PHAN TICH ON OjNH NEN MONG CONG TRINH BEN CAU TAU DUOC XU* LY BANG MONG COC BE TONG
COTTHE'P KET H O P C O T M T T R O N XI MANG
Tran Xuan Tho Tran Thanh Trung
ABSTRACT
This paper is aimed at analysing the stability of foundation of the landing pier on the soft soils treated by the concrete piled foundation and soil-cement deep mixing columns. The soil-cement deep mixing column is applied to improve the soft soil in order to increase the stability of slope failure, to reduce the differential settlements between the wharves and the internal road base and to limit the horizontal displacement of overground pilework foundation of landing pier.
Keywords: Landing pier, piled foundation, soil-cement deep mixing column, stability.
TS Tran Xuan Tho - Khoa xay dung Trucmg DHBacli khoa TP.HCM Email: [email protected], Di dong: 0908.155.131 Th.S Tran Thanh Trung Cong ty co phan t u van xay dung Ben Tre
Email: trungbcdisyahoo.com.vn Di dong: 0913.133.849
1. Oat van de
Hien nay cac cong trinti ben cau tau d cac cang tiiupc khu vUc Bong bang song CCru Long deu dUcfc xay dUng tren nen dat yeu hoac rat ye'u. Do boi lang, nen khi xay dting cac cong trinh ben cang vdi tai trpng ldn thudng phai nao vet rat sau va ket hpp vdi qua trinh xoi mon. Oieu nay dan den sif mat on dinh cong trinh do trUcn. sau va chuyen vj ngang Idn trong suot mpt thdi gian dai cua qua trinh thi cong va khai thac sCr dung. Khi danh gia mu'c dp on dinh cong trinh can phai xet den tac dpng tuong ho dong thdi giUa cong trinh va nen dat. Giai phap gia co nen bang cpc dat xi mang dupc de xuat nham tang kha nang chong trupt (khi dupc gia co vdi dang tudng chan) va han che lun lech giUa phan tiep giap giufa phan nen dUdng, kho bai ben trong vdi cong trinh ben (khi dupc gia co vdi dang cpt theo ludi 6 vuong hoac tam giac), giam thieu kha nang chuyen vi ngang cua he mdng cpc be tong cdt thep, dong thdi co the rut ngan dUpc thdi gian thi cdng cdng trinh. d day, cong trinh Ben cau tau khu vUc Cang Giao Long-Ben Tre dupc ap dung de nghien cUu.
2. Gidi thieu cdng trinh Ben cau tau 2000DWT trong dU an Cang Giao Long - Ben Tre
Cang Giao Long cd dien tich 43,13ha thupc huyen Chau Thanh, tinh Ben Tre cd vai trd van chuyen may mdc thiet bi, vat tu, vat lieu phuc vu qua trinh xay dung va san xuat cua cac doanh nghiep trong khu cdng nghlep Giao Long, khu cdng nghiep An Hiep va cac khu cong nghiep khae tren dia ban tinh Ben Tre. Cang song Giao Long dUpc xay dung nham phuc vu cho cac tau thuyen va sa lan cd tai trpng 2000DWT. Mat cat cong trinh cau tau dupc bieu dien dHinh 1.
Giai phap ky thuat cho cdng trinh Nen dudng san lap cao 1 m, phan ca'u tao ao dudng cd be day 1 m.
Phan nen tiep giap vdi ben dupc gia co
khoi dat xi mang cd be rdng 3m dpc theo suot chieu dai ben. Khoi gia co nay co tac dung nhit mpt tudng chan dat. Chieu sau cua khoi gia co la 15m (gia cd den Idp dat set pha trang thai nUa cUng).
Ben trong nen dudng dUPc gia cd b^ng cpc dat xi mang vdl dUdng kinh 1 m cung vdi chieu sau la 15m. Khoang each giiJa cac coc dupc tinh toan la 3m va bo tri theo lUdi 6 vudng.
