in Fig ure 1.2(b ), if two o r m o re silo s a re c o nstruc te d to o c lo se to e a c h o the r. Be c a use p re ssure s a re a d d itive , the re sulting p re ssure b ulb will b e m uc h la rg e r a nd will e xte nd to g re a te r d e p ths. The so il in the o ve rla p zo ne will b e sub je c te d to hig he r stre sse s a nd the fo und a tio ns o ve r this re g io n will se ttle m o re , c a using the silo s to tilt to wa rd s e a c h o the r.

Mo st fo und a tio n fa ilure s in c la y so ils o c c ur whe n a silo is q uic kly lo a d e d fo r the first tim e . As filling p ro c e e d s, the lo a d s a re a p p lie d to the so il ske le to n a nd to the p o re wa te r c o nta ine d within the vo id s o f the c la y. Pre ssure s g e ne ra te d in the p o re wa te r te nd to re d uc e the fric tio n b e twe e n so il p a rtic le s a nd he nc e d e c re a se the she a r stre ng th o f the so il. If, a t the e nd o f lo a d ing , the a va ila b le she a r stre ng th is g re a te r tha n the a p p lie d she a r stre sse s, the struc ture will b e sta b le . With tim e the e xc e ss p o re wa te r p re ssure s will d issip a te , the so ils will c o nso lid a te a nd g a in stre ng th, a nd the struc ture will b e sta b le fo r sub se q ue nt lo a d ing s.

In silo s witho ut flo o rs, sila g e juic e s no rm a lly se e p into the und e rlying so il. Po re p re ssure s a re inc re a se d e ve n m o re , c a using a furthe r d e c re a se in the she a r stre ng th o f the so il. The fo o ting s m a y a lso b e c o m e und e rm ine d whe n the liq uid flo w thro ug h the so il und e r hyd ra ulic p re ssure . Eithe r o r b o th o f the se a c tio ns c a n trig g e r a b e a ring c a p a c ity fa ilure .

1.2 Site Inve stig a tio ns

Re lia b le a nd e ffe c tive site inve stig a tio n is wid e ly a p p re c ia te d in c ivil e ng ine e ring a nd b uild ing p ro je c t, the g ro und c o nd itio n is usua lly g ive n the la rg e st risk e le m e nt o f fina nc ia l a nd te c hnic a l a sp e c t. Alm o st e xc lusive ly, the sc o p e o f g e o te c hnic a l inve stig a tio n is g o ve rne d b y wha t is ne e d e d to c ha ra c te ristic the sub surfa c e c o nd itio n a p p ro p ria te ly b y ho w m uc h the c lie nt a nd p ro je c t m a na g e r a re willing to sp e nd (M.B. Ja ksa e t a ll,2005)

Be a ring c a p a c ity a nd ve rtic a l se ttle m e nt a re d ire c tly re la te d to the e ng ine e ring p ro p e rtie s o f the so il a t a site , so tha t a so il inve stig a tio n is re q uire d to p ro vid e info rm a tio n o n so il p ro file , lo c a tio n o f the g ro und wa te r ta b le , ind e x p ro p e rtie s, she a r stre ng th a nd c o m p re ssib ility.

The site inve stig a tio n wa s c a rrie d o ut a lo ng Ale xa nd ra d o c ks b y Fug ro Limite d . Ho we ve r, the site inve stig a tio n la c ke d d a ta to e nsure a d e sig n o f p ro p e r fo und a tio n to sup p o rt the silo s. So m e b o re ho le s we re d rille d a ro und the site .

1.3 Te c hnic a l Asp e c ts o f Silo Fo und a tio n

Eve ry o wne r sho uld insist o n a n a d e q ua te fo und a tio n fo r his silo a s p ro p o se d b y C a na d ia n Build ing Dig e st (C BD 80, C BD 81). The fo llo wing p o ints sho uld b e c o nsid e re d to e nsure a sta b le struc ture :

a . Re info rc e d Fo o ting s

A ring fo und a tio n is sub je c t to b e nd ing stre sse s fro m ve rtic a l wa ll lo a d s, so il p re ssure s, a nd the c irc um fe re ntia l lo a d s tha t e xist in the wa lls a t the b a se o f the silo . As c o nc re te ha s a lo w te nsile stre ng th, the fo und a tio n sho uld b e re info rc e d with ste e l to re sist suc h b e nd ing m o m e nts a nd te nsile stre sse s. If the fo und a tio n sho uld c ra c k b e c a use o f insuffic ie nt re info rc e m e nt, the m o no lithic b e ha vio ur o f the ring fo und a tio n will b e d e stro ye d a nd its a b ility to sup p o rt the sup e rstruc ture a d e q ua te ly will b e re d uc e d .

b . C o nc re te Fo und a tio n

It is m o st imp o rta nt to use g o o d q ua lity c o nc re te in a we ll p re p a re d e xc a va tio n in whic h the sid e s a re

ne a tly trimm e d a nd the flo o r c le a ne d o f a ll d isturb e d so il. In g ra nula r so ils o r so ils c o nta ining b o uld e rs, fo rm wo rk m a y b e ne c e ssa ry. The c o nc re te m ust b e p la c e d with the sa m e c a re a s wo uld b e fo llo we d in c o nstruc ting the silo wa lls. To e m p lo y no q ua lity c o ntro l o n e ithe r c o nc re te o r wo rkm a nship is una c c e p ta b le !

c . C e ntring Silo o n Fo o ting s

Lo a d -b e a ring wa lls sho uld b e c e ntre d o n fo o ting s whe ne ve r p o ssib le in o rd e r to a p p ly unifo rm lo a d s to the fo und a tio n so il a nd thus p e rmit full use o f its a llo wa b le b e a ring c a p a c ity.

La rg e fo und a tio ns a re re q uire d in so ft, we a k so ils to m a inta in a p p lie d p re ssure s within the a llo wa b le b e a ring c a p a c ity. La rg e -d ia m e te r ring fo und a tio ns p ro je c ting b e yo nd the silo wa lls a re o fte n use d to p ro vid e m a xim um sta b ility a g a inst o ve rturning . The inte rio r flo o r is usua lly o m itte d fo r re a so ns o f e c o no m y. The inne r d ia m e te r o f this fo und a tio n is no rm a lly slig htly le ss tha n the inne r d ia m e te r o f the silo wa ll. Be c a use the he a vy wa ll lo a d s a p p lie d to the inne r e d g e te nd to d e fo rm the ring fo und a tio n it c o uld e a sily b re a k into ind ivid ua l se c tio ns unle ss it is p ro p e rly re info rc e d . In this c a se the fo o ting p re ssure s wo uld no t b e unifo rm a nd lo c a l o ve rstre ssing o f the und e rlying so il c o uld o c c ur. With a d e q ua te re info rc ing , ho we ve r, a nd b y e xte nd ing the fo o ting furthe r insid e the silo , the c o nta c t p re ssure s wo uld b e re d istrib ute d m o re unifo rm ly a nd a ny te nd e nc y o f the fo und a tio n to d e fo rm wo uld b e re d uc e d . The a d d itio na l we ig ht o f the sila g e o n the e xte nd e d fo o ting wo uld b e m inim a l b e c a use m o st o f

the sila g e lo a d is tra nsfe rre d to the silo wa lls thro ug h fric tio n.

