1Khi nim v

C

hc t khng bo ha v

plaxflow

GS. Nguyn Cng Mn

PLAXIS FINITE ELEMENT CODES

2Kn v H t bo ho/khng bo ho

LT. Chiu cao

i

BH MD Ct ht th: h rt nh t bi: h c th

t 2m t st: h c th

t trn 20m

S ht t Bn knh mt khum

0,0002 cm

0,002 cm

0,02 cm

Theo th nghim cao

dng mao dn ng vicc ng knh mt khum

khc nhau(Janssen & Dempsey, 1980)

TH p

ti khng bo ho

Khng

BH: uw

v ua

Kh: u = 0

Bo ho MD: uw

< 0

Bo ho: uw

> 0

+u

-u

u = w

.h w

+h

-h

(1)

(2)

(3)

(4)

Vk

kh

Vn

nc

Vh

rn

Vr

V

Kssat

VVn=

Kresidu

-u

+u

3Khi nim

v

C hc t khng

boho

ng

sut

c

hiu

qu

- uw

p lc

nc l rng

dng

LT .S c hiu qu Terzaghi

Fredlund

ht

dnhng

sut

php thc

- uw ua

- uw

4Cu

trc

thnh

phn

ca

t

khng

bo ho

Vk

0

Vn

0

Vh

0

Vm

0 S

l thuyt

KBH

kh

nc

rn

mt

cng

t

bo ho(BH)

t

bo ho ch cha

ht rn v nc: mi trng

2 pha;

L

rng

cha

y

nc;

bo ho: Vn

/Vr

= 1;

cha

nc

th tch: w

= Vn

/V

=

Vr/V = n

rng

(n): n = Vr

/V;

Vn

= Vr

Vh

t

BH

V

Vr

th

tch

rng

ca phn t

t V

tng

th

tch

ca phn t

t t

khng

bo ho (KBH)

t

khng

bo ho cha

ht rn, kh

v nc: mi trng

3 pha;

L

rng

cha

c kh

v nc;

bo ho: Vn

/Vr

< 1;

cha

nc

th

tch: w

= Vn

/V

w < n

rng

(n): n = Vr

/V;

t

khng

BH

Vk

kh

Vn

nc

Vh

rn

Vr

5MH dng

thm

trong

t

khng

bo ho

Tc ng

pha

kh:

Gim vn

tc

thm;

Mt

phn cch

Nc

-

Kh

To

sc

cng mt ngoi

trong h.

Pha

th

4.

SS

= 1= 1 1 > S > 1 > S > SSresiduresidu S = S = SSresiduresidu

Theo S. Lee Barbour, H Saskatchewan

S

-

bo ho

; Sresidu

-

bo ho d

Kh Kh

bo ha hiu qua theo V.Genuchten

1=

residusat

residue SS

SSS

K

Kssat

VVn=Sresidu

Ssat

S

6nh

hng

ca pha

kh

-

Khi

trng thi khng

bo ho, t

l mt h

4 pha: ht t, nc, kh

v mt ngoi cng,

ng

thi tn

ti trong l rng

ca

t;

-

S tn

ti ca bt kh

lm gim tnh thm

ca

t bt kh

cng nhiu, lng cha

nc

cng t, th

tnh thm

cng nh

v ngc

li. Lun tn ti mt lng nc trong l rng do kh kn nht li

bo ha d

(Residual saturation) [V.Genuchten]

-

Mt ngoi cng

ti mt

phn cch kh

-

nc

to nn lc ht gia cc ht t, gi

l lc ht dnh

( matric

suction ) hay p lc l rng

m.

