##### KHOA HOC - CONG NGHE
NGHiEN CljrU, PHAN TICH GIA CO NEN DAT YEU DU0I NEN DirdNG BANG COT DAT TRON XI MANG
TS. L£ BA VINH eg/ hgc Bdch khoa Tp.HCM KS TRjNH DUY HAI Tdng Cdng ty diu twphdt tnin & qudn If
dl/ dn hg ting giao thdng Ciru Long THS, NGUY6N TAN BAO LONG Dg/ hgcTiin Giang
Tdm tit: Hiin nay viic thiit ki, tinh todn, cDng nhw thi cdng cdt dit trdn ximdng <3i gia c6 cho nin dit yiu hiu hit diu tham khdo, si/ dicing cdc qui trinh, cdng nghi cua nirdc ngodi nhw Tht/y Diin, Nhdt Bdn,... Tuy nhlin cQng cd mdt s6 vin di vi cdch thiit ki, tinh todn theo cdc qui trinh ndy. Bdi bdo ndy dl sdu phdn tich di di xuit cdch thiit kS hop ly chiiu ddi cdc cdt dit trdn ximSng di gia cd cho nin dit yiu dirOi nin du^ng. Ngodi ra. bdi bdo cOng phdn tich vi cdch xdc dinh dd lun 6n djnh cua nin dit gia c6 bing cdt dit trdn xlmdng, tiin hdnh phdn tich ngirgv; dd lun quan trio cua nin dit gia c6. Viic phdn tich, tinh todn du^ tiin hdnh cho cdng trinh ci/ thi Id D^i Id Ddng - Tdy.
Abstract: The deep mixing method has been widely applied to reinforce the soft grounds for many kinds of project in Viet Nam. The designs of this method are usually referred to some foreign standards.
However, there are some existing problems of the calculation. This paper analyses the method of settlement calculation, and proposes the change of soil-cement columns length to reinforce the soft grounds under embankments.
1. Gidl THIEU
Giai phap CQt dat trOn ximSng de gia CO cho n^n dit y6u da dii-QC nghi§n ci>u i>ng dgng nhilu a tr^n the gic^i. Q Vi$t Nam giai phdp ndy da diTQC si> dgng ngay cdng nhieg trong thd-i gian g4n ddy cho nhi^g io^i Cdng trinh ithdc nhau;
Dgi 10 Dong - Tdy, kho xdng dciu Nhd Bi. khu VTnh Trung Plaza, v.v... VIQCthilt l<l, tinh todn, cOng nhif thi cdng cOt dit trOn ximdng a l gia c6 cho nln dit y l u hiu hit diu tham l(hao, sg dgng cdc qui trinh, c6ng ngh$ cOa nu'dc ngodi nhu Thgy Oiln, Nhdt Bdn, Trgng Qg6c, ... Tgy nhiSn cDng cfi mjt s6 v i n de ve cdch thilt ke. tinh todn theo cac qui trinh ndy. Phin dg6i ddy trinh bdy vi^c phdn tich, vd d l xgat cdch tinh todn hi^p ly cOt d i t trOn ximdng d l gia co cho nln d i t y l u dgdi nln dg&ng.
2. PHAN TiCH, TiNH TOAN COT DAT-XIMANG D^ GIA CO N^N CHO CONG TRiNH THITCTf 2.1 GIIII thieu vicing trinh
Trong phin ndy tiln hdnh phdn tich giai phdp gia c6 nln d i t y l g dgdi nln du'6'ng cdng trinh Dsi 10 D6ng - Tdy thujc khu vi,rc Qudn 2 Tp. H i Chi Minh blng cOt d i t - xi mdng.
2.1.1 s6 ll$u v l c6ng trinh dir6ng S6 li^u nln du'6ng dip nhu"
sau; chilu cao nln dgimg d i p
^nt^ - '••''"'. ^^ 'i"9 n^" dgb'ng B,*, = 24m, dO die mdi taluy 1;
1.5, d i t d i p c6 y = 1.815g/cm'.