d . Silo G ro up s

To a vo id a ny inte ra c tio n b e twe e n silo s c o nstruc te d o n c o m p re ssib le c la ys lo a d e d to the a llo wa b le b e a ring c a p a c ity it is re c o m m e nd e d tha t the minim um ho rizo nta l c le a ra nc e b e twe e n the m sho uld b e no t le ss tha n the d ia m e te r o f the ring fo und a tio ns. If a sm a lle r sp a c ing is d e sire d , the silo s sho uld b e c o nstruc te d o n p ile s o r o n a c o m m o n m a t fo und a tio n a d e q ua te ly re info rc e d to re sist the a p p lie d b e nd ing m o m e nts.

e . Silo Lo a d

La rg e q ua ntitie s o f silo lo a d fo rm whe n the c o nte nts o f the silo s a re sto re d we t, i.e ., whe n the ir m o isture c o nte nt is to o g re a t. In to we r silo s c o nstruc te d witho ut flo o rs, the

liq uid c a n flo w und e r hig h hyd ro sta tic p re ssure into the fo und a tio n so il a nd und e rmine the fo und a tio ns. The y c a n inc re a se the p o re wa te r p re ssure s in sa tura te d c la y so ils, re d uc ing the she a r stre ng th. In a d d itio n, c he m ic a l re a c tio n with the so il m a y furthe r d e c re a se so il stre ng th.

An im p e rm e a b le flo o r sho uld b e insta lle d to p re ve nt a ny liq uid s fro m p e ne tra ting the sub so il, a nd d ra ins sho uld b e p ro vid e d to c a rry the m a wa y a nd re d uc e the hyd ro sta tic p re ssure s in the silo . It is im p o rta nt tha t the d ra ins c o ntinue to func tio n fo r the life o f the struc ture .

1.4 Be a ring C a p a c ity

The ultima te b e a ring c a p a c ity o f so ils d e p e nd s o n the she a r stre ng th (cu) o f the so il, a nd the

d e p th a nd sha p e o f fo und a tio n.

Whe n a silo o ve rturns the fo und a tio n so il ro ta te s a lo ng a c irc ula r a rc (Fig ure 2.1). The d ire c tio n o f the a p p lie d she a r stre ss a lo ng the slip c irc le c ha ng e s fro m 0 to 90 d e g fro m the ve rtic a l. In ra re c a se s the she a r stre ng th o f the so il is iso tro p ic (c o nsta nt in a ll d ire c tio ns), b ut g e ne ra lly it is a niso tro p ic (va rie s with the d ire c tio n o f a p p lie d she a r stre ss). Inve stig a tio ns o f m a rine c la ys ha ve sho wn o rie nta tio n d e p e nd e nt re d uc tio n in she a r stre ng th o f a s m uc h a s 35 p e r c e nt whe n c o m p a re d with the stre ng th m e a sure d in the ve rtic a l d ire c tio n. It is im p e ra tive , the re fo re , tha t a n a d e q ua te fa c to r o f sa fe ty sho uld b e inc lud e d to a llo w fo r stre ng th a niso tro p y, no n-unifo rm p re ssure s a p p lie d to the so il d ue to e c c e ntric lo a d s a nd o ve rturning m o m e nts fro m hig h wind s, a nd to p re ve nt e xc e ssive ve rtic a l se ttle m e nts. This fa c to r o f sa fe ty is a p p lie d to the

she a r stre ng th o f the so il. (a fte r M. Bo zo zuk, 1976)

2. Analytical Design

2.1 Pa d Fo und a tio n

Ta b e l 1. Be a ring C a p a c ity o f Pa d Fo und a tio n

Layer

Depth (m)

cu

(kPa)

v

σ

(kPa) qult

(kPa)

1 0.6 60 0.00 386.43

1 2.2 60 46.20 432.63

2 4.65 30 72.87 266.10

3 7.07 35 94.90 320.30

4 11.25 25 137.30 297.90

Se ttle m e nt:

Ta b le 2. Se ttle m e nt o f Pa d Fo und a tio n

Depth (m)

ρi

(mm)

ρc(centre)

(mm)

ρc(corner)

(mm)

ρc(side)

(mm)

ρdiff

(mm)

ρ(total)

(mm)

18 23 123.8 52.8 74.3 71 146

Pa ra m e tric Stud ie s:

Ta b le 3. Be a ring C a p a c ity with d iffe re nt stre ng th p ro p e rtie s o f the so il

cu

(kPa)

qult

(kPa) FoS Increase in FoS

40 257.62 1.31 -51%

50 322.02 1.64 -20%

60 386.43 1.97 0.0%

70 450.83 2.30 +17.0%

2.2 Strip Fo und a tio n

Ta b le 4. Be a ring C a p a c ity o f Strip Fo und a tio n

Layer

Depth (m)

cu

(kPa)

v

σ

(kPa)

1 0.6 60 0.00

1 2.2 60 46.20

2 4.65 30 72.87 3 7.07 35 94.90 4 11.25 25 137.30

Se ttle m e nt:

Ta b le 5. Se ttle m e nt o f Strip Fo und a tio n

Depth (m)

ρi

(mm)

ρc(centre)

(mm)

ρc(corner)

(mm)

ρc(side)

(mm)

ρdiff

(mm)

ρ(total)

(mm)

18m 18.8 118 33 59 85 137

Pa ra m e tric Stud ie s:

Ta b le 6. Be a ring C a p a c ity with d iffe re nt stre ng th p ro p e rtie s o f the so il

No cu

(kPa)

qult

(kPa) FoS

1 40 223.43 2.87 2 50 279.30 3.59 3 60 335.14 4.31 4 70 391.00 5.03 5 80 446.85 5.76

2.3 Pile Fo und a tio n

Be a ring C a p a c ity:

Ta b le 7. Be a ring C a p a c ity o f Sing le Pile

Depth (m)

Qb

(kN) Qs

(kPa) Qult

(kPa) qn

(kPa) FoS

18 108 1221 282 488 2.73

• C he c king b y Euro c o d e

Rc d > qn = 678.8kN > 488kN, This is sa tisfa c to ry

Se ttle m e nt;

Ta b le 8. Se ttle m e nt o f Pile Fo und a tio n

Depth (m)

ρicentre

(mm)

ρi(corner)

(mm)

ρi(side)

(mm)

Ρaverag

(mm)

Ρ(total)

(mm)

18 48 12 43 35 21

Pa ra m e tric Stud ie s:

Ta b le 9. Be a ring C a p a c ity with d iffe re nt stre ng th p ro p e rtie s o f the so il

cu

(kPa)

Qb

(kPa)

Qs

(kPa)

FoS

Change Bearing Capacity

60 81.09 1129.98 2.28 -19.5%

70 94.61 1175.80 2.60 -4.6%

80 108.15 1221.60 2.72 0.0%

90 121.64 1269.95 2.85 +4.8%

3. Numerical Design

In this c ha p te r the d e sig n o f typ e s o f fo und a tio n in the p re vio us c ha p te r will b e re vie we d a nd e xa m ine d using the finite e le m e nt a p p ro a c h with the he lp o f a c o m p ute r p ro g ra m m e SAFE in O ASYS-G EO 17.9. The inp ut a nd o utp ut

p a ra m e te rs a re the sa m e a s the p a ra m e te rs in the a na lytic a l d e sig n. A stud y a b o ut va ria tio n o f p a ra m e te rs a nd c o nve rg e nc e stud y will b e p ro d uc e .