7tn

ti ca mt

ngoi cng v

s

cc lc

mao

dn

tc dng

ln ng

mao

dn

Nh c lc

cng b mt, nhn

nc khng tt vo nc, b

bi nga khng bt khi mt

nc

Cc cn trng

sng

trn v di

mt

ngoi cngL.J. Milne

& M. Milne

( 1978 )

Nhn

nc

Cn trng

bi nga

Mt

nc

S cc lc

tc dng ln ng

mao

dn

Ts

-

lc

cng

b

mt

ca

ncRs

-

bn knh

cong ca mt

khum

n

g

s

u

t

n

n

l

n

t

h

n

h

n

g

n

g

s

u

t

n

n

l

n

t

h

n

h

n

g

( )s

swa R

Tuu 2=

khng

kh

Ts Ts

ng

thu

tinhmao dn

nc

8lc

ht

dnh

v

lc

cng mao dn

iu kin

cn bng:

Tst

-

trng

lng

ct

nc

hc

hay2.r.Ts

.cos

= .r2

w.

g.hcw

.g. hc

= 2Ts

/Rs hc

= 2Ts

/w

.g. Rs

hc

1/r

Tst

=Ts

.cos

; Rs

= r/cos

iu kin

binua

(C) =

0

uw

(B) = uw

(A) = 0uw

(C) = -

w

.g. hcua

(c) -

uw

(c) = w

.g. hc

= 2Ts

/Rs

matric

= ua

- uw

lc

ht

dnh

ng thu

tinh

mao

dn

p sut

kh

quynua

= 0Mt

khum

uw

(A) = uw

(B) = 0

Phn b

p sutnc

hc

-(-)

(+)Mt nc

B

Ts

Rs

Tst

Ts

Cw2r

A

9

bn

chng

ct do lc

ht

dnh

to nn

( )s

swamatric

R

T2uu ==

bmatricmatric tan. =

( )wamatric uu =Thnh

phn

lc

ht

dnh

ny rt

quan

trng

trong

c hc

t

khng

bo ho,

n

gp

phn

m

rng

pht trin

nguyn l

ng

sut

c

hiu

qu ca

Terzaghi

trong

CH

c

in

cho

t

bo

ho. N

nh

hng

ln

n

tnh

thm

v

chng

ct ca

t.

p sut tip xc

matricmatricLc

ht

mao

dn

Ts

ht t

Tsht t

Nguyn

Cng

Mn, 1999

10

Cc bin

trng ng

sut

trong

t

KBH

Y

X

Z

y - ua

z - ua

ua - uw

ua - uw x - uaua - uwxz

xy

yxyz

zxzy

(x - ua )

xz

(y - ua)(z- ua )

xy yz

yx zx zy

Tens ng

sut

(ua- uw )

0

0

0

0 0

0

(ua- uw )

(ua- uw )

Tens cu

ng

sut p sut t pha

11

Mt

s

nh

ngha

c

Bn Design Standard -

Embankment Dams Chapt. 8 -

Seepage Analysis & Control-1987

Saturated Flow ( SF ): Dng

chay

trong

MT rng

ti

vng

c

AL l

rng

dng

pha

di

ng

mt

thong

-

dc

theo

, AL l

rng

= AL kh

quyn. SF

ch

y

gy ra

bi

gradien

TL trng

lc;

Unsaturated Flow ( UF ): Dng

chay

trong

MT rng

ti vng

c

AL l

rng

m

pha

trn

ng

mt

thong. UF ch

yu

gy ra

bi

gradien

TL

do

chnh

sc

cang b

mt;

AL l

rng

( ALLR ): AL nc

trong

cc l

rng

lin

thng

thuc

vt

liu

thn hay nn

CT v

bao

gm

:

AL nc

LR dng

to ra

do trng

lc

v

AL LR m

( Matric

Suction

) to ra

bi

sc

cang b

mt.

12

bn

chng

ct theo

ht

dnh Pht trin

nguyn l

SHQ Terzaghi

PP th

nghim

vnthc

hin

nh thng

l: UU, CD, CU.