TrSn mjt du'b'ng c6 hQat tdi xe chgyld15.22kN/m=.
2.1.2 S6 li$u d{a chit c6ng trinh Theo ket q u i khao sat dja chit cing trinh [4] phgc vg cho cdng
M iilKll
tac thilt k l ky thgdt thi d n g cong trinh "0?i 10 DOng - Tdy" cho thay d|a ting khu vg'c tir mdt dit xuIng din dO sdu khdo sat Id 30m dir?c phdn thdnh cdc Idp nhg sau;
1/ LOpdlt s6 1; Bun s^t hiru CO, mdu xdm ghi den din xdm xanh nhgt, trgng thdi rit mim, bk diy 20m
2/ Ldp dit s6 2; S6t pha nliieu cdt, mdg xdm ghi den din xdm xanli nhgt, trgng thdi mim, b l ddy 10.0m 2.1.3 S l liOg cOt dit - ximang cot d i t - xi mang vOi cdc kich thu'd'c CO' bdn nhg sag;
- Chilg ddi CQt d i t xi mdng A tim dgdng, L^, = 20.0m;
- DgOng kinh cOt dit xi mSng, d = 0.6m;
- Khoing cdch giOta hai cOt ke nhag, s = 1.5m;
S67nsm2012|
KHOA HOC - CONG NGHE # # # # #
-Blrpngbotricdttheophuong B A N G 1: Cac chi tidu c v ly cua cdc 16'pdltnln ngang dud-ng, B =33.6 m
Mo dun bien dang cua cOt dat- xi mdng: E^, = 73856 kN/m^
Cud-ng dp khdng cat eua cdt dit-xi mdng- C ^ , = 269,2 kN/m^
2.2 Nghien cDU ttiiet l(^ liap I j chieu dai cua cdc cot dat - ximang
Khi thiet k l gia c l nln blng cae cdt dat - ximdng cho nln dudng thi d l don gian vd nhanh chdng khi thiet k l ngudi ta thudng b l tri hd cdc cdt dat - ximdng cd chilu ddi diu nhau. Tuy nhidn, khi cd tai trpng nen ddp tdc dgng Idn hd thong cpt dit - xi mdng thi su phdn b l ung suit vd anh huong eua tai trpng nln dap theo chilu sau cpc thay doi va giam din theo hud'ng xa tim dudng. Do vdy, khdng nhit thilt phai bo tri hp cdc cot dat - ximang cd chilu ddi diu nhau. Q day cd the nghien cuu su thay dii ung suat ndy nham b l tri hp thong cae cpt hpp ly de dem lai giai phdp gia c l cd hidu qua kinh t l nhit.
Cdc chj tieu co* li 0 0 I m t y nhifin W Dung trong y d t Y,„
Dung trong d i y noi y^^
H? s6 r i n g e,, Ap lgc tien c6 k i t Chi s6 nfin C^
Chi so n d C, Lgc dinh C Gdc ma sdt trong (p
D a n vj g/cm^
(%)
g/cm^
(kG/cm')
(kG/cm')
eo
L d p 1 82 5
1.5 0.61 2.14 0.62 0.958 0 168
0 06 3°40'
2 25.23
1.92 0 96 0 7 5 2 2 87 0.061 0 009
0 12 18-13'
C o c XM-DaV
I 2 3 4 5 6 7 8 9 1 0 I I 1 2
Hinh 1.
So 66 bo Iri cac c6t dat- ximSng (cho '/; cong trinh)
2.2.1 Phu'cng phap xac djnh 2.2.2 Phdn tich, tinh toan cu Bao gIm edc budc nhu sau
- Voi thilt k l ban dau hp cdc cpt dat - ximang cd chilu ddi nhu nhau: tiln hanh tinh todn si/ phdn bo ung suit bdng phin mim Plaxis 2D tai dilm giQ-a cdc dau cpt theo phuong ngang. Cdc gid trj ung suit duoc lap thdnh bang va t h l hidn thdnh bilu do tuong quan.