3.1 Pa d Fo und a tio n

Ta b le 10. Re sults o f the finite e le m e nt m o d e lling c o m p a re d to the a na lytic a l so lutio ns

Parameter Analytical

Result

Numerical Result

Difference (%)

FoS 1.97 1.25 57

Settlement 122 44 199

Pa ra m e tric Stud y:

• Be a ring C a p a c ity

Ta b le 11. Fa ilure lo a d fo r runs with d iffe re nt stre ng th p ro p e rtie s o f the so il

cu

(kPa)

Failure Load

(kN/m2) FoS

Change in Bearing Capacity

40 204 < q < 206 1.05 -19.1% 50 224 < q < 226 1.15 -8.6%

60 243 < q < 245 1.25 0.0%

70 261 < q < 263 1.34 +7.5%

80 277 < q < 279 1.42 +13.7%

• Se ttle m e nt

0 100 200 300 400 500

0 250 500 750 1000 1250 1500 1750 2000

Loa

d (

k

N

/m

)

Settlement (mm)

(Cu=80) Cu=70) (Cu=60)

Fig ure 4. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r inc re a sing so il stre ng th.

0 100 200 300 400 500

0 250 500 750 1000 1250 1500 1750 2000

Lo

a

d

(

k

N

/m

)

Settlement (mm)

(Cu=40) Cu=50) (Cu=60)

Fig ure 5. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th

3.2 Strip Fo und a tio n

Ta b le 12. Re sults o f the finite e le m e nt m o d e lling c o m p a re d to the a na lytic a l so lutio ns

Parameter

Analytical Result

Numerical Result

Difference (%)

Fo S 4.2 2.6 61.5

Se ttle m e nt 137m m 98m m 40.0

Pa ra m e tric Stud y:

• Be a ring C a p a c ity

Ta b le 13. Fa ilure lo a d fo r runs with d iffe re nt stre ng th p ro p e rtie s o f the so il

Cu (kPa)

Failure Load

(kN/m2) FoS

Change In FoS

40 172 < q < 174 2.05 -21.7%

50 186 < q < 188 2.37 -9.5%

60 203 < q < 205 2.62 0.0%

70 222 < q < 224 2.82 +7.8% 80 246 < q < 248 3.03 +15.7

• Se ttle m e nt

0 50 100 150 200 250 300

0 250 500 750 1000 1250 1500 1750 2000

Loa

d (

k

N

/m

)

Settlement (mm)

(Cu=80) Cu=70) (Cu=60)

Fig ure 6. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th.

0 50 100 150 200 250 300

0 250 500 750 1000 1250 1500 1750 2000

Loa

d (k

N

/m

)

Settlement (mm)

(Cu=40) Cu=50) (Cu=60)

Fig ure 7. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th.

3.3 Pile Fo und a tio n

Ta b le 14. Re sults o f the finite e le m e nt m o d e lling c o m p a re d to the a na lytic a l so lutio ns

Parameter Analytical

Result

Numerical Result

Difference (%)

Fo S 2.73 1.75 56

Pa ra m e tric Stud y:

• Be a ring C a p a c ity

Ta b le 15. Fa ilure lo a d fo r runs with d iffe re nt stre ng th p ro p e rtie s o f the so il

Cu (kPa) Failure Load

(kN/m2) FoS

Change in Bearing Capacity

40 178 < q < 180 1.53 -14.5%

50 191 < q < 193 1.64 -6.6%

60 201 < q < 203 1.75 0.0%

70 208 < q < 210 1.78 +1.8%

80 220 < q < 222 1.89 +8.0%

• Se ttle m e nt

0 50 100 150 200 250 300 350

0 500 1000 1500 2000 2500 3000 3500 4000

Lo

a

d (

k

N

/m

)

Settlement (mm)

(Cu=80) Cu=70) (Cu=60)

Fig ure 8. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r inc re a sing so il stre ng th.

0 50 100 150 200 250 300 350

0 500 1000 1500 2000 2500 3000 3500 4000

Loa

d (

k

N

/m

)

Settlement (mm)

(Cu=40) Cu=50) (Cu=60)

Fig ure 9. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th.

4. Discussion

The a na lytic a l a nd num e ric a l d e sig n stud ie s we re b a se d o n the sa m e d a ta inp ut. Ne ve rthe le ss b o th o f the m e tho d s usua lly p ro d uc e d iffe re nt re sults.

4.1 Pa d Fo und a tio n

Ac c o rd ing to the a na lytic a l a nd num e ric a l p re d ic tio ns sho we d tha t the p a d fo und a tio n se e m s unsa tisfa c to ry to sup p o rt the silo s. The re a re se ve ra l fa c to rs b a se o f tho se re a so n. In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring fa ilure is 1.92 whic h is lo we r tha n the limit va lue o f fa ilure (

2

.

5

). In a d d itio n, a t the se c o nd la ye r o f so ils the va lue o f fa c to r o f sa fe ty d e c re a se d to 1.36 whic h is unsa tisfa c to ry. And a t the third a nd fo urth la ye r the va lue o f fa c to r o f sa fe ty wa s fluc tua te d to b e 1.63 a nd 1.52 re sp e c tive ly.

The num e ric a l re sult a na lysis a p p e a rs tha t the va lue o f fa c to r o f sa fe ty a g a inst b e a ring fa ilure slig htly lo we r tha n the a na lytic a l m e tho d . The fa c to r o f sa fe ty wa s p ro d uc e d b y num e ric a l a na lysis o f 1.25 tha t it is lo we r tha n the limit va lue o f fa c to r o f sa fe ty. It c a n b e c o nc lud e tha t num e ric a l m e tho d p ro d uc e s lo we r re sults tha n a na lytic a l d e sig n.

The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d tha t the se ttle m e nt se e m e d a p ro b le m in the p a d fo und a tio n. It c a n b e se e n fro m Ta b le 10 tha t the a na lytic a l a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 122m m a nd 41m m re sp e c tive ly. Whic h is the se ttle m e nt is in c ritic a l c o nd itio n. In a d d itio n, the d iffe re nc e se ttle m e nt p ro vid e s b y a na lytic a l m e tho d is a p p ro xim a te ly 71.04m m , tha t is c a n c a use the c ra c k o n the to p o f

fo und a tio n a nd will im p a c t the sta b ility o f the silo s. Whe n the p a ra m e tric stud y b e e n p ro c e ss to d e c re a se a nd inc re a se o f the stre ng th o f the so il, a c ha ng e o f se ttle m e nt b y b o th stud y a re 17% a nd 20% re sp e c tive ly, whe re it se e m e d no t re a lly im p o rta nt e ffe c t o f the se ttle m e nts a s sho wn in ta b le 10 a nd fig ure 6 a nd 7.

