TAP CHi KHOA H p C CONG NGHE GIAO THONG VAN T A I . SO 22-02/2017 61
NGHIEN Ciru ITNG DUNG COC DA TRONG XU" LY NEN DAT YEU
RESLARCH AND APPLICATION ON SOFT SOIL FOUNDATION TREATMENT BY BALLAST COLUMN TECHNOLOGY
Nguyin Thanh B^t', Do Thanh Timg' . , ''Khoa Ki'Thudt Xdy Dimg nhdnr,'.r!fA?i!"-"^'f'"'' ^^ P'.'^^^S phdp xiT ly gia c6 nhi ddlyiu bdng coc dd. hm qua ciia bien phap cac da khi img dung vao cdng trinh Nhd mdy Nhiei dien Nghi San. Thanh Hod
Tir khda: Coc dd. cdng trinh Nhd mdy Nhiei dien Nghi San
Abstract: This paper presents a study on application of ballast column technolom' on »eak sod treatment, the effection of this technology in Ngh, Son Power plant project. Thanh Hoa
Keywords: Ballast column, gravel - ballast column, Nghi Son Power Plant Chi so phdn logi: 2.4
l.Giol thieu
Xii ly nen 3at yen trong xay dimg la mot cong tac kho khan doi hiii nhieu hieu bifit chuyen mon, may moc cong nghe va l6n kem Hien co rat nhieu bien phap xii ly nSn dSt yeu dang dirge sir dung lai Viet Nam, m6i bien phap deu co uu nhuoc diem rieng, ciang nhu pham vi rnig dung khac nhau.
Coc da la mot bien phap da dugc nghien cizu ling dung tit nhiing nam 50 the ky truoc Qua hon 60 nam [ihal trien, phuong phap nay da Ircf nen pho bien tren the gioi (dac biel la lai My, Diic, An Do) cung nhu he thdng !y thuyet tinh loan thiet k4 da dugc hoan thien.
Tuy nhien tai Viet Nam, cgc da chi dugc sii dung rat han che tai mot so cong trinh nhu:
Bai xuong chS tao Cang ha luu PTSC - thanh pho Vung Tau; nen nha kho Nha may Bgt mi Phu My - thanh ph6 Viing Tau, Nha may Vifon - Long An, Nha may Dien Hai Phong.. D6ng ihol cung co rat il cac cong trinh nghien ciiu v^ cong ngh§ nay tai Viet Nam. Vi vay trong noi dung bai bao, tac gia mu6n gop phan lam sang to hieu qua cong nghe nay ciang nhu nghien ciiu cac phuong phap tinh toan nen gia c6 bang coc da.
2. Phuong phap coc 6A:
Coc da diroc t?o ra bang each dong, an ong thep rong bit dau vao dat den dg sau thiel kL Sau do d6 da dam (cap phoi lu 8mm - 50mm) vao trong 6ng thep, mo mui bit dau 6ng thep, vira do vira rung de da dugc len chat, ciang co ih^ sir dung dam nang de lang hieu' qua, Khi coc dugc dfl day da thi ong
ihcp duge nil len hoan toan Da da duoc dam chat nam lai Irong dai, va hinh thanh nen coc da (hinh 1).
Duong kinh coc da thuong. 0,5 ^ 1,2m, khoang each giOa cac coe; 1,5 - 2,5m; chiSu sau xii ly thirong la: 6 - 20m.
U'u diem ciia phuong phap coc da: [6]
- Coc da CO siic chju tai Ion {co the ien den 40 - 50 tan), co the sau den 30m;
Vat li?u da dam co kha nang thoat nuoc rat lot nen coc da dong vai Iro la dudng thoat nuoc dung trong dk, giiip day nhanh qua trinh co kel;
- Coc da khicn dat nen xung quanh bj ep chat Idiien cac chi lieu ciia dal cai thien rat dang ke. Tang siic chflng cat, he s6 nen liin giam, giam nguy co hoa long ciia nen,
- LTng dung eho hau het cac loai dat yeu: cat roi, cat hot de hi hoa long; biin set, dal set mem yeu ven song, bien;
- Rial ngan thoi gian xii ly nen yeu.
Nhuoc diem ciia phuong phap coc da:
v>i . . .
Thi cong gay chan dong va lieng on, - Chi phi se lang khi khong co san ngudn vat lieu lai dia phuang,
Dal phai co luc ep hong du Ion de iranh no hong coc da
al of Transportation Science and Technology, Vol 22, Feb 2017
Dja tang khu vu-c xay dung nbir sau
L ^ AB E>dl san lip lin biin,
^^~. soi.chalhihjcomauvangnau.
