DIEN BAN KHOA HOC CONG NGHl
NGHIEN CU'U PHUdNG PHAP TINH T O A N BIEN DANG CUA
K H 6 | DAT Y i u DI/OC GIA c6 TRU D A T XI M A N G
STUDY ON THE MODIFIED IMETHOD TO CALCULATE DEFORhAATION OF THE SOFT SOIL IMPROVED BY SOIL CEMENT COLUMNS T S . L E B A V I N H
Khoa ky thuit Xiy ddng - Trddng Dai hoc Bich khoa TR HCM, Email: [email protected] OT 0913713704
F Tdm tit: Hign nay, khi tinh todn 66 lun S, ciia khdi 6k ySu di/dc gia c6 b^ng trg Ck xi mang, nhi^u phi/dng phdp d^u tfnh 'theo ly thuygt dan hoi thdng qua dinh lu§t Hooke. Khi dd dd lun S, dUdc tinh ddn giSn, chim xet sh dnh hi/dng ciia ma s^
xung quanh khdi gia c6, chi/a x6t dSn sU gidm i^g sudt tiieo do sau, va md dun bi^n dang cua khdi gia c6 chi difdc tinh trung binh, chifa xet din ti/flng tac gitte tru vd dat. Bai bdo ndy d6 xudt mdt cdch tinh phu hOp, khi c6 x6t din cdc ylu t6 ti^n, ai xdc djnh 66 lun S, cua Will dat y^u di/dc gia c6 blng try 6k xl mSng.
Tif khda:Bidn dang, tru dit xi mSng, ma sat xung quanh, md dun bidn dang.
Abstract: Defonnation S, of the soft soil block improved by soil-cement columns is usually calculated by the basic theo- ry of elasticity through Hooke' law. This calculation is very simple, because It ignores the sumjunding friction of the rein- forcement block, the sti-ess reduction w'rth deptii, and modulus of deformation of improved block is calculated witiiout the inter- action between columns and soft soil. This paper proposes a metiiod which takes into account the above factors, to detennine tile settlement of the soft soil block improved by soil-cement columns.
Keywords: Defonnation, soil-cement columns, surrounding friction, modulus of defonnation.
1.Gldl THIEU
Ngdy nay cdng nghe ddt trdn xi mdng da rdt pho b i l n vd dem lai hieu qua cao trong viec x d li ndn ddt y l u . Tuy nhien cde co s d ly t h u y l t d l tfnh todn b i l n darig cua ndn ddt y l u gia co try ddt xi mdng vdn chua n h i l u , ddc biet Id d V i e t Nam. Do dd viec nghidn edu v l eo s d ly t h u y l t d l tinh todn b i l n dang Id r i t c l n t h i l t . Hien nay, khi ti'nh dd lun S^ cua bdn than khdi ddt y l u dugc gia cd try ddt xi mdng, hdu h i t ede phucmg phdp d l u tinh theo ly t h u y l t ddn hdi thdng qua djnh ludt Hooke, e=a/E . Khi dd do lun S-\ dugc tfnh don gidn, chua xet d i n dnh hudng ciJa ma sdt xung quanh khdi gia cd, chua xet d i n s u gidm Ung s u i t theo dp sdu vd md dun b i l n dang ciia khdi gia cd chi dugc tinh trung binh, ehua xet d i n tuong tac giQa try vd ddt. Vdi cdch tinh nhu thd se chua sat vdi thuc t l , vi trong thyc t l phan Ong thuy hda xi mdng se lam mdt nudc trong n i n , ddng nghTa vdi vide ma sdt giOa try va ddt tdng dang ke. Ngodi ra, anh hudng ciia tdi trpng ngodi se gidm ddn theo dd sau. Vi vdy de cd dugc dd Wn chinh xdc khi tfnh liin cho n i n ddt y l u gia cd try d i t xi mdng ta c l n cd phyong phap phu hgp de tfnh b i l n dang ciJa ban thdn k h i i gia ed. Trong bdi bdo ndy tdc gia d l xudt mdt edeh tfnh b i l n dang ciia bdn ttidn khdi gia cd, sau dd s d dung sd lieu quan t r i e thyc t l vd phuong phap phdn t d hdu han de kiem chiing lai edng thiic gidi tfeh da d l xudt.