- Ve dud'ng cong phdn b l ung suit theo phuong trinh xac l^p o"
budc tren, su dyng dud'ng cong ndy thilt ldp mli quan he gii>a chilu sdu t i i thilu va vi tri cua cdc cdt tuong O'ng.
the
Tiln hdnh phdn tich, tinh todn cho cdng trinh cy t h l Id Dgi 10 Dong - Tdy ndu trdn
• Tinh todn sy phdn b l ung suit tgi dilm giua cdc diu cdt theo phuong ngang
Vd'i thilt k l ban diu h$ cdc cdt dat - ximang cd chilu ddi nhu nhau, va dup'c danh so thu ty nhu trong hinh 1.
Diing phin mim Plaxis 2D tinh dup'c su phdn b l i>ng suat trdn cac cpt dit - ximang nhu trong bang 2, vd duoc bilu diln thdnh d l thl nhu hinh 2,
B A N G 2 . K i t qud tinh toan ung s u i t t^i cac cdt ddt ximang theo Plaxis 2D
S6 hieu cOt c o t so 2 c o t s6 3 c o t so 4 c o t s6 5 c o t so 6 c o t so 7 c o t so 8 c o t so 9 c o t so 10 c o t so 11 c o t so 12
LTng s u i t ( kN/m') D i u cdt
263 98 256.96 271.90 260.49 243.01 215.66 143.42 139.28 129.11 119.18 72 760
GiOa cOt 7 6 0 0 1 7 6 2 0 4 764.43 758.30 719.38 668 85 621.90 570.08 498.83 423.77 368 88
I S6 7 nam 2012
©OSTMl®
##### KHOA HOC - CONG NGHE
Trong d d x: Id khoang cdch t u tim cpt d i n tim d u d n g theo p h u o n g ngang
* Xdc djnh s y gidm c h i l u ddi cua cdc cdt d i t - ximdng theo p h u a n g ngang d u d n g
Sau khi vd d u p c d l thj gidm u n g s u i t t u tim ra d i n mdp n l n dud'ng ta tinh d u p c dd giSm u n g s u i t tgi cdc c | t . T u dd tinh d u p c d d giam c h i l u ddi cua cdc cOt n h u trong bang 3.
* K i l m tra Igi I n djnh vd b i l n dgng cua n l n dud'ng sau khi b l tri cdc cdt d i t - ximdng cd c h i l u ddi gidm theo p h u o n g ngang d u d n g
Sau khi tinh dup'c dO gidm c h i l u ddi cdc c$t ta ed t h l b l tri Igi theo p h u o n g ngang vd tinh todn, k i l m tra s y I n dinh vd b i l n dgng eua n l n dud'ng bang Plaxis 2D n h u hinh 3 vd hinh 4
V d i hp s l an toan tinh dup'c la FS = 1,257 vd dp lun tgi tim dud'ng la 33,1cm cd t h l thay r i n g trud'ng hp'p b l tri cdc cdt d l t - ximang vd'i c h i l u ddi gidm theo p h u o n g ngang d u d n g n h u trdn vdn dam bao cdc dieu kipn I n dinh vd b i l n d$ng.
X(m)
7,5 0 10.5
" /
!
1
1
1
1
1
1
Hinh 2.
B i l u d l t h l hi$n s y gidm Crng suit theo phuang ngang dudng
1
'
7 a 1
,
Wl-Ddt
Hinh 3.
