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_ _ ^ TAP CHi KHOA HQC CONG NGHE GIAO T H O N G VAN T A I , S 6 16-8/2015 |
PHAN TICH HIEU QUA CUA CONG NGHE COC XIMANG-DAT TRONG GIA CO DAT N £ N QUANH u6 DAO SAU STUDY THE EFFECT OF DEEP SOIL MIXED COLUMNS TECHNOLOGY IN REINFORCING GROUND AROUND DEEP
EXCAVATIONS
TS. Nguyin Thdnh Bat, ThS. Bd Thanh TUng Khoa Ky Thugt Xdy Dung
Tdm tdt: Viec xdy dung cdc cdng trinh ngdm hogc cdc tdng hdm, dgc biet Id cdc tdng hdm cd chiiu sdu ldn cua cdc tod nhd cao tdng dd vd dang dgt ra mot thdch thue ldn cho ngdnh xdy dimg vi vdn de dam hdo dn dinh cho hd ddo sdu. Trong nhimg ndm gdn day, cdng nghe coc ximang - ddt dd ddn khdng dinh duac cdc uu thi ciia nd trong viic xii ly vdn di niu trin tgi Viet Nam.
Bdi viit trinh bdy vi vdn di md phdng gia cd hd ddo sdu bdng cdng nghi coc ximdng - ddt (DSMC - Deep Soil Mixed Columns) vdi trudng hap thue te Id cdng trinh hdm vu0 sdng Sdi Gon.
Tit khda: Coc ximdng - ddt.
Abstract: Ensuring the stabilization and safety of executing deep excavations, especially in cases of constructing deep shelters and underground constructions, is always a very hard task. Nowaday, soil-cement columns (or deep soil mixed columns) technology is one of the best choices with lots of advantages to solve this problem in Vietnam.
This article describes the study of the automatic calculating deep soil mixed columns (DSMC) in reinforcing ground around deep excavation in Thu Thiem tunnel construction
Keywords: DSMC.
1. Cdng n g h | cgc ximang - dit: co phu gia. Thudng dung cho dieu ki6n dia Cgc ximang - dit (DSMC) la cgc duge chit mim, thich hgp cho cac nudc d vung lam tii dat tai cho, gia ed vdi mdt hdm lugng Scandinavian.
ximang va phu gia nhdt dinh tuy thudc vdo - Trgn udt: la cat dat va frOn vdi mdt loai va cac tinh chat ca - ly - boa eua dit nin ham lugng h6n hgp ximang bdng luai dao tai khu virc dat cdng trinh. Dudng kinh cgc quay. Hon hgp co the co hoac khdng co phu DSMC thudng la 0,6 - 1,5m va cd the dat gia duge bam bang dp luc nudc. Thich hgp din 40m chieu sau. cho dieu kien dia chat tai Viet Nam.
Mue dich chinh cua cdng ngh6 nay la Trinh ttf thi cong:
nhim tang cudng do cua dit^nln, giam tinh _ Chudn bi mat bdng thi cong thim, tinh liin vd tang siic bin dua fren cac
phan ling CO - ly - hoa cua ba tiianh phdn ^^i^^^khoanT
chinh Id dat tai chd, ximang vd phli gia. , i • J . , , - . , , - Can phai dung loai can khoan chuyen DSMC duge nghien euu va ung duiig ^ ^ ^ g^^ ^^ ^^^ ^ - j j ^ ^ ^ ^ ^ . ^ ^ . ^^^
rgng rai td nam 1976 den nay. Phan Ion van ^j^-.^ ^^ ^^ ^^^ ^^^ ^^ ^.^ ^ . ^ " ^ - ^ - Khoan xoay va xoi nude qua can khoan
d l nghien eiiu duge xuat phdt tir Nhdt Bdn. duge phyt qua voi phun vdi ap suat va van Co hai cdng nghe che tao DSMC hien tdc cao, phd va kit ciu cua dit tao thanh ciu nay: tnic ximang ddt viing chdc hon.
- Trdn kho: Id mdt qud trinh eat dit_ vd jrong qua trinh phut viia, cin khoan vira frdn vdi mdt ham lugng ximang kh6 bdng xoay vira riit len, tao thanh cot tron. Dudng tiiiet bi ludi dao quay, co thi cd hoac khong kinh toi da cua cot phu thudc vao dac tinh
46 j Journal of transportation science and technology. Vol 16. Aug 2015
cua hing loai dit. He so tham co the dat 10'''- 10-5 (cm/s).'