2. BIEN DANG,CUA K H 6 | D A T Y i u WOC GIA CO BANG TRU B A T XI MANG
Dp lun cua n i n d i t y l u gia cd try ddt xi mdng dugc tinh bdng tong dp lun S, ciia ban thdn khdi gia cd va dp lOn $2 eua n i n ddt bdn dudi khdi gia ed nhu trong hinh 1.
T& trong [Mn b6 06u. q
H i l l l
if
1
Hinh 1, Ccic dp tun thanh phin cua nin gia cd
Theo cdc phuong phdp tfnh hien nay, dd lun S^
eiia ban thdn khdi gia cd ducft: tfnh ddn gidn nhu sau:
qH qH
S,= E„ aE^+(l-a)E,
(1)Trong dd:
Si - dp hin cua bdn than khdi gia cd;
q - tai trpng phan bd tren khdi gia ed;
H - e h i l u ddy khdi gia cd;
a - ty dien tfch thay thd;
Ej - md dun ddn hdi vdt lieu tru;
Es - md dun b i l n dang ciia ddt xung quanh try.
Theo cdch tinh ndy thi dd Itin S, ciia bdn thdn khfii gia ed dupc tfnh dua tren dinh ludt Hooke: E=a/E, trorw dd bd qua ma sat thanh cua khdi gia cd, vd yng suat do tdi trpng ngodi khdng thay doi theo e h i l u sdu, trong
NGUdi XAY DUNG SO THANG 5 & 6 - 2015
N G H I E N c u r u P H U O N G P H A P T I N H T O A N B I E N D A N G . . . khi theo thyc t l thi ma sat thdnh eiia khdi gia c6 vdn
tdn tai du khd nhd va dng s u i t do tai trpng ngodi se gidm dan theo c h i l u sdu.
Trong bdi bdo ndy, mdt edeh tfnh dugc d l xudt vdi s u hieu ehinh cdng thuic tfnh liin d tren bdng each xet them: ma sdt xung quanh khdi gia ed, s u gidm d i n anh hudng cua tdi trpng ngodi va s d d u n g module b i l n dang trung binh ciia khdi gia ed phili hpp hon.
3. PHUONG PHAP CAI TIEN B I TINH TOAN BIEN DANG CUA K H 6 I B A T YEU OUOC GIA c 6 BANG TRU OAT XI M A N G
Theo Alen [4], phuong trinh phdn bd dng s u i t trong khdi gia ed (do Alen eai t i l n t d edng thiJfC eua
B + 2x
I{B,x,z) = -
'Az^+{B+2xf +arctg(-— ) +
+2z.-
2z B-2x 4z^+{B-2xy +arctg(: B-2x.
(2)
LTng suat theo dp sdu trong khdi gia cd do tdi trpng ngodi q tao ra:
a{q,B,x,z) = qJ(B,x,z) (3)
Ma sdt don vj xung quanh khdi gia cd dupc tfnh nhu sau:
f,={l-sirnp)c7'jgg) + c (4)
Trong dd:
c, (p Idn lugt Id luc dinh vd gdc ma sdt trong cua ddt y l u xung quanh tru.
Md dun b i l n dang ciia khdi gia ed (do H.Ochiai &
M.D.Boton d l xudt ndm 1994) duoc tfnh nhu sau:
(b-l)a + l
- • ( 5 )
F = -
E''
1-
i =
(6)
Trong do: _
Ebh)d( ~ mo dun b i l n d^ng cua khdi gia c6;
a - ty diSn tich thay th§;
Hlnh 2. fl^l- »• mJns '^ """"S Itpimni
Hinh 3. D^(- w mSng li nhdng ldp dUng
b - he so tap trung umg su§t:
m = 1- S| phu thupc he s6 poison cua d i t ; S| duoe xSo dinh dira theo hlnh dang ciJa d i t tron xi mang (hinh 2,3,4,5):
/•• •• • • •
•. •••
'/.
IXi-v.)