B 6 tri cdc cot lit- ximdng vdi chtlu ddi gidm theo phgang ngang dirdng
J?3W<x,
; . K ;
BANG 3 Ket qua tinh todn thay e6\ c h i l u ddi cOt
Ky hiOu cot X ( m ) ACT^ (kN/m=) Aft^ (m)
cot si 2
1.60
430
0.87
cot
s6 3 3.00 81 0 1.60
cot
s 0 4 4.50
114
2.33 c o t so 5 6.00
144
2 90 c o t s 6 6 7,50
170
3.58
cot
s 0 7 9.00
193
4.28
cot
s6 8 10.50
214
4.48 c o t s 6 9 12.00
232
5 40
cot s l i o
13.6
248
6.73
cot
s 6 l l 15.0
262
8,63 Cgt so 12 16.5
275
9.31
^m
So 7 nam 20121KHOA HOC - CONG NGHE #####
3. Phan tich, de xuat each tinh toan do iun cua nen gia
CO
Theo TCXD 385:2006 [3], trong trud'ng hp'p A, dp liin cua nln dit la:
S=Ah,+Ah2
Dd lOn cue bd phin cpt dlt- ximang Ah, dup'c xdc djnh theo gia thiet dp tang ung suit q khdng dii suit chilu cao khIi vd tdi trpng trong khIi khdng giam:
H*q
^h =- (8)
a * £ : „ , + { l - a ) * £ , „ , Trong dd: a. Didn tich tuong doi cua cpt dat-ximang
E^ vd E ^ lln lupt Id md dun biln dgng eua cpt dat-ximang, va cua dit
Dp lun Ahj duoi ddy cdt dit tinh theo phuong phdp cdng ldp phan t l .
Vd'i cdch tinh neu tren thi khong xet ddn ung suit phy thdm do trong lup-ng ban than cua cpt dat-ximang.
Vipc tinh todn dd lun I n djnh cCia phin nln dat dupc gia c l bdng eac edt dit xi-mdng cd dya vdo mdt s l gia thilt don gian hda nhu tren, do vdy kit qua tinh lun theo cdng thCpc ndy co t h l cd sy khdc biet so vd'i dd lun thye t l . Nhdm khao sat sy khac bipt ndy, phin mim Plaxis da dupc su dyng d l tinh todn dd liin Ah, cua phan nln dit dup'c gia eo.
Bdi todn khao sat eung giing nhu cdng trinh dd ndu d" myc 2., nhung trong dd Id-p dit so 1 se lln lupl dup'c thay t h l blng mpt logi dit khde trong 4 trud'ng hpp khac nhau nhu md ta d bang 4.
Cdc kit qua tinh todn dp lun
-^ A k
Hinh 6.
M6 hinh tinh todn ICin trud'ng hop A
B A N G 4. Bang thong s6 tinh toan dp lun theo cac tru'O'ng hp'p cua Id'p 1.
STT 1 2 3 4 5
Trudng ho'p cua Idp 1 Bun nhdo S6t deo m i m 1 S6t deo mem 2 S6t deo m i m 3 S6t deo cdng
lulodule bien dang E^,,
(KN/m^) 1060 2761 3022 3112 4165
Dung trong (KN/m>)
16.1 18.58 19.07 18.65 19 2
Lgc dinh (KN/m')
6 10.7 12 5 14 5 19,4
Gdc ma sdt (p (") 3,67 12 75 13 25 14 13 75
BANG 5, K i t qud tinh todn dQ lun theo tCmg tru'O'ng h^p cua ldp 1.
STT
1 2 3 4 5
Truvng hp'p cua Idp 1
Bun nhao Sdt deo m i m 1 Sdt deo m i m 2 Sdt deo m i m 3 Sdt deo cdng
Dg lun Ah^ (cm ) Tinh theo
TCXD 385:2008 17,2 , 15.9 14 7 14 6 1 3 6
Tinh theo Plaxis
17.8 13.0 1 2 4 12 3 8 3
Sai s d (%) 3.46 1 3 4 4 15 82 15.95 38.93
I S6 7 nam 2012
# # # # # KHOA HOC - CONG NGHE
theo TCXD 385:2006, vd theo Plaxis eho tung trud'ng hp'p dup'c ting hpp nhu trong bang 5 [2].
' Nhdn xdt cdc kit q u i tinh todn'
Vdi trudng hpp 1 (dit bCin nhdo) thi kit qua tinh liin theo hai phuong phdp hiu nhu giing nhau. Nhung v6i 4 trudng hpp cdn Igi thl kit qud tinh ICin theo TCXD 385:2006 Id Idn han ddng k l so v6i kit qud tinh lim theo Plaxis,
Mdt trong nhOng ly do Id cdng thuc tinh lun theo tidu chuin tuong ty nhu djnh lu^t Hooke.
