flow in soil

7/23/2019 flow in soil

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Chapter 1: Flow in SoilChapter 1: Flow in Soil



Table of Contents Table of Contents

1.3 Seepage analyses (Text book 8.4 – 8.1!1.3 Seepage analyses (Text book 8.4 – 8.1!

1.11.1 Capillary in soil" soil shrinkage # soil expansion

(Text book $.$ # $.1!

1.% &ea' an' ow of one an' two'i)ensional(Text book 8.% # 8.3!

1.4 Filter 'esign (Text book 8.11!1.4 Filter 'esign (Text book 8.11!



*'apte' fro) +r. ,-lies presentation sli

1.1



*'apte' fro) +r. ,-lies presentation sli



1.1 Capillarity (/ontin-e'0!1.1 Capillarity (/ontin-e'0!

Groundwater table (or phreatic surface)Groundwater table (or phreatic surface) – the leel whi/h– the leel whi/h-n'ergro-n' water will rise in an obseration well" pit or-n'ergro-n' water will rise in an obseration well" pit or

other open ex/aation in the earthother open ex/aation in the earth

Soil beneath gro-n'water table – 2lle' with waterSoil beneath gro-n'water table – 2lle' with water

Soil moistureSoil moisture

– any water in soil lo/ate' aboe the water– any water in soil lo/ate' aboe the water

tabletable

Capillary riseCapillary rise – pheno)enon whi/h water rises aboe the– pheno)enon whi/h water rises aboe the

gro-n'water table against the p-ll of graity b-t is ingro-n'water table against the p-ll of graity b-t is in

/onta/t with the water table as its so-r/e/onta/t with the water table as its so-r/e

Capillary moistureCapillary moisture – the water asso/iate' with /apillary– the water asso/iate' with /apillaryriserise

Vadose zoneVadose zone – the soil region 'ire/tly aboe the water– the soil region 'ire/tly aboe the water

table an' wette' by /apillary )oist-retable an' wette' by /apillary )oist-re



ater in Capillary T-besater in Capillary T-bes

asi/ prin/iples of /apillary rise in soils relate'asi/ prin/iples of /apillary rise in soils relate'to the rise of water in glass /apillary t-besto the rise of water in glass /apillary t-bes

The rise – attra/tion The rise – attra/tion

between the waterbetween the water

an'an'

the glass an' to athe glass an' to a

s-rfa/e tension Ts-rfa/e tension Tss

whi/hwhi/h

'eelops at the air5'eelops at the air5waterwater

interfa/e at the top ofinterfa/e at the top of

the water /ol-)n inthe water /ol-)n in

thethe

/apillary t-be/apillary t-be



ater in Capillary T-bes (/ontin-e'0!ater in Capillary T-bes (/ontin-e'0!

6al-e of T6al-e of Tss for water aries a//or'ing tofor water aries a//or'ing tote)perat-rete)perat-re

*s te)perat-re in/reases" the al-e of T*s te)perat-re in/reases" the al-e of Tss 'e/reases" in'i/ating a lessening height of'e/reases" in'i/ating a lessening height of

/apillary rise -n'er war) /on'itions/apillary rise -n'er war) /on'itions *t roo) te)perat-re" T*t roo) te)perat-re" Tss for water 7 .4 9)for water 7 .4 9) *t free;ing" T*t free;ing" Tss for water 7 .< 9)for water 7 .< 9)

(=proi'e' that ' is in )illi)etres!(=proi'e' that ' is in )illi)etres!




>n applying the 'eelop)ent of /apillary risein t-bes to /apillary rise in soils:h/ ? 31' )) (@/Carthy" +. F." %%!

(=proi'e' that ' is in )illi)etres!




A-estion:A-estion:

Co)p-te the height of /apillary rise for water in aCo)p-te the height of /apillary rise for water in at-be haing a 'ia)eter of .B )) (in S> -nits!t-be haing a 'ia)eter of .B )) (in S> -nits!