^T^^
Vimti^.Dit-ximmgli khdi clu
nhdng Hlnh 5. Dat- xi ming li nhdng khdi tm Xet khdi ddt y l u cd c h i l u rdng B, c h i l u ddi L, c h i l u cao H dugc gia ed bdng cdc khdi ddt xi mdng hlnh try:
' 1
H
q
|IIJ(BA4
Hinh 6. Scr dd ^nh ldn cho khdi gia cd Chia khdi gia cd thdnh n h i l u Idp phdn td cd c h i l u day dz. Xet iuc dimg tdc dung Idn 1 Idp phdn td d d t :
1
i -J
1 I i
t;
Hinh 7. ttfp ptian td dat gia c6 c6 chiu diy dz B i l n dang tuorig d6i ciJa ItSrp ph^n t6 duoc tfnh nhi/
qJiB,x,z).B.L-/,.2(B + L).dz
dS=€.dz
H
S= jdS =
0
q.I(B,x,z).B.L-f,.2(B + L)dz' (7)
(8)
B.L.K,, dz
Xet nhQng diem nam tren tri^c qua t§m dien chju
N G l / d l X A Y D U N G s 6 T H A N G 5 ft 6 • 2 0 1 5
NGHIEN ClJfU PHUONG P H A P T I N H TOAN BIEN DANG...
tai, Ithi d6 X = 0:
' qI(Bfi,z)£L- f,.2{B + L)dz .S-\
- > s = -
H
\q.I(B,z)dz- 2(,B + L)
(10)
(11)
S,= \q.I(B,z)dz S,=?^^\f,dz
est:
2q
^/,=|[/„(4z=.B))r
(12)
(13)
\^-rctg[£^- •H42^+B^)) (14) -> S, = % | z,arc/g(^^j+|ln(4z' +5=) ] (15)
2(B + L) B.L \f.dz
^ S , = — ^ i — -(l-sm^>gp.^z'+cz (16)
TLTCSC phucmg trinh (15) va (16)
( B^2q
z..c,g^-J +
+-ln(4z^ + S^'
2 (B + L)ncz-m.z +m, BLq ^
(17)
B + L Tr ,, . V
m, = — — — ( 1 - sin q>jtgip.y + 1 (is)
BL 2q
-^\nB'
(19)Tdcdc phucmg trinh (17), (18), (19), ta cd thi tfnh dupc dd lun S, ciia bdn thdn khdi gia cd. ^
,4. KIEM CHU'NG PHUONG PHAP DE XUAT BANG CAC Md HINH
4,1. Kiem chtfng bang mo hinh thi nghiem cda M.D.Bolton (dai hgc Cambridge)
Theo dd M.D.Bolton da tao 8 try ddt xi mang dudng kinh 30mm, ddi 200mm trong hop vdeh kinh. Xi mdng Portland dugc trdn vcfi hdm lugng 15kg/m' vio trong set Kaolin. Tdi trong thdng ddng dugc gia tdng t&
0.96 din 25kPa thdng qua tim cutig ddt trdn dlu trg (hinh 8) vd cdc thdng sd ddt nhutrong bdng 1.
Hinh 8. Md hinh ffil nghiim cOa Bolton Bang 1. Thdng s6 v$t li$u cOa Bolton
Loai v^t ligu DatxImSng Sgt Kaolin
E (kPa) 17262 4171
V
0.4 0.49
c (kPa) 29.96
2.66
*n
35 0
a{%) 22
4.2. Kiem chtS'ng bang pht/ang phip phin tH hufu han
Md hinh gdm 30 try ddt xl mdng, trdn dlu vdidirdl
Hinn 9. iwo ninn unn wan irong i^laxis 3DF Bang 2. Thdng sd vit lidu trong Plaxis
m iitueit nap
Dat yeu
Tra USt- xi m9ng
Ma hinh
Mohr- Coulomb
Mohr- Coulomb
Mohr- Coulomb
CiGth6ngs6 E«4(Mpa),c=10(l<Pa),q)=25, v = 0 . 3 , H=3m,a=18(liN/m'), k , = k „ = 1 0 ^ ( n i / s e c ) E « 1 . 5 ( M p a ) , c = 1 0 ( l < P a ) , v = 0 , T=16(l<N/m'). 1=0.495, H = 1 5 m , l(.-l(,-10^(rTVsec) E=50(Mpa), c=80(kPa),
<i>=35,Y=17(kN/m'), v = 0 , 4 9 5 , H = 1 0 n l , k , = k , = 1 0 " ( m / s e c )
NGUdi XAY DI/NG SO THANG 5 & 6 • 2015
N G H I E N c u f u P H U O N G P H A P T I N H T O A N B I E N D A N G . . mui cdt id 2 tdm cufng bdng be tdng day 10cm, tai phdn
bd tdc dung len tdm cimg Id q= 7.5KN/m' (hinh 9).