- -'^''' - _£_
Vi t h l khi tinh ICin theo tidu chuin da khdng xet din dp lyc hdng xung quanh khli gia c l do SLPC khdng cit C^, eua dat nln tgo ndn, Phin mim Plaxis khi tinh lun da c^ xet din lyc ma sdt thdnh nay ndn Idm giam dp lun. Cdc trud'ng hp'p dat nln cd lyc ma sdt thdnh cdng Idn thi sai s l dp lun giua hai phuang phdp tinh trdn cdng Id-n
Do vgy nen b l sung lyc ma sdt thdnh ndu trdn vdo cdng thuc tinh lOn theo tidu chuin.
4. DO LIJN THEO THOI GIAN CdANENDATDirOCGIACO
Tgi hdi nghj khoa hpc Ddng Nam A lln thu 15 chuydn ngdnh Oia K? Thu$t tgi Bangkok-Thdi Lan vdo thdng 11-2004, D.T Bergado dd trinh bdy v l v i n d l lun c l kit cua khli dip trdn nln d i t cd gia c l blng cdt d i t - xi mdng. Theo dd D.T. Bergado cho ring h | s l thim cua cdt d i t XI mdng blng khodng 30 lln h$ s l thim cua dit sdt ty nhidn (k^p = 150x10-1° . 200x10-'° m/
gidy; k^ = 3x10-'°-6x10'°m/gidy) tuong ung vdi dO idn c l kit cua nln sau 1 ndm Id S = 350 (mm).
Kit qua trdn nhdn dup'c tu phdn tich gidi tich kit hpp vdi phuong phdp Asaoka, ding thdi dupc kilm chCrng blng phuong phdp s l vd thl nghidm trong phdng,
Thi nghipm hi$n trud'ng dup'c D,T. Bergado thye hidn tgi qudn Wangnoi - Ayathaya - Thdi Lan (2002). Theo dd thi 63 cOt d i t XI mdng cd dud'ng kinh 06m dupc thi cdng theo bidn phdp Jet grouting sdu din 9m trong nln sdt yeu. Hdm lup'ng xi mdng la 150kg/m' dit, q^ = 300 - 700 kPa, E „ = 60-120 Mpa.
Trong phin ndy cdc tdc gia si> dyng Plaxis 3DF phdn tich ngupc tu dO liln c6 kit thu dupc tu quan trie hidn tru6ng cua D.T Bergado 6h kilm chung ty Id giOa h$ s l thim cua cOt dit xi mdng vd h$ s l thim eua d i t y l u .
4.1 Mdhinh Vd cdc thdng stf v$l Mdu trong Plaxis:
B A N G 6, Cdc thdng s d ctJia md hinh thi nghidm gia c6 nln blng c^t d i t - ximdng.
&1ATEIUAU S.l»»fl 0 - 2 } n i 2 J - 9 n i 9 - n m n - 1 6 n E i d u k a m IInj|<iii>l Wir< Ufih Coacrek Ficii^
Soil- CinuDl Pil(
DESCSIPIION
W«ttwKd Cnur Soflcliy Mednmliuffcliv
Stiff cbv Siltyiuid RdnfiHronnu CoDcrcte bdng DMMpile
MODEL
HSM SSM HSM HSM MCM EM EM MCM
{kNTn*l
16 14.7 lJ.i 17,0 20
(kPi)
16 i : 60 100
OCR
9 1,5
;,o li
fliPi)
i~«
0 1-4 1-10 1-S
*
23 23 23 23 ID
X'
0 1 2 - 0.16
K-
0,02- 003
ftP»)
2500 330 3000 4700
»D0 V
0,25
025 OJS 030
0.00005 OJJOOO)- OOOOIS 0 0 0 0 0 5
0-ODOOl Dm.