Sol-tion:Sol-tion:

mmkN m x

m N

d

T h

w

s

c 52.0

)/81.9)(105(

)/064.0)(4(435

===−

γ




The height of /apillary rise is not ae/te' by a slope or The height of /apillary rise is not ae/te' by a slope orin/lination in the 'ire/tion of the /apillary t-be" or byin/lination in the 'ire/tion of the /apillary t-be" or by

ariations in the shape an' si;e of the t-be at leel below theariations in the shape an' si;e of the t-be at leel below the

)enis/-s)enis/-s




Capillary rise is not li)ite' to t-be" or en/lose'" shapes. >f twoCapillary rise is not li)ite' to t-be" or en/lose'" shapes. >f twoerti/al glass plates are pla/e' so that they to-/h along one en'erti/al glass plates are pla/e' so that they to-/h along one en'

an'" for) a 6" a we'ge of water will rise -p in the 6 be/a-se ofan'" for) a 6" a we'ge of water will rise -p in the 6 be/a-se of

the /apillary pheno)enonthe /apillary pheno)enon



Capillary rise in soilCapillary rise in soil

Shapes of oi' spa/es between soli' parti/les are -nlike those in /apillary t-besShapes of oi' spa/es between soli' parti/les are -nlike those in /apillary t-bes 6oi's are of irreg-lar an' arying shape an' si;e" an' inter/onne/t in all 'ire/tions" not only the erti/al6oi's are of irreg-lar an' arying shape an' si;e" an' inter/onne/t in all 'ire/tions" not only the erti/al

The feat-res of /apillary rise in t-bes are appli/able to soils in so far as they fa/ilitate an -n'erstan'ing The feat-res of /apillary rise in t-bes are appli/able to soils in so far as they fa/ilitate an -n'erstan'ing

of fa/tors ae/ting /apillarity" an' help to establish an or'er of )agnit-'e for /apillary rise in theof fa/tors ae/ting /apillarity" an' help to establish an or'er of )agnit-'e for /apillary rise in the

'ierent types of soils'ierent types of soils



Capillary rise in soil (/ontin-e'0.!Capillary rise in soil (/ontin-e'0.!

A-estion:A-estion:

,i)ite' laboratory st-'ies in'i/ate that for a /ertain silt,i)ite' laboratory st-'ies in'i/ate that for a /ertain silt

soil" the ee/tie pore si;e for height of /apillary rise issoil" the ee/tie pore si;e for height of /apillary rise is

1B of +1B of +11" where +" where +11 is the 1 per/ent parti/le si;e fro)is the 1 per/ent parti/le si;e fro)

the grain5si;e 'istrib-tion /-re. >f the +the grain5si;e 'istrib-tion /-re. >f the +11 si;e for s-/h asi;e for s-/h a

soil is .%))" esti)ate the height of /apillary rise.soil is .%))" esti)ate the height of /apillary rise.

Sol-tion:Sol-tion:

' 7 ee/tie /apillary 'ia)eter 7 1B+' 7 ee/tie /apillary 'ia)eter 7 1B+11 7 1B (.% ))!7 1B (.% ))!

7 .4 ))7 .4 ))

hh// ≅≅ 31'31' ≅≅ 31.4 ))31.4 )) ≅≅ <<B ))<<B )) ≅≅ <.<B)<.<B)




Capillary fringe




Soil TypeSoil Type MeterMeter

(m)(m)

S)all graelS)all grael .%5.1.%5.1

Coarse san'Coarse san' .1B.1B

Fine san'Fine san' .3 to 1.3 to 1SiltSilt 1 to 11 to 1

ClayClay 1 to 31 to 3

Table : Depresentatie heights of /apillary rise: Table : Depresentatie heights of /apillary rise:

water in soilwater in soil

S il h i k # ilS il h i k # il



Soil shrinkage # soilSoil shrinkage # soil

swellingswelling Soil -n'ergo a ol-)e /hange when the water /ontent is /hange'.Soil -n'ergo a ol-)e /hange when the water /ontent is /hange'.

+e/rease in water /ontent /a-se shrinkage.+e/rease in water /ontent /a-se shrinkage.

>n/rease of water /ontent /a-se swelling.>n/rease of water /ontent /a-se swelling.