Bang 3. Tdng hep s6 lieu tinh toin S, q (kN/m^
H(m) Ec (kPa) Es (kPa) a(%) B(m) L(in) c(kN/m')
7.5 10 5e4 1.5e3 6.6 10 12 10
8.8 10.87 16.97
5. KET QUA TINH TOAN
B i l u dd so sdnh k i t qud thu duge t d edeh tinh theo ede phuong phdp khde, theo each tinh d l x u i t vdi k i t qud t d md hinh thi nghiem eiJa Bolton dugc the hien trong hinh 10. Bieu dd so sanh k i t qua thu duge t d cdch tinh theo cde phuong phdp khde, theo edng thdc d l xudt vdi k i t qua t d Plaxis cho cac trudng hgp n i n ddt gia cd cd 30 tru, 40 try, 50 try, 60 try dugc the hidn trong ede hinh 1 1 , 12, 1 3 , 1 4 .
Cic pbmrng pUp kUc Thf ngU^ni Phmmg pUp 0^ xalt Hinh 10. So sinh kit Qui tinh lun theo cic phddng pbip vdi kdt
Cic [diinnig phap kbac P U i b 3DF Pbmmg fdiip dl xiul Hinh 11. So sinh kdt qui tinh lun theo cic phddng phip vdi kdt
qui td Plaids cho trddng hdp 30 tru
* Nhan xdt:
Qua cdc b i l u dd trong hinh 10, 1 1 , 12, 13, 14 ta thdy k i t qua tinh todn dd liin S, thu dugc t d edng thUc
Si(mm)
10.04
1
8.97I
CJJcphdinigpUpklific Plaxis 3DF Pbinmg phip (1$ xolt Kinh 12. So sinh kdt qua b'nb Idn theo cic phddng phap vdi kdt
qui td Plaxis cho tnSdng hdp 40 tru Sl (nun)
M
Cic pbmmg pbip khic Plaxb 3DF Phmmg pbip (^ xait Hinli 13. So sinh kdt qui tinh Idn theo cic phddng phip vdi ket
qui td Plaxis cho tn/dng hdp 50 tm Sl(iiim) :' 7.7
Cic phinnig pbip khic Plaxis 3DF Phinmg phip dl suit Hinh 14 So sinh kit qui tinh Idn theo cic phddng phap vdi kit
qui td Plaxis cho trddng hdp 60 tm d l xudt nhd hon k i t qud thu dugc t d cac phucmg phdp khde va gdn sat vdi k i t qua thu dugc t d md hinh thi nghiem, hay xdp x! vdi k i t qud thu dugc t d Plaxis. Cy the trong hinh 10 k i t qud thu dupc tir cdng thdc d l xudt Idn hem k i t qud thu dugc t d md hinh thf nghiem cua Bolton 29%, vd nhd hem k i t qud thu dugc t d cac phucmg phdp khac 38%.Trong cde tlinh 1 1 , 1 2 , 1 3 , 1 4 k i t qua thu dugc tdedng thifc d l x u i t nhd hem k i t qua thu dugc t d ede phugng phdp khde khoang (27 -§- 31)% vd nho hem k i t qua thu duge t d Plaxis khodng (7 H-10)%- Qua dd eho thdy each tinh d l xudt cho k i t qud xdp xi vdi k i t qud t d Plaxis, the hien duoe nhdng
N G U d i XAY D U N G s 6 T H A N G 5 & 6 • 2 0 1 5
NGHIEN Cli^U PHUONG PHAP TINH TOAN BIEN DANG...
dng XLT thuc te cilia khoi dat yeu gia co tru dat xi mang.
6. PHAN TICH CACH X A C OINH MO B U N D A N H 6 I C U A V A T LIEU TRU B A T XI MANG.
Theo tieu chuan Viet Nam TCVN 9403:2012 [1 ], khi tinh toan dp liin S, cua khdi gia c6, thi thdng s6 E,, la md dun dan hoi cua vat lieu tru. Theo nhu mot sd de xudt gia trj mo dun dan hdi nay cd thd dugc lay t d t h i nghiem nen mot true co nd hdng vi day la thi nghiem dem gian va rat pho bien, Tuy nhien vdi each xac dinh nhu vay thi chua phii hop vi thuc te ngoai hien tru'dng xung quanh cac tru dat xi mang con c6 ap luc ngang cua dat nen, cdn trong thi nghiem nen mot true co nd hdng thi khdng cd ap luc xung quanh mau thi nghiem.