( AB 1 4,0 (Jo n^u. Irgng thSi deo mem
Ll>p C2 sa lan phu sa mau r 1 ^ • lliiideo
/ ha dng thep. 2. nap lieu ket hop dam lap lai cho timg dot: 4. hoan Idl 3. Die diem cong trinh nghien cihi:
[1|;|2I
Nha may Nhiel dien Nghi Son nam Irong khu Kinh ik Nghi Scm thuoc linh Thanh Hoa va muc dich xay dung Nha may nham cung cap dien cho khu kinh le nay.
Bang 1. Cdc chi lieu dia ky ihudl
L o p D 2 SelpbacaLirauvan^
Hinh 2. Hinh Iru hd khoan va CQC dd
k^ hieu Dung Irpng l^r nhien, y He . 6 rong, D p a m . w Lire dinli; c
Modim BD. E„
He so tliain. K, Dtm
lim'
kPa a?
kPa m/s
L A p d a t AB
1,83 0,893 30,5S 9,4 20,71 3900 6.1 1 0 '
C2 1,81 0,763 26,64 12,2 19,1 6-200 7.1 1 0 '
Dl 1.92 0,825 29,89 14,3 23.1 8 600 6,3 10"'
D2 2,05 0,588 20,49 36,4 23,6 15 400 2.S 1 0 ' Muc nuoc ngam nam tai cao do {-0,4 - -
0,5 m).
• Nhiem vu thiet lie xir ly nen Kha nang chiu tat ciia nen dal 200kPa Do liin ciia nen khong qua 100mm,
• Thong so thiet ke coc da - Duong kinh cpc. dSOO.
- Chicu dai coc Lo= 10,0m, - M9I bang bo tri coc O vuong 1,7ITI X 1,7m.
- Ty dien fich fhay the- ac = Ac/A< = 0.211,
Goc ma sal (rong ciia vat lieu da, 42"
Hinh 3. So dd hi) n,, oc da iheo liroi 0 1 udng 4. KSt qua do liin nen theo phirong phap giai tich va Iheo thi nghiem ban nen hien trirdng
• D6 lun cua nen khi chira xir Ey coc da |4|
Tinh toan theo TCVN 9362 - 2012, Tieu chuan thiet ke n^n nha va cong trinh.
- Do liin on dinh. S = 231 mm
TAP CHi KHOA HOC C O N G NGHE GIAO T H O N G VAN XAl, SO 22-02/2017 Thoi gian dat do co kSl U, = 90%- 46
nam,
• Do iiln ciia nen sau khi da xir ly bSne
coc d i | 5 | ® Truong hop da gia cS coe da duoc tinh
toan theo TCCS 2015 IBST: Tru da dSm ning sau - Tieu chuan ihi cong va nghiem ihu
Do liin on dinh ciia ngn: S = 46mm Do liin ciia nen iheo thoi gian duoc ihl hien nhu hinh sau:
Hinh 4. Bieu do dd liin Iheo thai gian cua nin trudc va sail kill gia cd bdng coc da
• Kiem tra n i a su' diing cgc d^ b i n g thi nghiem ban nen hien trutnig: |2]
Dirge thirc hien tai hien trudng theo TCVN 9 3 5 4 - 2 0 1 2 , kll qua nhu sau:
BlEu Ob aUAN HE GICTfl M l THflNli VA. D f LUN ,
Hinh S. Bieu do quan he dd lim i'« lai Irong iheo thi nghiem bdn nen hiin truang
• Nhan x^t
- Theo kk qua linh loan, khi chua xir ly nSn CO d? liin vuot miie cho phep sau 6 thang va sau 10 thang, do lun vuol miic 43%, khong dam bao cho cong trinh va vi?c van hanh may.
- Trudng hop sir dung coc da, do liin cu6i Cling ciia nen chi la 46mm; vugl miic yeu cau va sau 10 thang da dat do co ket >
90%, do liin du con Iai ia 4 mm khong dang kl
- Ket qua thi nghiem cho thay ngn dal do liin 32,5mm voi miic tai trong yeu c3u, liic la dat yeu cau ky thuat
- Kel qua thi nghiem chenh lech khoang 22,5% so voi tinh loan, tuy nhiSn kk qua linh loan CO xu hucmg nghieng vl an toan nen vln dam bao yeu cau ky Ihual
5. Ung dung ph5n mSm Plaxis tinh toan nen gia co coc da:
Phan mem Plaxis dugc phat trien boi eong ly Plaxis B.V (Ha Lan), la phin mim hieu qua trong phan lich dia ky thuat iing dung phucmg phap phkn tu hiina han.