SHRINKAGE OF SOILSSHRINKAGE OF SOILS

hen sat-rate' soils is allowe' to 'ry" a )enis/-s 'eelops in ea/h oi' athen sat-rate' soils is allowe' to 'ry" a )enis/-s 'eelops in ea/h oi' at

the soil s-rfa/e.the soil s-rfa/e.

For)ation of s-/h a )enis/-s /a-ses tension in the soil water lea'ing to aFor)ation of s-/h a )enis/-s /a-ses tension in the soil water lea'ing to a/o)pression in the soil str-/t-re an' /onseE-ent re'-/tion in the ol-)e./o)pression in the soil str-/t-re an' /onseE-ent re'-/tion in the ol-)e.

hen the )enis/-s attains its )ini)-) al-e" /o)pressie for/es arehen the )enis/-s attains its )ini)-) al-e" /o)pressie for/es are

)axi)-) an' shrinkage is also )axi)-).)axi)-) an' shrinkage is also )axi)-).



Soil shrinkage # soilSoil shrinkage # soil

swellingswellingSWELLING OF SOILSSWELLING OF SOILS

hen water is a''e' to a soil whi/h has shr-nk" )enis/-s arehen water is a''e' to a soil whi/h has shr-nk" )enis/-s are

'estroye' res-lting in tension in the pore water an''estroye' res-lting in tension in the pore water an'

/onseE-ent re'-/tion in /o)pressie stresses in soli' grains./onseE-ent re'-/tion in /o)pressie stresses in soli' grains.

This res-lt in elasti/ expansion of the soil )ass" /a-sing This res-lt in elasti/ expansion of the soil )ass" /a-singswelling.swelling.

>n /lay soils" swelling is /a-se' )ainly '-e to rep-lsie for/es>n /lay soils" swelling is /a-se' )ainly '-e to rep-lsie for/es

whi/h separate the /lay parti/les" /a-sing ol-)e /hange.whi/h separate the /lay parti/les" /a-sing ol-)e /hange.



1.%1.% &ea' an' ow of one an' two

'i)ensional ne5 'i)ensional ow – the elo/ity atne5 'i)ensional ow – the elo/ity at

all points has the sa)e 'ire/tion an'all points has the sa)e 'ire/tion an'

(for an in/o)pressible -i'! the sa)e(for an in/o)pressible -i'! the sa)e)agnit-'e)agnit-'e

Two5'i)ensional ow – all strea)lines Two5'i)ensional ow – all strea)lines

in the ow are plane /-res an' arein the ow are plane /-res an' are

i'enti/al in a series of parallel planesi'enti/al in a series of parallel planes



1.%1.% &ea' an' ow of one an'two

'i)ensional (/ontin-e'0!

Defer to Gage %43" 8.% in yo-r +*S"

ook.

9otes:+is/harge elo/ity" v = ki

k = hydraulic conductivity

i = hydraulic gradient (i = h!") h = head loss



1.3 Seepage analyses1.3 Seepage analyses



1.3 *nalysis of ow nets an'1.3 *nalysis of ow nets an'

seepageseepage

@any /atastrophi/ fail-res in@any /atastrophi/ fail-res ingeote/hni/al engineering res-lt fro)geote/hni/al engineering res-lt fro)

instabilityinstability of soil )assesof soil )asses '-e to gro-n''-e to gro-n'

water owwater ow

,ies are lost" infrastr-/t-res are,ies are lost" infrastr-/t-res are

'a)age' or 'estroye'" an' )aHor'a)age' or 'estroye'" an' )aHor

e/ono)i/ losses o//-rre'e/ono)i/ losses o//-rre'

>n this s-b/hapter" yo- will st-'y the>n this s-b/hapter" yo- will st-'y thebasi/ prin/iples of two5'i)ensional owbasi/ prin/iples of two5'i)ensional ow

of water thro-gh soilsof water thro-gh soils




seepageseepage (/ontin-e'0! (/ontin-e'0! The topi/s that yo- will st-'y wo-l' The topi/s that yo- will st-'y wo-l'

help yo- tohelp yo- to aoi' pitfallsaoi' pitfalls in thein the

analyses an' 'esign of geote/hni/alanalyses an' 'esign of geote/hni/al

syste)s where ow of gro-n' watersyste)s where ow of gro-n' water/an lea' to instability/an lea' to instability