3. Thi nghiem xac djnh sufc chong cit hufu hieu va ham lifcrng xi mang tron phu hop cho loai dat biin set
3.1 Ket qua thi nghiem cac thong so ddt nen tdthinghiem
Can cU vao bao cao ket qua khao sat dia ky thuat, khu vUc xay dung cd dac diem dia chat nhusau:
Ldp 1: Bun set, xam nau den, trang thai chay (0-15m), y^^^^, = 14.8kN/m^ y,,, = 14.9kN/
m^ c' = 8.3kN/m" cp' = 23°04', E^/'= 3881 kN/
^2 E '^' = 893kN/ml
oed
Ldp 2: Set pha, hong lan vang xam, trang thai deo cUng den nUa cUng (15-20m), y^,^^^, = 19.5kN/m^ Y^^, = 19.9kN/m^ c'= 23.4kN/mrq>'=
25037; E ref ="9304kN/m^ E /•" = 6481 kN/ml
50 ' oed
Ldp 3: Set, nau do lan hong, trang thai nira cUng den cUng (>20m), y^^^^^^ = 20.5kN/m', y^,
= 20.7kN/m3, c'= 35.1 kN/m" (p'= 25°58', B^^''=
7930kN/m^ E^^/''= 12598kN/ml
3.2 Ket qua thi nghiem nen nd hong mau ddt trpn xi mdng bang phiiang phap trpn Udt
Mau dat bun set dupc lay tUdp sau 5H-15m tai cong trinh, dupc trpn vdi xi mang theo phupng phap trpn Udt vdi cac ham lUpng 200, 220, 250kg/m', sau do tien hanh thi nghiem nen nd hdng. Ket qua thi nghiem dUpc cho trong Hinh 2 va Bang 1.
Vdi ket qua thi nghiem tren, ta lUa chpn ham lupng 200kg/m= (13%) cho giai phap gia cd nen bang cpc dat xi mang.
4. Mo phong tinh toan
Phan tich tinh toan on dinh cdng trinh
5 4 SiEiniEiffil 05.2011
coc DAT XI M A N G Bd' CQC OAT XI MANG 8Q TBt DANG nCWG CHAW TBI DANG 0 VUlKG
Hinh 1: Mat cat cong trinh cau tau 2000WDT
1.6 2.4 3.2 4.0 Bi^nd^ng - Strain, %
2084
a je 1667
w 1250
• =
a 834
417
/
/
^
•f \
J "\
/ \
;. . . ^
0.0 0.7 1.3 2.0 2.6 3.3 39 Bl6n d^ng - Strain, % J
Hinh 2: Quan he giufa u'ng suat nen va bien dang v6i cac ham lUclng 200,220,250kg/m'
thong qua phan mem Plaxis. DUa vao dac diem 2D bang phan mem Plaxis 8.2 (Hinh 3) va md dia tang va cac dac trUng cP ly cua nen dat yeu d hinh bai toan khdng gian 3D bang phan mem Dong b^ng sdng CUu Long, md hinh Hardening- Plaxis 3D Tunnel (Hinh 4).
Soil dupc sUdung trong tinh toan.ThUc hien tinh Trinh tutinh toan dUpc md phdng theo cac toan theo hai md hinh: Md hinh bai toan phang bUdc sau:
Budc tinh toan BUdcl BUdc 2 Budc 3 BUdc 4 BUdc 5
Noi dung thifc hien Thi cdng coc dat xi mang
Nao vet Idng sdng Thi cdng ben cau tau Thi cdng nen dUdng Tai trpng khai thac sU dung
Thdi glan 30 ngay 30 ngay 120 ngay 30 ngay 360 ngay
Hinh 3: M6 hinh tinh toan 2D Hinh 4: Mo hinh tinh toan 3D
5. Ket qud phan tich
5.7. Tuang quan dp lun ciia cau tau va ddt nen theo thdi gian
Dp lun lech giUa cau tau va nen dUdng theo thdi gian khi gia co nen bang cpc dat xi mang la 160mm dUpc md t^ d Hinh 5. Neu sU dung bangdemcatthiddlun lech giUa cau tau va nen dudng la 600mm nhU Hinh 6.
5.2. Cfng sudt phan bo trong nen ddt Lfng suat Idn nhat tac dung len dat nen dudi mui cpc: 1234kN/ml
Cfng suat nhd nhat tac dung len dat nen dudi mui cpc: 420kN/ml
Lfng suat trung binh tac dung len cpc dat xi mang: 164kN/ml
Lfng suat trung binh tac dung len dat nen:
64kN/ml
He sd tap trung Ung suat n =2.56.