As the lo w o f fa c to r o f sa fe ty in c a se o f p a d fo und a tio n d e sig n, it se e m s tha t so m e fa c to r c o uld b e a p ro b le m in the te rm o f the p a d fo und a tio n b e e n a p p lie d . First, p la stic d e fo rm a tio n mig ht b e p re se nt d ue to the inc o nsiste nc y o f the fa c to r o f sa fe ty in se ve ra l la ye rs, le a d ing to m o ve m e nt o f the fo und a tio n g re a te r tha n se ttle m e nts; in e xtre m e c a se fa ilure will o c c ur.

Ano the r p ro b le m tha t c o uld b e o c c ur a nd sho uld b e ta ke n und e r c o nsid e ra tio n is the no n-unifo rm p la c e m e nt o f fill d uring filling . Whe n the lo a d fro m the c o nte nt a nd the silo s is o ff c e ntre , a s the re sult, the p re ssure b ulb will b e d iso rd e r, a s sho wn in fig ure 2. Stro ng wind s a c ting o n ta ll silo c a n p ro d uc e the sa m e e ffe c t. The lo c a l o ve rstre ssing o f the fo und a tio n so il m a y c a use tilting , a nd unle ss the p ro b le m is re m e d ie d it m a y inc re a se with tim e until the silo o ve rturns.

If two o r m o re silo s a re c o nstruc te d to o c lo se to e a c h o the r, c o nse q ue ntly, the p re ssure b ulb will o ve rla p , a s sho wn in fig ure 3. Be c a use o f p re ssure a re a d d itive , the re sulting p re ssure b ulb will b e m uc h la rg e r a nd will e xte nd to g re a te r d e p ths. In the o ve rla p zo ne , the so il will b e sub je c te d to hig he r stre sse s a nd the fo und a tio n in this re g io n will b e se ttling m o re , c a using the silo s to tilt to wa rd e a c h o the r.

The c o nstruc tio n c o st fo r the p a d fo und a tio n will b e ve ry e xp e nsive , b e c a use it is re q uire d la rg e a m o unt o f c o nc re te a nd lo ng tim e c o nstruc tio n p ro c e ss. It is a lso re q uire d a d va nc e o f site inve stig a tio n to se c ure o f sta b ility o f the silo s in lo ng -te rm p e rio d . And the sp a c e c o uld b e a p ro b le m fo r c o nstruc ting the p a d in the site d ue to the limita tio n o f the a re a .

4.2 Strip Fo und a tio n

As c a n b e e n se e n fro m the a na lytic a l a nd num e ric a l p re d ic tio ns, tha t sho we d the strip fo und a tio n se e m s fe a sib le to sup p o rt the silo s in te rm o f fa c to r o f sa fe ty. The re a re se ve ra l fa c to rs b a se o f tho se re a so n. In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring fa ilure is 4.2 whic h is sa tisfa c to ry. In a d d itio n, a t the se c o nd la ye r o f so ils the va lue o f fa c to r o f sa fe ty d e c re a se d to 3.0 whic h is sa tisfa c to ry. And a t the third a nd fo urth la ye r the va lue o f fa c to r o f sa fe ty wa s c o nsiste nc e d e c re a se in 3.6 a nd 3.5 re sp e c tive ly. Ho we ve r, the num e ric a l re sult a na lysis a p p e a rs tha t the va lue o f fa c to r o f sa fe ty a g a inst b e a ring fa ilure lo we r tha n the a na lytic a l m e tho d . The fa c to r o f sa fe ty wa s p ro d uc e d b y num e ric a l a na lysis a p p ro xim a te ly 2.6 tha t it is ne a r to the limit va lue o f fa c to r o f sa fe ty o f 2.5. It se e m s tha t the num e ric a l m e tho d p ro d uc e s lo we r re sults tha n a na lytic a l d e sig n.

The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d tha t the se ttle m e nt is b ig c a se tha t re a lly a p ro b le m in te rm o f strip fo und a tio n b e e n a p p lie d . It c a n b e se e n fro m Ta b le 12 tha t the a na lytic a l a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 137m m a nd 98m m re sp e c tive ly. Whic h is the se ttle m e nt is

in c ritic a l c o nd itio n. In o the r ha nd , the d iffe re nc e se ttle m e nt sho we d b y a na lytic a l m e tho d is ve ry hig h tha t it is a p p ro xim a te ly 85m m , tha t it is c a n c a use the c ra c k o n the to p o f fo und a tio n a nd will im p a c t the sta b ility o f the struc ture o f the silo s. In e xtre m e c a se c a n c a use the fa ilure o f the silo s.

As the hig h o f the se ttle m e nt a nd the d iffe re nc e se ttle m e nt p re d ic te d in strip fo und a tio n d e sig n, it c a n b e c o nc lud e tha t the strip fo und a tio n unfe a sib le fo r the silo s. Furthe rm o re , nine silo s b uild in the ro w re q uire s la rg e o f sp a c e a lo ng the d o c ks, unfo rtuna te ly, lim ite d sp a c e is a p ro b le m in the site d ue to e xisting struc ture .

The c o nstruc tio n c o st fo r the strip fo und a tio n will b e ve ry e xp e nsive , b e c a use it is re q uire d la rg e a m o unt o f c o nc re te a nd lo ng tim e c o nstruc tio n p ro c e ss. It is a lso re q uire d a d va nc e o f site inve stig a tio n to se c ure o f sta b ility o f the silo s in lo ng -te rm p e rio d .

4.3 Pile Fo und a tio n

Ac c o rd ing to the a na lytic a l re sult tha t p ile fo und a tio n is fe a sib le fo r the silo s, whic h the se ttle m e nt p re d ic te d is a p p ro xim a te ly 21m m tha t is c a n b e ne g le c te d , So tha t the re sults o b ta ine d p ro ve tha t the p ile fo und a tio n is c o nsid e re d to the m o st fe a sib le c ho ic e fo r sup p o rt the silo s. Furthe rm o re , the num e ric a l p re d ic tio ns sho we d a s sa m e a s a na lytic a l p re d ic tio n tha t the p ile fo und a tio n se e m s sa tisfa c to ry to sup p o rt the silo s. In the o the r ha nd , c he c king b y Euro c o d e tha t a ll the c o nd itio ns ha d b e e n sa tisfie d fo r the sa fe ty o f the struc ture . Tha t m e a ns tha t the little d iffe re nc e in p re d ic tio n b e twe e n num e ric a l a nd a na lytic a l is no t re a lly sig nific a nt tha t c a n a ffe c t

the struc ture . It c o uld b e c o nc lud e a s sa tisfa c to ry.