Do vay, day la mot trong nhurig nguyen nhan gay ra s y chenh lech giu'a gia tn md dun dan hoi ciia vat lieu try ddt XI mang thuc td lai hien trucmg va gia tri md dun dan hdi cua vat lieu tru dat xi mang thu dugc tis thi nghiem nen mpt true cd n d hdng, Nhieu ket qua thi nghiem hien trudng da cho thay su chenh lech nay.
• Theo thi nghiem hien trucmg ciia Baker [7] tai cong trudng Loftaan mien nam Goteborg, Thuy £)ien
da phan tich b i l n dang theo dp sau cua tru d d t « mang. Theo do 30 try ddt-vdi-xi mang ducmg kfnii 0.6m dugc dat d d p sau 6m nhdm p h u c v u choeacttif
MaE«l Losdccll —,
ZI!liB
\\
^
icin
H C ' -
r\
Hinh 15. Thi nghiem hien tl
' I ' 1 ~ ' i ' i I I i i .< 't > } * « II
VtriKil MhiBiiIti { E » |
' 1 I I ' I ' i • 4 •! 1 3 »
VuilClKcfMMMWI ! • ColuiimS
10
/ " " ^ / /
L^ ^
CMe-3 i CUe-2
j
" i
Vq.-"
VciMil dtbrmtilsti In n]
Hinh 16. Kdt qui thu dddc tdthi nghiem hien trddng.
I N G U d i XAY D U N G SO T H A N G 5 & 6 • 2 0 1 5
O 0.005 0.01 0.015 0.02 0.O25 0.03 NonoalizaJ vertical tenleoiem, d/B Hinh 18, Ket qua thu dddc td thi nghiem trong phong cua M D Bolto
£ • 7 0
> ; 5 o
I"
I 30
S 20
.|,„
> 0
0 0.005 0 . 0 1 0.015 0.02 0.028 0.09 Nonnabzsd vcrtial settlemeDt. d/B Hinh 19. Kit qua thu dddc (d mo phong s6 cua M D. Bolton
. . . . J . . . . / j
I/I /1
ll/^\ '
r 1
" " ! " "
Out-
....
I l l )
2
....
%/qr*o
1
NGHIEN cufu PHUONG PHAP TINH TOAN BIEN DANG..
Hinh 20. Md hinh thi nghiim hien tnidng cua c6 GS.TS. Nguyin Tn/dng Tiin
nghiem khac nhau.
Thf nghidm eho k i t qud md dun ddn hdi cua vdt ii^u try thyc t l d h i | n trudng Id E^ = 220 MPa, trong khi k i t qud thi nghiem nen don ed E^ = 60MPa.
• Theo md hinh thi nghiem trong phdng cua M.D.Bolton cd md dun ddn hdi cua vat lieu tru thyc t l d hidn trudng Id E<. = 65,3 MPa, trong khi k i t qua thi nghiem ndn don eho k i t qud Ej. = 17,26MPa.
• Theo thf nghiem hien t r u ^ g eua GS.TS N g u y i n Tru&ng T i l n [2] tai qudn Lidn Chieu thdnh phd D d Ndng: theo dd try d i t xi mang e h i l u ddi 7,5 m dugc tgo ra vdi hdm lugng xi mang 360kg/m^ dugc t i l n hanh ndn tmh, t h i l t bj do b i l n dang dpc true Id strain gage Geokon 9411.
Thf nghidm cho k i t qud md dun ddn hdi ciia vdt li^u try thyc t l 6 hidn trudng Id E, = 2130 MPa, trong khi k i t qua thf nghidm ndn don cd E^ = lOOOMpa.
T d nhdng sd lieu thi nghiem hipn trudng neu tren cho thdy ed s g chenh Idch dang k l , t d (2,U3,7) ldn, giQa md dun ddn h i i ciia vat lieu try thuc t l d hidn trudng vd md dun ddn hdi eua vdt lidu try thu duge t d k i t qud thi nghidm ndn dem.