• Bai toan mo hinh mot coc da doc lap
Kel qua linh toan va so sanh voi thi nghiem ban nen hien tmong ihl hien nhu bang 2.
Bang 2. So sdnh do lim giira nen hiin Irirdng va
Tai Irong (kPa)
0 50 100 150 200 250 300 350 400 450
Nen tmh (cin) 0 7,5 15.8 23,7 32,5 41,9 55,7
Plaxis 3D (cm) 0 3.5 7,6 13.2 22,1 33.6 49,3 70,2 101,2 154,4 Sir dung phien ban Plaxis 3D Foundation 1 6 de mo hinh hoa mgt coc da doc lap chiu tai trong phan bo muc dii.h cua cong lac nay la nham kiem tra ket qua mo hinh ihong qua so lieu nen hien truong Dieu kien bien (x y z 20m 20m 20 '^m) Cac thong so mo hinh duoc trinh biv nhu ban^ 3
Hinh 6 U( hmh
I, Journal ofTransportation Science and Technology, Vol 22, Feb 2017
Bang 3. Cdc llidng td md hinh
r.^,i
M o hinh U-ngxu Dung Irpng t u
Diiii)! trgng ban
H ¥ S 0 U , a m k „ k ,
l l ^ s o l h a m k . HC-s6PDis5on,v Modun bien dang,
E „ [ L i i c d i n h c „ / Goc ma sal trong.
v!
kN/m>
k N / m ' m/day nVday
k N / m ' k \ .n=
<Iy Ban be lun R
]VI400 t = IflCIll
Linear F.laslic N o n porous
2.S
0,2 32.5,10"
C f l c d i
M o r h - Coulomb
Drained 21
21 10 10 0,25 12 10'
1
••2
L o p d u l A B
M o r h - Coulomb Undrained . . J
18,7 0.53 0,53 0,499 3 900 9.4 20,71
C2
C^ulom'b Undraincd IK.I
18,6 0.0061 0,0061 0.499 6 200 1 2 2 1 " . ,
D I
Coulomb Undmined 19.2
19,3 0,0054 0.0054 0,499 S,6fl0 14.3 23,1
m
Coulnmb Undrained 20,5
20,7 0.024 0,024 0,499 15 400 36 4 23.6 6V» ihii Mo hinh Maili - Coulomb diroc clu,in vi cac llidng S'
Hinh 7. Bieu dd so sdnh dd bin giua nen Imh vd kit qud linh toan Plaxis 3D.
• Nhatt xet
Dua vao bieu do la thay duong nen liin o cap lai trpng nho 200KPa gan nhu tuyen tinh.
Khi cap tai nho hon 300kPa, hai do th] gSn vl nhau chenh l^ch 11 %, Mirc chenh lech nay la khong nhieu, co nhilu nguyen nhan' S6 lieu khao sat, thi nghiem khong the phan anh chinh xac cac dac Irung dal nen, he thong ly thuyet linh loan phan lich vln con phai dua tren nhieu gia thiet ly tuong hoa (Vi du Cac lop dal hoan loan dong nhit..)..
Khi lang lai lir 350 KPa tro len din khi nen bi pha hoai. do Ihi biln dang cong nhilu.
Liic nay cac lien kll trong coc da bk dau bi pha v5, cae hat da khong con hen kel lao hinh tru nhu ban dau, do vay tai trong xem nhu tac dung true tilp len dal nin do do gay ra biln dang liin
Mac khac khi nen linh, ban nen co dicn lich Im- xem nhu chi tac dung len dSu coc da, do vay bieu dfl nen liin gSn nhu luyin
J dd}' du de sir dung cdc mo hinh khdc linh Khi tinh bang Plaxis cho mot don nguyen 1,7m x 1,7m luc nay ca coc va dal lam viec dong thoi, do vay bieu do co duong cong cho den khi nen va coc bi pha hoai.
