Coloane AA - profil T - Liu PPT.pdf

8/10/2019 Coloane AA - profil T - Liu PPT.pdf

1/33

LiuSongyu

Prof

.Dr.

InstituteofG

eotechnicalEn

gineering,

SoutheastUniversity,Nanjing,China

TheT-shaped

deepmix

edcolumn

applicationinsoftground

improvement

4th

inte

rnationalconferen

ceonGroutingand

DeepMixing

New

Orleans,Feb.1

8,2

012


2/33

Background

Fieldtest

Resultsand

analysis

Application

s

Conclusions

Outlineofth

epresen

tation


3/33


4/33

Twoeng

ineering

problems:Softsoil

groundan

dseismic

liquefactio

n


5/33

B

ackground

Soil-ce

mentdeepm

ixingmethod(DMM)can

reduce

settlementandincreasestabilityofsoft

ground

Deepm

ixingmetho

diswidelyu

sedinsoft

ground

improvementinChina,e

speciallyin

highwa

y/railway/engineering.


6/33


7/33

Slurrysinglemixingmethod

resultin

gininsufficientsoil-cem

entmixing,

groutin

gspill,colum

nstrengthd

ecreasingwith

depth

Disadva

ntagesofconventionalDMMinC

hina(1)

Slurrysinglemixingmethod


8/33

spill


9/33

insuffic

ientmixing


10/33

Smallcolumnspacin

g,andcushionorgeosynthetics

reinforcedlayerare

oftenrequire

d,whichcau

se

highco

st.

Disadva

ntagesofordinaryDM

MinChina(2)

0.

8

1.

0

1.

2

1.

4

1.

6

1.8

010

20

30

40

Frequency(%)

C

olumnspacing(m)

875samples

Cushio

norgeosynthetic

s


11/33

T-shape

ddeepmixingmethod

Ane

w

typeofdeepmixedcolumn

calle

dT-shapeddeepmix

ed(TDM)

colu

mnwasde

veloped(L

iue

t

al.,

2007a;2007b)

inordertosolvethe

aboveproblem

s


12/33

ATDM

columnh

asalarge

r

diam

eterinthe

shallowdepth,and

asmallerdiame

terinthe

deep

depth,creating

adeep-mi

xed

colum

nanalogo

ustotheletterT.


13/33

Them

ixingblade

sspreado

utward

where

enlargedcolumncap

swere

constr

ucted,whilemixingblades

shrunkinwardatthedesig

nedlevels

where

deep-depthcolumns

were

constr

ucted


14/33

F

ieldtest

SketchoflocationofHusuzhe

Highway


15/33

Thehighwayhas6lanes,andtheembankment

heightwas~4m;

TDMs

itewas50m

wideand100

mlong;

Aconv

entionalDM

treatedsitewasplacedcloseto

itforcomparison.

In-situ

CPTUtestsandlaboratorytestswere

conduc

tedforsitecharacterization.


16/33

TDM

DM


17/33

CPTUtests

20

18

16

14

12

1086420

0

1

2

3

45

20

18

16

14

12

1086420

0

50100150200 2

018

16

14

12

1086420

05

0010001500

qt(MPa)

Depth(m)

fs(kPa)

u

2(kPa)

20

18

16

14

12

1086420

0

1

2

3

45

20

18

16

14

12

1086420

0

50100150200 2

018

16

14

12

1086420

05

0010001500

qt(MPa)

Depth(m)

fs(kPa)

u

2(kPa)

TDMsite

Conventional

DM

site


18/33

Typicale

ngineeringp

ropertiesofs

oilintestsites


19/33

Geometrydesignparame

tersofTDMco

lumns(unit:m)

Equivalentareare

placementratio

was0.108


20/33

Geometrydesignparameters

ofconventionalDMcolumns(unit:m)

Areareplacementratiowas0.116


21/33

I

nstallationofTDMcolum

n

Column

installation


22/33

InstallationofconventionalDMcolumn

Column

installation


23/33

PortlandcementType32.5inChin

awasused.

water-c

ementratio(w

/c)was0.55,

injectionpressure

was0.3

MPa.

Cementcontent(cem

ent/wetsoil)was15%.

Rotatio

nspeedwasa

bout60r/min

.

Penetra

tionandretrie

valratewas~

0.8m/minfo

r0.5

mdiam

etercolumn,~0.6m/minfor

1mdiametercolumn.

Mixing

twicefor0.5m

diametercolumn,mixing

fourth

for1m

diametercolum

n.

Totalconstructiontim

eforTDMsitewas80%o

fthe

conventionalDMsite.

Column

installation


24/33

TDMs

iteafter

columninstallation


25/33

Sixcolu

mnsrandomly

selectedforco

ring28daysafter

installat

ion,unconfinedcompressive

testingwas

conduct

edforcoredsa

mpleswith50

mmdiameterand

100mm

length.

monitor

ing

TestP

rogram


26/33

SomeR

esults-co

lumnquality

18

16

14

12

1086420

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Unconfiedcompressivestength(MPa)

Depth(m)

TDM

ConventionalDM

Qualitiesofthecolum

nsinstalledin

thetwosites

were

quitesim

ilar.

Lowove

rallCOVism

ainlyattributedtothedoub

le

mixingm

ethodadopte

dforcolumn

installation.


27/33

Ground

settlement

Thefin

alreadingat290days

indicatesth

at

theto

talsettleme

ntoftheTD

Mcolumn

treate

dgroundw

asonly67%

ofthatofthe

conve

ntionalDM

columntrea

tedground.

30

0

25

0

20

0

15

0

10

0

5

000

30

60

90

120

150

180

2

10

240

270

300

012345

Settlementmm

TDM

convention

DM

Embankmentheightm

Tim

e(days)


28/33

Lateralmovemen

t

Lateralmovementsof

soilbelowtoesofembankments

20

15

1050

0

10

20

30

40

20

15

1050

0

10

20

30

40

Late

ralmovement

mm

Depth(m)

TDM

9d

34d

49d

82d

98d

137d

164d

197d

225d

Lateralmovement

mm

Depth(m)

ConventionalDM

9d

34d

49d

82d

98d

137d

164d

197d

225d


29/33

TDMw

asdevelopedin2004,hasbeenappliedinm

ore

than30

projects,withover1500000m3ofsoftsoils

treatedinhighwayapp

lications,from

2005-2011.

TDMapplication

s


30/33

Diameterofdeep-depthcolumn(d)is0.5-0.7m,the

typicaldiameterofcon

ventionalDMcolumninChi

na.

Diameterofcolumnca

ps(D)is0.9-1

.2m,approxim

ately

2timesthatofdeep-depthcolumn.

Column

length(L)is1

1-25m,colum

ncaplength(L1)is

2-4mformostcases.

Column

spacing(S)is

1.7-3.2m,muchlargerthanthatof

theconventionalDMc

olumns(typically1.0-1.6m)

TDMapplication

s


31/33

TDMcansavecementandconstru

ctiontime

comparedwiththeco

nventionalDM

.

Totalsettlementandt

hemaximum

lateralmovem

ent

oftheTDMs

itewere

only67%and31%thatof

the

convent

ionalDMsite

.

TDMm

ethodisamo

reeconomica

ndeffectivethan

theconventionalDMmethodforso

ftground

improve

mentC

onclusions


32/33

Ac

knowled

gements

Hardw

orksofmyre

searchgroupandgradua

te

students.

Sponso

rshipsfromNationalScie

nceFoundat

ion

ofChina(No.

50879011)

andJiangsu

Province.


33/33

Thank

you!

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Coloane AA - profil T - Liu PPT.pdf