In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring fa ilure is 2.73 whic h is hig he r tha n the limit va lue tha t ha ve b e e n g ive n (2.5). Ho we ve r, a t the p ile g ro up a na lysis, the va lue o f fa c to r o f sa fe ty is ve ry hig h a p p ro xim a te ly 9.6 whic h it is sa tisfa c to ry. In o the r ha nd , num e ric a l p re d ic tio n is ra the r p e ssim istic whe re the fa c to r o f sa fe ty wa s p re se nte d a p p ro xim a te ly 1.75. The fa c to r tha t c a use d the lo w o f fa c to r sa fe ty p ro d uc e b y num e ric a l c o uld b e the la c k o f so il info rm a tio n tha t p re se nte d a nd the c o nse rva tive a ssum p tio n tha t b e e n c ho se n in o rd e r to c a rry o ut the d e sig n p ro c e d ure . In a d d itio n, the g ro und wa te r le ve l wa s b e e n ta ke n ra the r c o nse rva tive , while it ha s im p o rta nt e ffe c t o n ultim a te b e a ring c a p a c ity o f fo und a tio n. With the hig h g ro und wa te r le ve ls, the e ffe c tive stre sse s in the g ro und a re lo we r tha n whe n the so ils im m e d ia te ly b e lo w the fo und a tio n a re d ry, a nd the ultim a te b e a ring c a p a c ity is re d uc e d .

The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d tha t the se ttle m e nt is no t re a lly a p ro b le m in the p ile fo und a tio n. It c a n b e se e n fro m Ta b le 14 tha t the a na lytic a l a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 21m m a nd 19.1m m re sp e c tive ly. Whic h it is c a n b e ne g le c te d . The d iffe re nc e a b o ut the p re d ic tio n o f the se ttle m e nt a na lysis b y b o th m e tho d s is a p p ro xim a te ly 10%.

Ma ny typ e s o f p ile fo r sup p o rt the silo s struc ture a re a va ila b le . Drive n a nd c a st in p la c e s p ile s a re e c o no m ic a l fo r la nd struc ture . But the g ro und he a ve a nd the vib ra tio n a sso c ia te d with the insta lla tio n c a n c a use d e sta b iliza tio n o f q ua y wa ll.

Bo re d a nd c a st in the p la c e a re the c he a p e st typ e s o f the p ile , whic h it is p o ssib le to b e c ho se n b e c a use it will ke e p the c o st o f fo und a tio n e ffic ie ntly.

The c o nstruc tio n c o st fo r the p ile fo und a tio n will b e c he a p e r tha n o the r typ e s o f fo und a tio n, b e c a use it is no t re q uire d la rg e a m o unt o f c o nc re te a nd sho rt tim e c o nstruc tio n p ro c e ss.

5. Conclusion

As the re sult o f a na lytic a l a nd num e ric a l d e sig n o f the fo und a tio n fo r sup p o rt the silo s, the re a re se ve ra l p o int tha t c a n b e c o nc lud e :

a . The p a d fo und a tio n p ro ve d to b e unsuita b le fro m a ny a sp e c ts o f fo und a tio n d e sig n, a s c a n b e e n se e n fro m the re sults o f fa c to r o f sa fe ty a g a inst fa ilure we re unsa tisfa c to ry p re d ic te d b o th b y a na lytic a l a nd num e ric a l m e tho d s. Whe re it c o uld b e c a use p la stic d e fo rm a tio n within the so il. Furthe rm o re , t will le a d to m o ve m e nt o f the fo und a tio n g re a te r tha n se ttle m e nts; in e xtre m e c a se fa ilure will o c c ur. Furthe rm o re , the p a d fo und a tio n will b e e xp e nsive struc ture d ue to re q uire d la rg e q ua ntity o f c o nc re te a nd tim e c o nsum ing . b . In the te rm s o f fa c to r o f sa fe ty the

strip fo und a tio n se e m e d to b e fe a sib le fo r the silo s. Be c a use the hig h va lue o f fa c to r o f sa fe ty p re d ic te d b y a na lytic a l m e tho d s. Ho we ve r, the se ttle m e nt is re a lly a c ritic a l p ro b le m tha t fa c e d b y strip fo und a tio n. Bo th num e ric a l a nd a na lytic a l p re d ic te d the c ritic a l va lue o f se ttle m e nt. In a d d itio n, the d iffe re nc e se ttle m e nt sho we d b y a na lytic a l m e tho d is ve ry hig h tha t it c a n c a use the c ra c k o n the to p o f fo und a tio n a nd will im p a c t

the silo ’ s struc ture . As the hig h o f the se ttle m e nt a nd the d iffe re nc e se ttle m e nt p re d ic te d in strip fo und a tio n d e sig n, it c a n b e c o nc lud e tha t the strip fo und a tio n is unre lia b le fo r the silo s. Furthe rm o re , nine silo s b uild in the ro w re q uire s la rg e o f sp a c e a lo ng the d o c ks, unfo rtuna te ly, limite d sp a c e is a p ro b le m in the site d ue to e xisting struc ture o n the site . c . Ana lytic a l a nd num e ric a l re sults

o b ta ine d p ro ve tha t the p ile fo und a tio n is c o nsid e re d to the m o st fe a sib le c ho ic e fo r sup p o rt the silo s. Furthe rm o re , the num e ric a l p re d ic tio ns sho we d a s sa m e a s a na lytic a l p re d ic tio n tha t the p ile fo und a tio n se e m s sa tisfa c to ry to sup p o rt the silo s. In the o the r ha nd , c he c king b y Euro c o d e tha t a ll the c o nd itio ns ha d b e e n sa tisfie d fo r the sa fe ty o f the struc ture . Bo re d a nd c a st in the p la c e a re the c he a p e st typ e s o f the p ile , whic h it is p o ssib le to b e c ho se n b e c a use it will ke e p the c o st o f fo und a tio n e ffic ie ntly. The c o nstruc tio n c o st fo r the p ile fo und a tio n will b e c he a p e r tha n o the r typ e s o f fo und a tio n, b e c a use it is no t re q uire d la rg e a m o unt o f c o nc re te a nd sho rt tim e c o nstruc tio n p ro c e ss.

6. References

Ang ush J. Ma c Do na ld , 1975, Wind lo a d ing o n b uild ing s, p ub lishe d b y Ap p lie d Sc ie nc e Pub lishe r LTD, 1975.

British Sta nd a rd : 8004, 1986. C o de o f p ra c tic e fo r fo unda tio n. Annua l b o o k o f British Sta nd a rd , 1986.

Burla nd , J.B, a nd Wro th, C .P. 1974.

Se ttle me nt o f b uilding a nd a sso c ia te d da ma g e . Re vie w

p a p e r, se ssio n V.611-54.

Se ttle me nt o f struc ture s. Pe nte c h p re ss. Lo nd o n Euro c o d e 7: G e o te c hnic a l De sig n

Pa rt 1: G e ne ra l Rule s (ENV 1997-1)

H. Unwin & R.A Je sse p , 2004, Lo ng te rm p ile te sting in Lo nd o n c la y: a c a se study. In:

Pro c e e ding s o f the Institute o f

c ivil e ng ine e ring , G e o e te c hnic a l

e ng ine e ring 157, Issue G E2

(2004), p p . 57-63

G .E. Ba rne s, 2000, So il Me c ha nic s: p rinc ip le a nd p ra c tic e , se c o nd e d itio n, p ub lishe d b y Pa lg ra ve Ltd .