• Bai todn mo hinh tofin bo dien tich chju tai:
- Su-dung Plaxis 3D
Mo hinh cho loan bo dien lich nen cong trinh chiu lai trong phan bo voi kich thuoc 20m X 6,5m, ben duoi la lop be long dem day 10cm tren dicn tich 60m x 30m
mm
^tf^f
Hintx S. Md hmh be coc bdi loan khdng gian 3D - Sir di^ng Plaxis 2D
Thirc hien tuong tu nhirng su dung phan mem Plaxis 2D 8 2, lai trong tac dung len nin thong qua lop be long dem day 100mm.
i M i S
Hinh 9. Md hinh he cpc hdi Ket qua tinh toan
_JAPCHiKHOA HPC CONG NGHE GIAO T H O N G V A N T A I S A oo.r.-,,....
t h e hic. qua linh toan iheo hat mo hinh dugc 'i[iubang4.
c dd qua phdn lich Plaxis 2D vd 3D
Tai trpng (kPa)
150 250 300 350 400 500 600 700
Do lun (mm) 2D 0,0 11,6 24.5 42,6 66,5 58,8 147,4 170,5
3D 0,0 13.6 32,1 63,1 124.7 252,5 485,6 913,4 1720,0 4730,0 8960,0
0 . , . „ 1 ,
Nen 2D pha
Nen 3D pha
Hinh 10. Bieu dd quan he giira tdi trgng vci dd liin theo 02 md hmh 2D vd 3D
• Nh|ln xet
Voi duong kinh D = 0,8m va chilu dai coc da Lo = lOm, tai cap lai trong nho hon 200kPa do liin ciia nen giiia hai phuong phap tinh Plaxis 2D va 3D co su chenh lech khong dang ke,
Khi tai trpng tang len tren 200kPa do liin nen linh theo Plaxis 3D co su chenh leeh rat Ion so vol Plaxis 2D vdi gia Iri hon ba lan lai cip tai P = 300kPa Voi mo hinh 3D trong Plaxis cac phan tu djch chuyen theo ca 3 phuang nen gay ra do liin Ion hon so vdi mo hinh 2D
Khi lang cap lai trong len den P = 700kPa nin 3D bat dau bi pha hoai, la co h^
s6 an loan khi linh loan thiel ke nen gia cd nen bang coc da-
FS=^=^^ 3,5 K
Trong phuong phap mo phong bing Plaxis 3D ta thay md hinh nay gin gidng voi md hinh ihuc ll nen eo thi ap dung d l md phdng linh toan
6. Kh lu^n
Phuong phap coc da co hieu qua dang ke trong cong lae xtr ly nin dit ylu Cu ihl trong cdng trmh Nha may Nhiet dien Nghi Son, Thanh Hoa. phuong phap nay da dap ling duge cac yeu cau ky thuat dal ra. Giiip giam 5 lan dg liin ciia nin va nin nhanh chong dal do cd kll cin thill
- Phuang phap linh loan nin gia ed coc da theo TCCS 2015 IBST- Tru da dim rung sau - Tieu chuan Ihi eong va nghiem thu cho kel qua gan hiong Ur thi nghiem ban nen iTnh valhicn ve an loan.
• Phucmg phap linli loan ling dung phin mem Plaxis 3 0 co the sii dung dl mo phong nin dit gia co coc da va coc da dgc lap Ket qua md phdng tuong lu nhu ihi nghiem ban nen hien truone Phuong phap nay cung cap them cho ky su mot cong cu hnh loan hicu qua, nhanh chdngQ
Tai lieu tham khao
[1] Coiig ty Kiso-Jiban Consultants Co Ltd (2009),
"Ket qua khdo sdi dia chit Cdng Irinh nhd mdy nhiet dien Nghi San "
[2] Cong ty TNHH Nen mong Keller Viet Nam (2010), -Kil qua Ihi nghiim nen tinh ddu c(>c cdng trinh nhd mdy nhiel diin Nghi Sim "
[3]. Lien hiep dia chat cong trinh xay dung va moi Inroiig (2010), "Bdo cao kit qua nen iTnh nin gia cd bdng coc dd"
[4]. TCVN 9362-2012, "Tieu chudn ihiit ke nin nhd va cdng Irinh"
[5]- TCCS 2015 ,"Tni dd dam ning sdu - Tieu chudn thi cdng va nghiem Ihu"
[6] Barksdale and Bachus (1983). "Design and conslruclion of .itone columns vol I" FHWA/
RD-S3/IJ26. 19S3 N g i y o h a n bai: 03/01/2017 Ng^y chuyen phan biSn: 06/01/2017 NgAy fao^n thanh sua bai: 26/01/2017 Ngay chip nMa dang: 02/02/2017