The e)phasis of this /hapter is on The e)phasis of this /hapter is on

gaining angaining an -n'erstan'ing of the for/es-n'erstan'ing of the for/es that prooke fail-res fro) ow ofthat prooke fail-res fro) ow of

gro-n' watergro-n' water




seepageseepage (/ontin-e'0! (/ontin-e'0!Learnin O!"e#ti$e%&Learnin O!"e#ti$e%& In'erstan' theIn'erstan' the basi/ prin/iplesbasi/ prin/iples of two5of two5

'i)ensional ow'i)ensional ow

e able toe able to /al/-late/al/-late seepage stresses"seepage stresses"pore5water press-re 'istrib-tion" -pliftpore5water press-re 'istrib-tion" -pliftfor/es" hy'ra-li/ gra'ients" /riti/alfor/es" hy'ra-li/ gra'ients" /riti/alhy'ra-li/ gra'ient" ow -n'er an' withinhy'ra-li/ gra'ient" ow -n'er an' withinearth str-/t-researth str-/t-res

e able toe able to 'eter)ine the stability'eter)ine the stability ofofgeote/hni/al syste)s s-bHe/te' to two5geote/hni/al syste)s s-bHe/te' to two5'i)ensional ow of water'i)ensional ow of water



1.3.1 asi/ Con/epts1.3.1 asi/ Con/epts

The two5'i)ensional ow of water thro-gh soils is The two5'i)ensional ow of water thro-gh soils is

goerne' by ,apla/es eE-ation. The pop-lar for)goerne' by ,apla/es eE-ation. The pop-lar for)of ,apla/es eE-ation for two5'i)ensional ow ofof ,apla/es eE-ation for two5'i)ensional ow ofwater thro-gh soils iswater thro-gh soils is

here khere kxx an' kan' k;; are the /oeJ/ient of per)eabilityare the /oeJ/ient of per)eabilityin the x an' ; 'ire/tions an' & is the hea'in the x an' ; 'ire/tions an' & is the hea'

The ass-)ptions in ,apla/es eE-ation are: The ass-)ptions in ,apla/es eE-ation are:

(i! +ar/ys law is ali'" 7 ki(i! +ar/ys law is ali'" 7 ki (ii! The soil is ho)ogeneo-s an' sat-rate'(ii! The soil is ho)ogeneo-s an' sat-rate'

(iii! The soil an' water are in/o)pressible(iii! The soil an' water are in/o)pressible

(i! 9o ol-)e /hange o//-rs(i! 9o ol-)e /hange o//-rs

02

2

2

2

=∂

∂+

∂

∂

z

H k

x

H k

z x



1.3.1 asi/ Con/epts1.3.1 asi/ Con/epts

(/ontin-e'0!(/ontin-e'0! >f the soil were an isotropi/ )aterial then k>f the soil were an isotropi/ )aterial then kxx 7 k7 k;;

an' ,apla/es eE-ation be/o)es:an' ,apla/es eE-ation be/o)es:

The sol-tion of ,apla/es eE-ation reE-ires The sol-tion of ,apla/es eE-ation reE-iresknowle'ge of the bo-n'ary /on'itions.knowle'ge of the bo-n'ary /on'itions.

Co))on geote/hni/al proble)s hae /o)plexCo))on geote/hni/al proble)s hae /o)plexbo-n'ary /on'itions fro) whi/h it is 'iJ/-lt tobo-n'ary /on'itions fro) whi/h it is 'iJ/-lt to

obtain a /lose' for) sol-tion.obtain a /lose' for) sol-tion. *pproxi)ate )etho's s-/h as graphi/al )etho's*pproxi)ate )etho's s-/h as graphi/al )etho's

an' n-)eri/al )etho's are often e)ploye'.an' n-)eri/al )etho's are often e)ploye'. >n this s-b/hapter" graphi/al )etho'" /alle' the>n this s-b/hapter" graphi/al )etho'" /alle' the

ow net te/hniE-e or ow net sket/hing" thatow net te/hniE-e or ow net sket/hing" that

satis2es ,apla/es eE-ation is 'is/-sse'.satis2es ,apla/es eE-ation is 'is/-sse'.