M.B Ja ksa e t a ll, 2005, To wa rd sre lia b le a nd e ffe c tive site inve stig a tio n, G e o te c hniq ue

55, No . 2 (2005), p p . 109-121. M.J. To m linso n, 1995, Fo unda tio n

d e sig n a nd c o nstruc tio n, sixth e d itio n, p ub lishe d b y Lo ng m a n Sc ie ntific & Te c hnic a l 1995.

M. Bo zo zuk, 1976, To we r Silo Fo und a tio ns, Pub lishe d b y C a na d ia n Build ing Dig e st. O ASYS-G EO 17.9 He lp Ma nua l,

2002-2005.

Ste wa rt B.,2004-2005, Le c ture s no te s in fo unda tio n e ng ine e ring, Unive rsity o f G la sg o w.

Va n Im p e & Ha e g e m a n,1998, De e p Fo unda tio n o n Bo re d a nd Aug e r p ile s. “ La rg e dia me te r b o re d p ile s in multi-la ye re d so ils o f Ba ng ko k”. Ba lke na , Ro tte rd a m .

• Se ttle m e nt

0 50 100 150 200 250 300

0 250 500 750 1000 1250 1500 1750 2000

Loa

d (

k

N

/m

)

Settlement (mm)

(Cu=80) Cu=70) (Cu=60)

Fig ure 6. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th.

0 50 100 150 200 250 300

0 250 500 750 1000 1250 1500 1750 2000

Loa

d (k

N

/m

)

Settlement (mm)

(Cu=40) Cu=50) (Cu=60)

Fig ure 7. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th.

3.3 Pile Fo und a tio n

Ta b le 14. Re sults o f the finite e le m e nt m o d e lling c o m p a re d to the a na lytic a l so lutio ns Parameter Analytical

Result

Numerical Result

Difference (%) Fo S 2.73 1.75 56

Pa ra m e tric Stud y:

• Be a ring C a p a c ity

Ta b le 15. Fa ilure lo a d fo r runs with d iffe re nt stre ng th p ro p e rtie s o f the so il

Cu (kPa) Failure Load

(kN/m2) FoS

Change in Bearing Capacity

40 178 < q < 180 1.53 -14.5%

50 191 < q < 193 1.64 -6.6%

60 201 < q < 203 1.75 0.0%

70 208 < q < 210 1.78 +1.8%

80 220 < q < 222 1.89 +8.0%

• Se ttle m e nt

0 50 100 150 200 250 300 350

0 500 1000 1500 2000 2500 3000 3500 4000

Lo

a

d (

k

N

/m

)

Settlement (mm)

(Cu=80) Cu=70) (Cu=60)

Fig ure 8. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r inc re a sing so il stre ng th.

0 50 100 150 200 250 300 350

0 500 1000 1500 2000 2500 3000 3500 4000

Loa

d (

k

N

/m

)

Settlement (mm)

(Cu=40) Cu=50) (Cu=60)

Fig ure 9. Se ttle m e nt ve rsus inc re m e nta l lo a d ing fo r d e c re a sing so il stre ng th.

4. Discussion

The a na lytic a l a nd num e ric a l d e sig n stud ie s we re b a se d o n the sa m e d a ta inp ut. Ne ve rthe le ss b o th o f the m e tho d s usua lly p ro d uc e d iffe re nt re sults.

4.1 Pa d Fo und a tio n

Ac c o rd ing to the a na lytic a l a nd num e ric a l p re d ic tio ns sho we d tha t the p a d fo und a tio n se e m s unsa tisfa c to ry to sup p o rt the silo s. The re a re se ve ra l fa c to rs b a se o f tho se re a so n. In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring fa ilure is 1.92 whic h is lo we r tha n the limit va lue o f fa ilure (

2

.

5

). In a d d itio n, a t the se c o nd la ye r o f so ils the va lue o f fa c to r o f sa fe ty d e c re a se d to 1.36 whic h is unsa tisfa c to ry. And a t the third a nd fo urth la ye r the va lue o f fa c to r o f sa fe ty wa s fluc tua te d to b e 1.63 a nd 1.52 re sp e c tive ly.

The num e ric a l re sult a na lysis a p p e a rs tha t the va lue o f fa c to r o f sa fe ty a g a inst b e a ring fa ilure slig htly lo we r tha n the a na lytic a l m e tho d . The fa c to r o f sa fe ty wa s p ro d uc e d b y num e ric a l a na lysis o f 1.25 tha t it is lo we r tha n the limit va lue o f fa c to r o f sa fe ty. It c a n b e c o nc lud e tha t num e ric a l m e tho d p ro d uc e s lo we r re sults tha n a na lytic a l d e sig n.

The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d tha t the se ttle m e nt se e m e d a p ro b le m in the p a d fo und a tio n. It c a n b e se e n fro m Ta b le 10 tha t the a na lytic a l a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 122m m a nd 41m m re sp e c tive ly. Whic h is the se ttle m e nt is in c ritic a l c o nd itio n. In a d d itio n, the d iffe re nc e se ttle m e nt p ro vid e s b y a na lytic a l m e tho d is a p p ro xim a te ly 71.04m m , tha t is c a n c a use the c ra c k o n the to p o f

fo und a tio n a nd will im p a c t the sta b ility o f the silo s. Whe n the p a ra m e tric stud y b e e n p ro c e ss to d e c re a se a nd inc re a se o f the stre ng th o f the so il, a c ha ng e o f se ttle m e nt b y b o th stud y a re 17% a nd 20% re sp e c tive ly, whe re it se e m e d no t re a lly im p o rta nt e ffe c t o f the se ttle m e nts a s sho wn in ta b le 10 a nd fig ure 6 a nd 7.

As the lo w o f fa c to r o f sa fe ty in c a se o f p a d fo und a tio n d e sig n, it se e m s tha t so m e fa c to r c o uld b e a p ro b le m in the te rm o f the p a d fo und a tio n b e e n a p p lie d . First, p la stic d e fo rm a tio n mig ht b e p re se nt d ue to the inc o nsiste nc y o f the fa c to r o f sa fe ty in se ve ra l la ye rs, le a d ing to m o ve m e nt o f the fo und a tio n g re a te r tha n se ttle m e nts; in e xtre m e c a se fa ilure will o c c ur.

Ano the r p ro b le m tha t c o uld b e o c c ur a nd sho uld b e ta ke n und e r c o nsid e ra tio n is the no n-unifo rm p la c e m e nt o f fill d uring filling . Whe n the lo a d fro m the c o nte nt a nd the silo s is o ff c e ntre , a s the re sult, the p re ssure b ulb will b e d iso rd e r, a s sho wn in fig ure 2. Stro ng wind s a c ting o n ta ll silo c a n p ro d uc e the sa m e e ffe c t. The lo c a l o ve rstre ssing o f the fo und a tio n so il m a y c a use tilting , a nd unle ss the p ro b le m is re m e d ie d it m a y inc re a se with tim e until the silo o ve rturns.