wu au

= c + ( - ua

) tan + (ua

- uw

) tanb

c(u a

- uw

)

b

(

- ua

)c( - ua

) tan

(ua

- uw

) tanb

c

Xc nh

bng thit b

TN ct trc tiphoc nn ba trcthng thng, cci tin

o cring r

-

c lp

13

ng

cong c trng

Nc

-

t TRONG VNG KHNG BO HO

m

d

hay

bo ho

d:

bo ho

thp nht khi

nc

trong

cc

l

rng khng lin

thng

Gi tr

kh

vo ti

hn: ht

dnh

ng

vi

lc

kh

c

th thm

vo cc l

rng

ln

nht

Quan

h

m

th tch lc ht dnh

V

Gi tri kh

vo ti

hn -

th

Vn

VVn=

Khng bo ho

Lc ht dnh0

r (

Sr

) -

m

d

Bo ho

=

mw uw

bh

= nmv

SS

= 1= 1

1 > S > 1 > S > SSrr

S = S = SSrr

mwuw

VVr

r =

14

Dng ca SWCC ph

thuc phn b

c

l

rng trong t

ng cong c trng nc -

t

SWCC TRONG VNG KHNG BO HO

C v phn b c ht

Cu trc ca t

Bin thin th tch (h s rng)

Hysteresis

Nhn t nh hng n SWCC

t ht mn, cp phi tt

Suction (kPa)

qw

t ht th, ng u

Suction (kPa)

qw

15

ng

cong Nc -

t

khi qut ho

th

-

hm ca c

l

rng

max

trong

t, bin i

do s

phn

b

c

l

rng;d

-

ng

vi lc

nc

cha

trong

cc l rng khng lin thng.

B

100

80

60

40

20

0

0.1 1 100 10.000 1.000.000

ht

ca

t

( suction ) ( kPa

)

m

t

h

t

c

h

(

%

)

Gi tr

kh

vo ti

hn th

m

d d-

A

16

ng

cong c

trng

t -

Nc v Hm thm trong vng khng bo ho

ng

cong c

trng

t -

Nc (SWCC)- M t

lng

cha

nc

trong

t

theo

lc ht dnh

-

Dng ng

cong c

quan

h

vi

ln v

phn b

kch

c

l

rng, ....

Hm thm- M t

bin thin h

s

thm

theo

lc ht dnh;

- Phn nh

bn cht

v

c

dng ca

SWCC;

Xc nh

hm thm

- D tnh t ng

cong SWCC v

biu

thc

GT;-

o bng

bung

p lc

( TEMPE -

Soil moisture

Equip. Corp.in Santa Barbara, Calif.USA ).

17

Hm

thm

trong vng khng bo ho

SEEP/W. 5

PP Green & Corey, Fredlund & Xing v MH Van Genuchten. PLAXIS V. Genuchten

C th d tnh hm thm t

ng

cong c trng nc -

t

= f (uw

) K = g ()K = h (uw

)

t bo hok = constant

S = 1

bo ho t khng

k = f [ S, , (ua uw)]

S < 1

H

s

t

h

m

(

t

h

a

n

g

l

o

g

1

0

)

Gi tri kh

vo ti

hn -

thk

ht dnh0

18

MH Hm

thm

trong vng khng bo hoTheo van Genuchten

LT & thc o

w

wu =

Ch

: PlaxFlow

ch

dng hm thm

trong vng khng bo ho

phn

tch thm.

19

( )( ) 1 n( )n nres sat res a( ) 1 gg gpS S S S g h = + +

Sresidu

:

bo ho tng dga

, gn

v gl

: cc thng s khp ng cong (curve

fitting parameters)

MH Hm

thm

trong vng khng bo hoTheo van Genuchten

Rt ra: =

krel

0

1

p pk( ) ( )

21

111

=

n

n

n

nl

gg

gg

eg

erelative SSSkV:

20

MH Hm

thm

trong vng khng bo hoTheo van Genuchten

H

S

tng d

Storage CoefficientH

s

tng trTng t

mw trongSEEP/W

w

wu =

K () permeability curve

( )k kSoil Permeability =

() Soil water characteristic curve( )sCStorage Coefficient

=

w

ww u

um = )(

)(

21

MH hm thm V.Genuchten

v

d

QH

bo ha -

ct p

b

o

h

a

(

-

)

Ct -

Ssat =1; Sresidu = 0,027ga = 2,24; gl

= o;gn

= 2,286

Ct p (m) Ct p (m)

Ct -

Ssat =1; Sresidu = 0,027ga = 2,24; gl

= o;gn = 2,286

QH HS thm t

-

ct p(relative permeability)