02

2

2

2

=∂

∂+

∂

∂

z

H

x

H



'. * 1+,-



9o of eE-ipotential'rops at point a

Kleation loss



hpγ w



Iplift for/esIplift for/es

Stati/ ,iE-efa/tion &eaing oiling #Stati/ ,iE-efa/tion &eaing oiling #



Stati/ ,iE-efa/tion" &eaing" oiling" #Stati/ ,iE-efa/tion" &eaing" oiling" #

GipingGiping

Static li#uefactionStatic li#uefaction – the state whi/h the ee/tie stress– the state whi/h the ee/tie stress

be/o)es ;ero" the soil loses its strength an' behaes like abe/o)es ;ero" the soil loses its strength an' behaes like ais/o-s -i'is/o-s -i' oiling" E-i/ksan'" piping an' heaing are -se' to 'es/ribeoiling" E-i/ksan'" piping an' heaing are -se' to 'es/ribe

spe/i2/ eents /onne/te' to the stati/ liE-efa/tion statespe/i2/ eents /onne/te' to the stati/ liE-efa/tion state $oiling$oiling – the -pwar' seepage for/e ex/ee's the 'ownloa'– the -pwar' seepage for/e ex/ee's the 'ownloa'

for/e of the soilfor/e of the soil %iping%iping – the s-bs-rfa/e Lpipe5shape'M erosion that initiates– the s-bs-rfa/e Lpipe5shape'M erosion that initiates

near the toe of 'a)s an' si)ilar str-/t-res. &igh lo/ali;e'near the toe of 'a)s an' si)ilar str-/t-res. &igh lo/ali;e'hy'ra-li/ gra'ient stati/ally liE-e2es the soil" whi/hhy'ra-li/ gra'ient stati/ally liE-e2es the soil" whi/hprogresses to the water s-rfa/e in the for) of a pipe" an'progresses to the water s-rfa/e in the for) of a pipe" an'water then r-shes beneath the str-/t-re thro-gh the pipe"water then r-shes beneath the str-/t-re thro-gh the pipe"lea'ing to instability an' fail-relea'ing to instability an' fail-re

&uicksand&uicksand – existen/e of a )ass of san' in a state of stati/– existen/e of a )ass of san' in a state of stati/liE-efa/tionliE-efa/tion

,iE-efa/tion – /an be pro'-/e' by 'yna)i/ eents s-/h as,iE-efa/tion – /an be pro'-/e' by 'yna)i/ eents s-/h asearthE-akesearthE-akes



GipingGiping

i i ( i ' !Gi i ( ti ' !



Giping (/ontin-e'0!Giping (/ontin-e'0!

The risk of piping /an o//-r in seeral The risk of piping /an o//-r in seeral/ir/-)stan/es" s-/h as a /oer'a) (a! or/ir/-)stan/es" s-/h as a /oer'a) (a! orthe 'ownstrea) en' of a 'a) (b!the 'ownstrea) en' of a 'a) (b!

>n or'er to in/rease the fa/tor of safety>n or'er to in/rease the fa/tor of safetyagainst piping in these /ases two )etho'sagainst piping in these /ases two )etho's/an be a'opte'/an be a'opte'

(1! in/rease the 'epth of pile penetration in(1! in/rease the 'epth of pile penetration in(a! an' inserting a sheet pile at the heel of(a! an' inserting a sheet pile at the heel ofthe 'a) in (b!N in either /ase there is anthe 'a) in (b!N in either /ase there is anin/rease in the length of the ow path ofin/rease in the length of the ow path ofthe water with a res-lting 'rop in thethe water with a res-lting 'rop in theex/ess press-re at the /riti/al se/tion.ex/ess press-re at the /riti/al se/tion.

Gi i ( i ' !Gi i ( ti ' !



Giping (/ontin-e'0!Giping (/ontin-e'0!