If two o r m o re silo s a re c o nstruc te d to o c lo se to e a c h o the r, c o nse q ue ntly, the p re ssure b ulb will o ve rla p , a s sho wn in fig ure 3. Be c a use o f p re ssure a re a d d itive , the re sulting p re ssure b ulb will b e m uc h la rg e r a nd will e xte nd to g re a te r d e p ths. In the o ve rla p zo ne , the so il will b e sub je c te d to hig he r stre sse s a nd the fo und a tio n in this re g io n will b e se ttling m o re , c a using the silo s to tilt to wa rd e a c h o the r.

The c o nstruc tio n c o st fo r the p a d fo und a tio n will b e ve ry e xp e nsive , b e c a use it is re q uire d la rg e a m o unt o f c o nc re te a nd lo ng tim e c o nstruc tio n p ro c e ss. It is a lso re q uire d a d va nc e o f site inve stig a tio n to se c ure o f sta b ility o f the silo s in lo ng -te rm p e rio d . And the sp a c e c o uld b e a p ro b le m fo r c o nstruc ting the p a d in the site d ue to the limita tio n o f the a re a .

4.2 Strip Fo und a tio n

As c a n b e e n se e n fro m the a na lytic a l a nd num e ric a l p re d ic tio ns, tha t sho we d the strip fo und a tio n se e m s fe a sib le to sup p o rt the silo s in te rm o f fa c to r o f sa fe ty. The re a re se ve ra l fa c to rs b a se o f tho se re a so n. In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring fa ilure is 4.2 whic h is sa tisfa c to ry. In a d d itio n, a t the se c o nd la ye r o f so ils the va lue o f fa c to r o f sa fe ty d e c re a se d to 3.0 whic h is sa tisfa c to ry. And a t the third a nd fo urth la ye r the va lue o f fa c to r o f sa fe ty wa s c o nsiste nc e d e c re a se in 3.6 a nd 3.5 re sp e c tive ly. Ho we ve r, the num e ric a l re sult a na lysis a p p e a rs tha t the va lue o f fa c to r o f sa fe ty a g a inst b e a ring fa ilure lo we r tha n the a na lytic a l m e tho d . The fa c to r o f sa fe ty wa s p ro d uc e d b y num e ric a l a na lysis a p p ro xim a te ly 2.6 tha t it is ne a r to the limit va lue o f fa c to r o f sa fe ty o f 2.5. It se e m s tha t the num e ric a l m e tho d p ro d uc e s lo we r re sults tha n a na lytic a l d e sig n.

The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d tha t the se ttle m e nt is b ig c a se tha t re a lly a p ro b le m in te rm o f strip fo und a tio n b e e n a p p lie d . It c a n b e se e n fro m Ta b le 12 tha t the a na lytic a l a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 137m m a nd 98m m re sp e c tive ly. Whic h is the se ttle m e nt is

in c ritic a l c o nd itio n. In o the r ha nd , the d iffe re nc e se ttle m e nt sho we d b y a na lytic a l m e tho d is ve ry hig h tha t it is a p p ro xim a te ly 85m m , tha t it is c a n c a use the c ra c k o n the to p o f fo und a tio n a nd will im p a c t the sta b ility o f the struc ture o f the silo s. In e xtre m e c a se c a n c a use the fa ilure o f the silo s.

As the hig h o f the se ttle m e nt a nd the d iffe re nc e se ttle m e nt p re d ic te d in strip fo und a tio n d e sig n, it c a n b e c o nc lud e tha t the strip fo und a tio n unfe a sib le fo r the silo s. Furthe rm o re , nine silo s b uild in the ro w re q uire s la rg e o f sp a c e a lo ng the d o c ks, unfo rtuna te ly, lim ite d sp a c e is a p ro b le m in the site d ue to e xisting struc ture .

The c o nstruc tio n c o st fo r the strip fo und a tio n will b e ve ry e xp e nsive , b e c a use it is re q uire d la rg e a m o unt o f c o nc re te a nd lo ng tim e c o nstruc tio n p ro c e ss. It is a lso re q uire d a d va nc e o f site inve stig a tio n to se c ure o f sta b ility o f the silo s in lo ng -te rm p e rio d .

4.3 Pile Fo und a tio n

Ac c o rd ing to the a na lytic a l re sult tha t p ile fo und a tio n is fe a sib le fo r the silo s, whic h the se ttle m e nt p re d ic te d is a p p ro xim a te ly 21m m tha t is c a n b e ne g le c te d , So tha t the re sults o b ta ine d p ro ve tha t the p ile fo und a tio n is c o nsid e re d to the m o st fe a sib le c ho ic e fo r sup p o rt the silo s. Furthe rm o re , the num e ric a l p re d ic tio ns sho we d a s sa m e a s a na lytic a l p re d ic tio n tha t the p ile fo und a tio n se e m s sa tisfa c to ry to sup p o rt the silo s. In the o the r ha nd , c he c king b y Euro c o d e tha t a ll the c o nd itio ns ha d b e e n sa tisfie d fo r the sa fe ty o f the struc ture . Tha t m e a ns tha t the little d iffe re nc e in p re d ic tio n b e twe e n num e ric a l a nd a na lytic a l is no t re a lly sig nific a nt tha t c a n a ffe c t

the struc ture . It c o uld b e c o nc lud e a s sa tisfa c to ry.

In te rm o f b e a ring c a p a c ity fa c to r p ro d uc e d b y a na lytic a l m e tho d sho ws tha t the va lue o f fa c to r sa fe ty a g a inst b e a ring fa ilure is 2.73 whic h is hig he r tha n the limit va lue tha t ha ve b e e n g ive n (2.5). Ho we ve r, a t the p ile g ro up a na lysis, the va lue o f fa c to r o f sa fe ty is ve ry hig h a p p ro xim a te ly 9.6 whic h it is sa tisfa c to ry. In o the r ha nd , num e ric a l p re d ic tio n is ra the r p e ssim istic whe re the fa c to r o f sa fe ty wa s p re se nte d a p p ro xim a te ly 1.75. The fa c to r tha t c a use d the lo w o f fa c to r sa fe ty p ro d uc e b y num e ric a l c o uld b e the la c k o f so il info rm a tio n tha t p re se nte d a nd the c o nse rva tive a ssum p tio n tha t b e e n c ho se n in o rd e r to c a rry o ut the d e sig n p ro c e d ure . In a d d itio n, the g ro und wa te r le ve l wa s b e e n ta ke n ra the r c o nse rva tive , while it ha s im p o rta nt e ffe c t o n ultim a te b e a ring c a p a c ity o f fo und a tio n. With the hig h g ro und wa te r le ve ls, the e ffe c tive stre sse s in the g ro und a re lo we r tha n whe n the so ils im m e d ia te ly b e lo w the fo und a tio n a re d ry, a nd the ultim a te b e a ring c a p a c ity is re d uc e d .