H

-

S

t

h

m

t

n

g

i

(

-

)

M

hinh l

thuyt

M

hinh xp x

H

-

S

t

h

m

t

n

g

i

(

-

)

Ct p (m)

QH HS thm t

-

ct p (relative permeability)

pk

= 1,15

Ct p (m)

b

o

h

a

(

-

)

QH

bo ha -

ct p

ps

= 1,48

22

MH l

thuyt van Genuchten

23

So snh gia PlaxFlow

v

SEEP/W

QH HS thm t

-

ct p

H

S

t

h

m

t

n

g

i

(

-

)

Ct p (m)

1,0

-1,0

0,5

-0,5 0

QH K

-

ht dnh

QH

-

ht dnh

SEEP/W

QH

bo ha t

-

ct p

b

o

h

a

t

n

g

i

(

-

)

Ct p (m)

PLAXFLOW

1,0

-1,0

0,5

-0,5 0

1=

residusat

residue SS

SSS

24

MH hm thm V.Genuchten tuyn tnh ha theo PlaxFlow cc thng s

xp x

Quan h

tuyn tnh

bo ho

S(p ) trong vng khng bo ho

ps

-

ct p xc nh vng khng bo ha trong k thy tnh, di gi

tr

ngng ny, GT S(p ) = 0.

pk

ct p xc nh vng khng bo ha trong k thy tnh, di gi

tr

ngng ny, GT krel

(pk

) = 10-4

QH log-tuyn tnh HS thm tkrelative

(p

) trong vng khng BH

krelKrel

(pk

) = 10-4

0

1

p pkm

25

MH sp x

van Genuchten

26

Quan h HS thm

kch thc c htKch thc c

ht d10

c

quan h

cht ch

vi HS thm

10-6

and lessClay5x10-3

10-5Silt

2x10-3

10-4Silty sand5x10-2

10-3Fine sand

10-2

5x10-3Sand mixture

1

10-2Clean sand (coarse)

> 1Clean gravel

k (cm/s)Soil

Harr (1962)

minmax

max

eeeeDr

=

[ng knh hiu qu

D10, mm]

Ch

thch:

Tung

-

HS thm, K (cm/s) c

cht tng i Dr = 40%;Honh

-

ng knh hiu qu

D10, mm.

27

Phn loi t theo PP tam gic Feret

C

hc t, 1970

L.Q.An, N.C. Mn, N.V. Qu. NXB H v

THCN

H

28

HYPRES l

h

PL t quc t

c lp theo mt d

n do EU ti tr. PlaxFlow

dng b

d

liu ny suy ra cc thng s

thu

lc

m

hinh ho

cc NC v

mi trng v

quy hoch s

dng t

[Hydraulic Properties of European Soil]

Phn loi t theo h

HYPRES

1m = 10-4mm

29

La chn thng s

thu

lc theo h

HYPRES

30

Ba nhm d

liu phn loi t

Staring:H phn li t ca H lan

Dutch

Standard: Hypres

dng cho MH sp x van

Genuchten ti vng khng bo ho

USDA:

United State Department of Agriculture

-

31

Slide Number 1Slide Number 2Slide Number 3Slide Number 4MH dng thm trong t khng bo honh hng ca pha khtn ti ca mt ngoi cng v s cc lc mao dn tc dng ln ng mao dn lc ht dnh v lc cng mao dn bn chng ct do lc ht dnh to nnCc bin trng ng sut trong t KBHMt s nh ngha c BnDesign Standard - Embankment Dams Chapt. 8 - Seepage Analysis & Control-1987 bn chng ct theo ht dnhPht trin nguyn l SHQ Terzaghing cong c trng Nc - tTRONG VNG KHNG BO HO ng cong c trng nc - t SWCC TRONG VNG KHNG BO HO ng cong Nc - t khi qut hong cong c trng t - Nc v Hm thm trong vng khng bo ho Slide Number 17Slide Number 18Slide Number 19Slide Number 20Slide Number 21Slide Number 22Slide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Ba nhm d liu phn loi tSlide Number 31