2. Phirong phap p h i n t u hihi ban (FEM - Finite Element Method):
Day la phuang phap phat ttien ciing vdi su phat triln ciia mdy tinh. FEM co the ldy chuyen vj niit hoac luc mit lam an sd. Trong do phuong phap chuyen vi la pho bi£n nhat.
Qua trinh phdn tich de giai theo phuong phap FEM nhu sau:
- Rdi rac hda mdi trudng hen tyc.
- Lira chgn mo thiie chuyen vi.
- Ldp ma frdn dg ciing, thiet lap phuang trinh cdn bdng
- Thiet lap he phuang trinh dai sd todn bg the lien tyc da rdi rac hda :
{K}{6}={R}
Trong do :
{K} : Ma fran do ciing tdng the {5} : Chuyen vi cua cac nut {R} : Tdi trgng tai nut
Dimg phuong phdp true tilp hay phucmg phdp thay thi d l gidi tim chuyin vi eua cac mit (chuyen vi la dn sd eua mit phin tir).
- Tti chuyen vi mit ta tim bien dang, ling suat cua phan tir kit cau than tudng cilng nhu ciia mdi trudng ddt,
Plaxis (Hd Lan) Id phdn mem ling dyng FEM frong ldp frinh. Trong pham vi bdi bao se sii dyng phucmg phap phdn tir huu ban 2 chieu de tinh (thdng qua phdn mem Plaxis version 8.5). Khi md phdng se dua theo cdc dac diem sau:
- Lira chgn md hinh cua dit : Bk tien trong qua trinh phdn tich va dl dang ttong viec nhap thdng so dau vao, tac gid se lira chgn md hinh Mohr Coulomb d l phdn tich.
Xac dinh frang thdi ban ddu: Theo ttang thdi thue tl ciia cdng trinh trudc khi dao h i mong, mo phdng gia tai d l tinh todn mgt Idn, thu duge trudng ling suit va xem dd Id trudng ung suit ban ddu.
3. D|ic diem cong trinh tinh toan:
Ham vugt sdng Sdi Gon Id mOt hang mue nim frong du an Dai Lg Ddng Tay -
TP. Hd Chi Minh. Ddy Id cdng trinh him vugt song ddu tien d Viet Nam.
Mgt frong nhiing hang muc quan frgng nhat frong qua frinh xdy dung ham Id thi c6ng tudng lien tiic frong dat. Trong qua trinh thi cdng cdc inclinometer duge bd tri frong than tudng giiip ta quan sat chuyen vi cua than tudng trong qua trinh thi cdng.
Tai vi fri tiep noi vdi ham dim chilu sau eua tudng Id ldn nhat vd su lam viec ciia tudng ciing phiic tap nhat, Khu vyc phan tich de cap frong bai bdo nay tir km 14+350 den kml4+365. Trong pham vi nay tudng duge gia cudng bang cgc ddt gia cd xi mang.
Md hinh hda viing ^t gia cirdng DSMC ben ngodi hd ddo trong Plaxis:
Cdng nghe dp dung d khu vuc nay la cong nghe frOn kho JMM, dudng kinh DSMC 1.2m. Mue dich gia cudng viing dit nay la nham gidm dp luc dit tac dung len tudng frong ddt. Vi tri nghien ciiu la vi tri sdu nhat ciia dudng ddn, ddy la khu vuc phiic t^p nhat.
De md phong viing dit ndy thi cin quy ddi cdc thdng sd tuong duong eho vung ddt duge gia cudng. Tuy nhien, ty le gia cudng vung dit nay gan nhu la 100% nen coi thong s6 viing dit nay la thong sd cua DSMC. Cu the nhu sau:
Bang 1. Cac chi tieu Cac chi tieu
M6 iiinh ifns xir v3t li|u Dung trpng tren
MNN Dung trong duai
MNN He so tham ngang He so tham dimg
Luc dinh Do gia tang luc dinh theo chiSu sSu
Goc noi ma sat Goc gian no Mo dun dan hoi
He so Poisson He so tuong tac giGa dat va Icet cau
cua DSMC
DoTi vi
lcN/m3 kN/m3 cm/day cm/day IcPa kPa deg deg liPa
-
DSMC MC
17.00
- -
1000
0 0 3.48E+05
0.2 0.75
TAP CHi KHOA HOC C O N G N G H E GIAO THONG VAN T A I , S O 16-8/2015
47
Ham ddn duge thi cdng theo cdng nghe Top-Down. Ttinh tu thi cdng co bdn nhu sau:
- Budc I: Xay tudng va cgc barrette, ddng he thdng king post.