The se ttle m e nt a na lysis p e rfo rm e d b y b o th m e tho d s sho we d tha t the se ttle m e nt is no t re a lly a p ro b le m in the p ile fo und a tio n. It c a n b e se e n fro m Ta b le 14 tha t the a na lytic a l a nd num e ric a l re sults p re se nt the se ttle m e nt a b o ut 21m m a nd 19.1m m re sp e c tive ly. Whic h it is c a n b e ne g le c te d . The d iffe re nc e a b o ut the p re d ic tio n o f the se ttle m e nt a na lysis b y b o th m e tho d s is a p p ro xim a te ly 10%.

Ma ny typ e s o f p ile fo r sup p o rt the silo s struc ture a re a va ila b le . Drive n a nd c a st in p la c e s p ile s a re e c o no m ic a l fo r la nd struc ture . But the g ro und he a ve a nd the vib ra tio n a sso c ia te d with the insta lla tio n c a n c a use d e sta b iliza tio n o f q ua y wa ll.

Bo re d a nd c a st in the p la c e a re the c he a p e st typ e s o f the p ile , whic h it is p o ssib le to b e c ho se n b e c a use it will ke e p the c o st o f fo und a tio n e ffic ie ntly.

The c o nstruc tio n c o st fo r the p ile fo und a tio n will b e c he a p e r tha n o the r typ e s o f fo und a tio n, b e c a use it is no t re q uire d la rg e a m o unt o f c o nc re te a nd sho rt tim e c o nstruc tio n p ro c e ss.

5. Conclusion

As the re sult o f a na lytic a l a nd num e ric a l d e sig n o f the fo und a tio n fo r sup p o rt the silo s, the re a re se ve ra l p o int tha t c a n b e c o nc lud e :

a . The p a d fo und a tio n p ro ve d to b e unsuita b le fro m a ny a sp e c ts o f fo und a tio n d e sig n, a s c a n b e e n se e n fro m the re sults o f fa c to r o f sa fe ty a g a inst fa ilure we re unsa tisfa c to ry p re d ic te d b o th b y a na lytic a l a nd num e ric a l m e tho d s. Whe re it c o uld b e c a use p la stic d e fo rm a tio n within the so il. Furthe rm o re , t will le a d to m o ve m e nt o f the fo und a tio n g re a te r tha n se ttle m e nts; in e xtre m e c a se fa ilure will o c c ur. Furthe rm o re , the p a d fo und a tio n will b e e xp e nsive struc ture d ue to re q uire d la rg e q ua ntity o f c o nc re te a nd tim e c o nsum ing . b . In the te rm s o f fa c to r o f sa fe ty the

strip fo und a tio n se e m e d to b e fe a sib le fo r the silo s. Be c a use the hig h va lue o f fa c to r o f sa fe ty p re d ic te d b y a na lytic a l m e tho d s. Ho we ve r, the se ttle m e nt is re a lly a c ritic a l p ro b le m tha t fa c e d b y strip fo und a tio n. Bo th num e ric a l a nd a na lytic a l p re d ic te d the c ritic a l va lue o f se ttle m e nt. In a d d itio n, the d iffe re nc e se ttle m e nt sho we d b y a na lytic a l m e tho d is ve ry hig h tha t it c a n c a use the c ra c k o n the to p o f fo und a tio n a nd will im p a c t

the silo ’ s struc ture . As the hig h o f the se ttle m e nt a nd the d iffe re nc e se ttle m e nt p re d ic te d in strip fo und a tio n d e sig n, it c a n b e c o nc lud e tha t the strip fo und a tio n is unre lia b le fo r the silo s. Furthe rm o re , nine silo s b uild in the ro w re q uire s la rg e o f sp a c e a lo ng the d o c ks, unfo rtuna te ly, limite d sp a c e is a p ro b le m in the site d ue to e xisting struc ture o n the site . c . Ana lytic a l a nd num e ric a l re sults

o b ta ine d p ro ve tha t the p ile fo und a tio n is c o nsid e re d to the m o st fe a sib le c ho ic e fo r sup p o rt the silo s. Furthe rm o re , the num e ric a l p re d ic tio ns sho we d a s sa m e a s a na lytic a l p re d ic tio n tha t the p ile fo und a tio n se e m s sa tisfa c to ry to sup p o rt the silo s. In the o the r ha nd , c he c king b y Euro c o d e tha t a ll the c o nd itio ns ha d b e e n sa tisfie d fo r the sa fe ty o f the struc ture . Bo re d a nd c a st in the p la c e a re the c he a p e st typ e s o f the p ile , whic h it is p o ssib le to b e c ho se n b e c a use it will ke e p the c o st o f fo und a tio n e ffic ie ntly. The c o nstruc tio n c o st fo r the p ile fo und a tio n will b e c he a p e r tha n o the r typ e s o f fo und a tio n, b e c a use it is no t re q uire d la rg e a m o unt o f c o nc re te a nd sho rt tim e c o nstruc tio n p ro c e ss.

6. References

Ang ush J. Ma c Do na ld , 1975, Wind lo a d ing o n b uild ing s, p ub lishe d b y Ap p lie d Sc ie nc e Pub lishe r LTD, 1975.

British Sta nd a rd : 8004, 1986. C o de o f p ra c tic e fo r fo unda tio n. Annua l b o o k o f British Sta nd a rd , 1986.

Burla nd , J.B, a nd Wro th, C .P. 1974.

Se ttle me nt o f b uilding a nd a sso c ia te d da ma g e . Re vie w

p a p e r, se ssio n V.611-54.

Se ttle me nt o f struc ture s. Pe nte c h p re ss. Lo nd o n Euro c o d e 7: G e o te c hnic a l De sig n

Pa rt 1: G e ne ra l Rule s (ENV 1997-1)

H. Unwin & R.A Je sse p , 2004, Lo ng te rm p ile te sting in Lo nd o n c la y: a c a se study. In:

Pro c e e ding s o f the Institute o f

c ivil e ng ine e ring , G e o e te c hnic a l

e ng ine e ring 157, Issue G E2

(2004), p p . 57-63

G .E. Ba rne s, 2000, So il Me c ha nic s: p rinc ip le a nd p ra c tic e , se c o nd e d itio n, p ub lishe d b y Pa lg ra ve Ltd .

M.B Ja ksa e t a ll, 2005, To wa rd sre lia b le a nd e ffe c tive site inve stig a tio n, G e o te c hniq ue

55, No . 2 (2005), p p . 109-121. M.J. To m linso n, 1995, Fo unda tio n

d e sig n a nd c o nstruc tio n, sixth e d itio n, p ub lishe d b y Lo ng m a n Sc ie ntific & Te c hnic a l 1995.

M. Bo zo zuk, 1976, To we r Silo Fo und a tio ns, Pub lishe d b y C a na d ia n Build ing Dig e st. O ASYS-G EO 17.9 He lp Ma nua l,

2002-2005.

Ste wa rt B.,2004-2005, Le c ture s no te s in fo unda tio n e ng ine e ring, Unive rsity o f G la sg o w.

Va n Im p e & Ha e g e m a n,1998, De e p Fo unda tio n o n Bo re d a nd Aug e r p ile s. “ La rg e dia me te r b o re d p ile s in multi-la ye re d so ils o f Ba ng ko k”. Ba lke na , Ro tte rd a m .