AE - 9D0 LNtai; mlh iiitB&Ec dcmaiB ir both udci, R ^ = 0 J A£ - 1200000 kN/m. EI- ZTOkN-rnVm
IS 1 300 j 1 300 1 28-30 1 1 [ ' j ^ ^ ^ ' 1 0_JJ j K v » ^ M
®i)@IHI@
S6 7 nam 2012 IKHOA HOC - C O N G NGHE gMM0§
T (thang)
10 12 14 16 18 20 22 24 26
—•—Ouanlrachi^n trLT^ng -•--PlaKisBDF
Hinh 8. D l thj bilu di§n k i t qua ICin c l k i t cua cdc phuang phdp
4.2 U\ qud tinh todn dd liin theo thdi gian
Nhgn xet:
TCr d l thj trdn ta thay, phuong phdp phan tu huu hgn (Plaxis 3DF) phan tich lun theo thd'i gian cQng khd chinh xdc, sai Ipch Idn nhat so vd'i quan trie hidn trudng la 6,4 cm. Sai lech ndy la khdng ddng k l va cd t h l Id do phan mim khdng t h l md ta ehinh xdc qud trinh chat tai so vd'i thye te ngodi hien trud'ng.
Theo nhu kit qua phdn tich ngupc blng Plaxis, cd t h l nhgn thiy: vd'i cac thdng sd vdt lipu nhu tren thi he s l tham cua cdt dat tr$n xi mang bdng khoang 15-20 lln he s l thim cua dit ty nhien.
5.KETLUANVAKIENNGHJ Qua vipc nghien cuu, tinh todn cpt dit Iron xi mdng d l gia c l nln dit ylu cho cdng trinh Dgi 10 Ddng - Tdy cho phdp rut ra cdc nhdn xdt, kit ludn nhu sau:
CO t h l thilt k l chilu ddi cdc cOt dat - xi mdng giam theo phuong ngang dud'ng. Cdc cdt
nim cdng xa trye tdm cua nln dudng thi chilu dai cOt cdng gidm, B l tri chilu dai cdt giam theo phuong ngang dudng ed b l rpng Id'n cd t h l Idm giam ddng k l ehi phi gia c l nln, nhung van dam bao cdc ydu cdu v l I n djnh vd biln dang.
Sai s l ve kit qua tinh lun theo TCXD 385:2006 vd theo Plaxis dii vdi cdc trud'ng hp'p dup'c tinh Id ddng k l , Id'n nhat len din 38.93%.
Cdng thuc tinh lun theo tieu chuan tuong ty nhu djnh lugt Hooke Id khd don gian. Vi t h l khi tinh lun theo tieu chuan dd khdng xet din [ye ma sdt xung quanh khli gia eo do dit nln tgo nen Do dd tgo ra sy khdc bidt giOa kit qua tinh lun theo tieu chuin vd theo thye t l .
Cdc kit qua tinh cho thiy dit nln cd si>c ching cat cang Idn thi sai s l dd lijn giOa hai phuong phdp tfnh tren cdng Idn. Do vgy nen b l sung luc ma sdt thanh ndu tren vao cdng thi>c tinh lOn theo tieu chuan
Theo nhu kit qua phdn
I
tich ngupc blng Plaxis thi hp s l thim cua cpt dit trpn xi mdng blng khoang 15-20 lan he s l thim cua dat ty nhiena
TAI LIEU THAM KHAO 1 D.T Bergado, J.C Chai. M.C
Alfaro, A. Baiasubramaniam, Nhung bi#n phap ky thuat mdl cai tao dat yeu trong xay di,mg. NXB GiSo dye. 1993.
2. Nguyen Hoai Duy. Nghien CCKU gia c6 n4n dat yeu duoi nen du'O'ng blng cpt d i t trOn xi mang lai Ogi 1$ Dong- Tay khu vyc qu$n 2 Lu§n vSn thac sT OH BSch Khoa Tp Ho Chi Mmh, 2009
3, TCXDVN 385: 2006, Phu'CTng phap gia c6 n^n dat yeu bang try dat xi mling, BO X§y Dyng, 2006.
^. Trung t3m Rectie, Bao cao dja chat cong trinh Dgi Ip Dong- TSyth^ng 11-2007