7. Ktr LUAN VA Kl^N NGHj
Trong vide tfnh todn dng s u i t , b i l n dang cua n i n d i t y l u dugc gia cd bdng edc try ddt xi mdng theo mdt s l phuong phdp hidn nay, cu the Id tfnh todn dp lun dp lun Si eua bdn thdn khdi gia ed duge tfnh dua tren tSnh ludt Hooke £=a/E bd qua ma sdt thdnh cCia khdi gia cd, va anh huong eua tdi trgng ngodi xem nhu khdng gidm theo e h i l u sdu, trong khi theo thyc t l thi ma sdt thdnh cua khdi gia cd vdn t i n tai dii khd nhd vd dng s u i t do tai trpng ngodi gdy ra sd gidm ddn theo ehilu sdu. Khi tinh todn n h u t h i se eho k i t qud khd an todn, vdi k i t qua dd lun cua khdi gia cd Idn hem t d 2 5 % d i n 3 5 % k i t qua thyc t l tiJy theo dd ldn eiJa ty dien tfch thay t h i . Do do, khi s l lugng try cdng n h i l u thi ma sdt xung quanh khdi gia ed edng ldn vd phdn dng thuy hda xi mdng cdng n h i l u Idm cho n i n tang khd ndng chju luc ndn dd ehenh lech gida cae phuong phap cdng ldn. Cho nen, tfnh todn theo cdch ndy se it hieu qud kinh t l , nhdt la ddi vdi cae cdng trinh dudng khi
khdi lupng thi edng Idn.
- Vdi each tfnh d l xudt trong bdi bdo ndy, da ed xdt d i n ma sdt eua ddt xung quanh khdi gia cd va s u g i a m eua dng s u i t do tai ngodi gdy ra trong vyng ddt duge gia cd. Cac k i t qud phdn tfch thu dugc budc ddu cho thdy s u phu hgp vdi b i l n dang thyc t l cua n i n ddt dugc gia cd bdng cdc try xi mdng ddt.
- Khi tfnh todn dp lun S-| cua khdi gia ed, n l u Idy gid trj md dun dan hdi eiia vdt lidu try t d thf nghiem ndn mdt true ed nd hdng thi chua phu hgp vi thuc t l ngodi hipn tnidng xung quanh ede tru ddt xi mdng edn cd dp luc ngang eua ddt n i n , cdn trong thf nghiem ndn mdt true cd nd hdng thi khdng c6 dp Iyc xung quanh mdu thf nghidm. Do vdy, ddy Id mgt trong nhdng nguydn nhdn gdy ra s u chenh lech gida gia trj md dun dan hdi cua vat lieu tru ddt xi mdng thue t l tai hien trudng vd gid trj md dun dan hdi cua vat lieu try d i t x i mang thu dugc t d t h i nghiem nen mdt trye c d n d hdng. T d nhung sd lieu thf nghidm hien trudng ndu tren eho t h i y cd s u ehdnh Igch ddng ke, t d (2,1 #3,7) ldn, giUa md dun dan hdi cua vdt Hdu tru thyc t l d hien tnjdng vd md dun ddn hdi cua vdt lieu try thu dugc t d k i t qua thf nghiem ndn don. •
TAI LIEU THAM KHAO
1. Tieu chuan Viet Nam TCVN 9403-2012, Gia cd dat ndn yiu - Phddng phap tru dit xi ming
2 D 6 Hiiu Dao, Phan Cao Thp, Nguyen Trifflng Ti^n. "Xie dinh h$
sd sdc chiu til cOa coc dit xi ming thong qua md hinh thi nghiim Full scale vdi thiit bi do bidn dang doc true", T?p chi Dia Ky ttiuat s6 3-2014. nam 2014.
3. Alamgir.°S(fess-S(ra/n distnbution in embankment reinforced by columnar inclusion" (1996).
4. Alen, C. "UmelCement Column Stabilized Soil - A New Model for Settlement Calculation" {1Q\Q).
5. Halcan Bredenberg, Goran Holm, Bengt B.Broms "Dry Mix Methods for Deep Soil Stabilization".
6. John RCarter. "Deformation Analysis In Soft Ground Improvement" (2011)
7. Sadek Baker "Deformation Behaviour of Lime/Cement Column Stabilized Clay" {2000).
N G U b l X A Y D U N G SO T H A N G 5 & 6 - 2 0 1 5