* si)ilar ee/t is a/hiee' by laying* si)ilar ee/t is a/hiee' by laying'own a blanket of i)per)eable'own a blanket of i)per)eable

)aterial for so)e length along the)aterial for so)e length along the

-pstrea) gro-n' s-rfa/e-pstrea) gro-n' s-rfa/e

(%! To pla/e a s-r/harge or 2lter apron(%! To pla/e a s-r/harge or 2lter apron

on top of the 'ownstrea) si'e" theon top of the 'ownstrea) si'e" the

weight of whi/h in/reases theweight of whi/h in/reases the

'ownwar' for/es'ownwar' for/es

Kxa)ple:5Kxa)ple:5



Kxa)ple:Kxa)ple:



thers pheno)enon: A-i/kthers pheno)enon: A-i/k

san'" Frost heae in soils"san'" Frost heae in soils"

liE-efa/tionliE-efa/tion

A i k 'A i k '



A-i/ksan'A-i/ksan'

+rea'e' E-i/ksan' /on'ition o//-rs where+rea'e' E-i/ksan' /on'ition o//-rs wherea san' or /ohesionless silt 'eposit isa san' or /ohesionless silt 'eposit iss-bHe/te' to the seepage for/e /a-se' bys-bHe/te' to the seepage for/e /a-se' by-pwar' ow of gro-n'water-pwar' ow of gro-n'water

The -pwar' gra'ient of the water is The -pwar' gra'ient of the water iss-J/ient to hol' the soil parti/les ins-J/ient to hol' the soil parti/les ins-spension" in ee/t /reating a )aterials-spension" in ee/t /reating a )aterialwith the properties of a heay liE-i'with the properties of a heay liE-i'

Kli)ination of seepage press-re will ret-rnKli)ination of seepage press-re will ret-rnthe soil to a nor)al /on'ition /apable ofthe soil to a nor)al /on'ition /apable ofproi'ing s-pportproi'ing s-pport

Frost heae in soilsFrost heae in soils



Frost heae in soilsFrost heae in soils hen free;ing te)perat-res 'eelop in a soil )ass" )ost of thehen free;ing te)perat-res 'eelop in a soil )ass" )ost of the

pore water in the soil is also s-bHe/t to free;ing. *s waterpore water in the soil is also s-bHe/t to free;ing. *s water

/ystalli;es" its ol-)e expan's approxi)ately $ per/ent/ystalli;es" its ol-)e expan's approxi)ately $ per/ent >n /onsi'ering oi' ratios an' the 'egree of sat-ration for soils">n /onsi'ering oi' ratios an' the 'egree of sat-ration for soils"

expansion of a soil )aterial as a res-lt of free;ing )ight beexpansion of a soil )aterial as a res-lt of free;ing )ight beexpe/te' to be on the or'er of 3 or 4 per/ent of the original ol-)eexpe/te' to be on the or'er of 3 or 4 per/ent of the original ol-)e

Frost eae n so sros eae n so s



(/ontin-e'00!(/ontin-e'00! >n the nor)al frost heae o//-rren/e" the so-r/e of water is the>n the nor)al frost heae o//-rren/e" the so-r/e of water is the

gro-n'water tablegro-n'water table Ipwar' )oe)ent fro) a water table to the free;ing ;oneIpwar' )oe)ent fro) a water table to the free;ing ;one

relates to a potential for )igration (/apillary rise!relates to a potential for )igration (/apillary rise! &eight of /apillary rise is E-ite li)ite' in /lean" /oarse5graine'&eight of /apillary rise is E-ite li)ite' in /lean" /oarse5graine'

soilsoil



Soil liE-efa/tionSoil liE-efa/tion• * pheno)enon in whi/h the strength an' stiness

of a soil is re'-/e' by earthE-ake shaking or rapi'loa'ing.

• //-rs in sat-rate' soils.•

The water exerts a press-re on the soil parti/lesthat in-en/es how tightly the parti/le the)selesare presse' together.

• Grior to an earthE-ake" the water press-re isrelatiely low.

• KarthE-ake shaking /an /a-se the water press-reto in/rease to the point where the soil parti/le /anrea'ily )oe with respe/t to ea/h other.



1.4 Filter 'esign1.4 Filter 'esign

Text book se/: 8.11



Kn' of Chapter 1Kn' of Chapter 1

flow in soil

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