- Bude 2: Dao lin 1 din cao do - 0,5m.
- Budc 3: Lap thanh chdng d cao do + 0,5m. Dao lin 2 din eao do - 4,5m.
- Budc 4: Ldp thanh chdng lin 2 d cao do - 3,5ra. Ddo lin 3 din cao do - 8,0m.
- Budc 5: Lap thanh chdng d cao dg - 7,0m. Ddo lin 4 din cao do - I I , I I m .
- Budc 6: Do betdng ban tren (Top-slap).
Ddo ldn 5 den cao do - I9,46m.
- Budc 7: Cdt he thdng king post. Dd betdng ban ddy (Bottom-slap).
- Budc 8: Dd betdng tudng giua (middle wall) va 2 tudng ben (side wall).
- Budc 9: Lip ddt va hoan thien.
Trong sudt qua trinh thi cdng theo trinh tu fren phai ludn dam bdo hd dao frong dieu kien khd rao. Do vay he thong gieng bom duge bd tri de dam bdo cao do mue nude ngam frong hd ddo luon thdp hon eao dg ban day.
4. Phdn ti'ch cac trudng hgp bdng FEM (Plasix):
De nghien ciiu vdn dl nay chilu sau va chilu rdng vimg dat gia cudng se duge thay ddi H=14m, 16m, I8m, 20m, 22m vd 36m;
tuong ling vdi be rdng vung ddt gia cudng W=6m, 8m, lOm, 12m, 24 bdi todn duge giai bang Plaxis. Cac vi du dien hinh:
Hinh 2. H^lSm. W=]2m K§t qua:
ffinh 3. Hinh dnh Icet qud tong chuyen vi Tru&ng hap gia cuang coc ddt xi mdng
Hmh I. H^14m, W=6m Hmh 4. Hmh dnh ket qud tong chuyen vi Tru&ng hop khong gia cuang
48 Journal of transportation science and technology, Vol 16, Aug 2015
B i o d i n cao do -4.Sm v i lap t h a n h chfing 1 I - - • na aac [hut i^ —-— Tinh bang Pbxa |
Bang 2. Tong hap kit qud mo men uon ldn nhdt vd chuyen v; ngang ldn nhdt cua tuang chan kht co va khong CO gia cu&ng DSMC theo phdn tich bdng
PTHH
O l 0
'' '
"
"
lU
••
^ f r
„J . i . 00, ., 1 ; •' !
\-' / I 1/ '
•* / 1
; . ,/ ,
/ 1 ' .
/
i •) -
;j 1 1 1 1
*\
Hinh 5. Bieu do so sdnh chuyen vj ngang ciia ttr&ng
i
giua quan trdc thue te vd ket qud phdn tich bang PTHH
(Khi ddo den cao do -4.5m) D i o d^n cao d$ -11.0m v^ lap thanh chong 3
[01 , 0
-w^
X) 0 1 n
= h u y *
12 D
• I — ™ ! "
nrr i.^'
.)
1)5 O 0 6 0
1
17 O p 8
•;•
I-/ 1
>
,
• ' ;
L ^ f)
, 1
i
' /^
) ; •
J ;
i
TT
i
1 1 ,
' 1WJnA 6. Bieu do so sdnh chuyen vi ngang ciia ludng giira quan trdc thirc te vd kit qud phdn tich bdng
PTHH (Khi ddo den cao do -}!m)
Kich thuac vung gia
cudng (HxW) Khdng DSMC 6x14m 6x16m 6x18m 6x20m 6x22m 6x3 6m 8xl4m 8xl6m 8x18m 8x20m 8x22m 8x36m 10xl4m 10xl6m lOxlSm 10x20m 10x22m 10x36m 12xl4m 12xl6m 12xl8m 12x20m 12x22m I2x36m
Ket qua tinh toan Mo men
max (kN.m) 2627,76 2152,20 2223,63 2237,97 2220,58 2251,57 2182,14 2105,07 2202,00 2303,31 2289,61 2272,19 2176,91 2117,77 2241,73 2158,30 2151,77 2132,34 2124,68 2150,69 2290,22 2414,64 2405,31 2385,61 2264,50
Chuyen vi ngang max
(m) 0,0684 0,0419 0,0387 0,0357 0,0354 0,0373 0,0346 0,0370 0,0343 0,0320 0,0317 0,0315 0,0280 0,0341 0,0310 0,0284 0,0281 0,0279 0,0247 0,0318 0,0286 0,0259 0,0255 0,0253 0,0223 Vung gia cudng DSMC kich diudc (H=10m, W=18m) Id trudng hgp duge sii dyng frong thue t l thi cdng dudng dan cua ham Thu Thiem do nha thdu Obayashi Corp.
(Nhat Bdn) thue hien.
TAP CHl KHOA HOC C O N G NGHg GIAO T H O N G VAN T A I , S O 16-8/2015 49
Bang 3. Tong hgp mirc dp gidm chuyen vi ngang vd mo men uon ciia iir&ng trong ddt khi co gia cudng bdng DSMC so vdi trudng hap khong gia cudng
Kich thiro'c viing gia
cirong 6x14m 6x16m 6xl8m 6x20m 6x22m 6x3 6m 8xl4m 8xl6m 8x18m 8x20m 8x22m 8x36m 10xl4m 10xl6m lOxlSm 10x20m 10x22m 10x36m 12xl4m 12xl6m 12xl8m 12x20m 12x22m 12x36m
Ty le (%) tang/giam so vol khong gia curmg Mo men
uon -18,10 -15,38 -14,83 -15,50 -14,32 -16,96 -19,89 -16,20 -12,35 -12,87 -13,53 -17,16 -19,41 -14,69 -17,87 -18,11 -18,85 -19,14 -18,16 -12,85 -8,11 -8,47 -9,22 -13,82
ChuySn vi ngang -38,74 -43,42 -47,81 -48,25 -45,47 -49,42 -45,91 -49,85 -53,22 -53,65 -53,95 -59,06 -50,15 -54,68 -58,48 -58,92 -59,21 -63,89 -53,51 -58,19 -62,13 -62,72 -63,01 -67,40 5. K i t ludn:
Tii kit qua tinh toan ta ed the thdy ro tdc dyng cua viee gia cudng viing ddt phia ehu ddng ciia hd dao sdu bang DSMC, do Id:
- Gidm tihanh chuyen vi cua tudng.
- Giam md men ndn ciia tudng Ta thay rang chuyen vi cua tudng giam nhieu nhat la 67,40% vdi kich thudc viing dat gia cudng 12x36m va nhd nhdt la 38,74% vdi kich thudc viing gia cudng 6x14m; Md men
uon ciia tudng gidm 19,89% vdi kich thudc vung gia cudng 8xI4m vd nho nhdt Id 8,11%
vdi kich thudc vung gia cudng 12x18m. Day la mgt ty le giam rat Idn chiing td tac dung ro ret eua viec gia cudng vung ddt phia chu dgng ciia hd dao. Nguyen nhdn lam giam chuyen vi ngang ciia tudng la do viing ddt gia cudng se gdnh chiu phdn Idn dp luc ddt tac dung len tudng.
Vdi ket c^ua tinh todn fren ta thdy rdng kich thudc tdi im vung gia cudng frong trudng hgp dang xet Id vao khoang 10xl8m.
Vi vdi kich thudc ndy chuyen vi ciia tudng da giam den 58.48% bdng 86.77% miie giam chuyen vi ldn nhdt; mo men gidm 17,87%
bang 89.82% miic giam mdmen ldn nhdt. Tir kich thudc nay frd di thi tac dung giam khdng nhieu. ¥M qud ndy la rdt phu hgp vgi thue te thi cdng da duge nha thdu Obayashi Corp. tien hdnh tai hang myc hdm ddn Thu ThiemQ
Tai lieu tham khao:
[1] Obayashi Corporation (2007), "Method Statement For Tnal Column For Soil Improvement At Cut & Cover Tunnel Tt Side"
[2] Obayashi Corporation (2007), "Method Statement For Soil Improvement At Cut
& Cover Tunnel Tt Side"
[3] Obayashi Corporation (2006), "Method Statement For The Excavation of Cut &
Cover Tunnel At The Thu Thiem Side Tunnel Approach"
[4] Obayashi Corporation (2007,2008),
"Monitoring At Thu Thiem Side Tunnel Approach - Inclinometer Data Sheet"
[5] Obayashi Corporation (2006), "Method Statement For The Installation of Relief Well For Cofferdam At The Thu Thiem Side Tunnel Approach"
[6] Bachy Soletanche (2005), "Method Statement For Diaphragm Wall &
Barrette Piles Construction Thu Thiem Tunnel Cut & Cover".
Ng^y ohSn bdi:
Ngdy ch^p nh$n dang:
Phanbifn: TS. Nguyin Khanh LSD TS. Nguyen K I Tirfrng