Tien hanh phan tich Id trinh Ung suat cua dat nen tai mui cpc va diem glUa hai cpc be tdng cdt thep, Id trinh Ung suat cua dat dudi mui cpc da't xi mang. Theo ket q u i phan tich d cac Hinh 7, 8, 9 thi dudng Ung suat cdn nSm dudi dudng trang thai tdi han CSL, vi vay cdng trinh dat dp dn dinh theo trang thai tdi han.
5.3. Phan bo Ung sudt trong khoi gia co coc ddt ximang
Ket qua tinh toan kha nang chju tSI cho phep cua cpc dat xi mang cd ham lupng 200kg/
m', (t)=1m, L=15m trong dat set yeu la q „ j = 609 kN/m^ (FS=3).
Lfng suat tac dung len cpc dat xi mang va dat nen phu thudc rat nhieu vao chieu cao va vat lieu khdi dap, mddun bien dang cua cpc va dat nen xung quanh cpc. £)ieu nay dUpc the hien thdng qua he sd giam Ung suat SRR trong dat nen. Ket qua tinh toan dUpc trinh bay trong Bang 2.
5.4. He so on dinh dUac phan tich bdng phuang phdp phan tcfhCfu hgn
Ket qua phan tich dn djnh tong the cdng trinh theo cac qua trinh thi cdng va lau dai dupc the hien trong Bang 3.
6. Ket luan
Khi sU dung giai phap khdi dat gia cd xi mang lam tudng chan thi chuyen vi ngang cua nen dat ndi chung va cua he cpc be tdng cdt thep ndi rieng giam rat Idn. Theo ket q u i nghien cUu tinh toan cho cdng trinh cau tau khu vUc Cang Giao Long-Ben Tre thi chuyen vi ngang giam hon 50%. Khdi gia cd dat xi mang dang tUdng chan cd ham lupng 200kg/m^ se dat cudng dp q^= 709kN/m^ la phu hpp cho loai dat bun set trang thai chay.
Nen dat ben trong nen dUdng bai hang khi dupc gia cd bang cpc dat xi mang cd tac dung han che dp lun lech giUa nen dudng va cau tau rat Idn. Sau thdi gian cd ket lau dai, vdi giai phap gia cd sau cpc dat xi mang cho Idp dat bijn set cd be day 15m, dp lun lech cd gia tri la 16cm (it hdn mdt giai phap gia cd da dUpc tinh toan khae nhU la dem cat gan 4 lan).
05.2011 ^ E i n i i l B l 5 5
Bang 1: Ket qua thi nghiem nen nd hong
TT 01 02 03
Ham lUPng t h i nghiem 200kg/m^(13%) 220kg/m^(14%) 250kg/m^(16%)
Dung trpng khdyk (kN/m^)
12.5 12 12.4
Dung trpng Udtyw (kN/m')
17.4 17.2 17.4
e d am W (%) 38.8 43.5 39.8 TT
01 02 03
Ham lupng t h i nghiem 200kg/m3(13%) 220kg/m^(14%) 250kg/m'(16%)
SUc khang nen nd hdng q^
(kN/m^) 1412 1527 2084
Mddun dan hdi Eo (kN/m^)
89240 90036 92650
Khi sU dung giai phap cpc dat xi mang de cai tao nen dat yeu vdi vai dia ky thuat phu ben tren dau cpc, Ung suat do tai trpng ben tren phan Idn se dupc truyen cho cpc dat xi mang thdng qua hieu Ung vdm. SU phan bo Ung suat phu thupc vao khoang each giUa cac cpc, chieu cao cua nen d i p va tinh chat cua vat lieu dap, mdi quan he giUa dp cUng cua cpc va cua dat nen.Vdi chieu cao dap khdng Idn thi phupng phap Terzaghi cho ket qua phu hpp vdi phupng phap phan tU hUu han, he sd tap
trung Ung suat n co gia tri tU2-;-3. •
Bang 2: Ket qua phan tich sU phan bd Ung suat trong khdi gia cd cpc dat xi mang TT
01 02 03 04
Phuong phap tinh
Terzaghi Hewlett& Randolph
Guido Swedish
SRR
0.89 0.57 0.47 0.15
n
2.42 9.67 13.96 67.55
Lfng suat len dat xung quanh cpcos
(kN/m^) 55kN/m^
35kN/m^
29kN/m^
9kN/m^
Lfng suat len dau cpc da'txi mang etc
(kN/m^) 133kN/m"
341kN/m' 407kN/m"
608kN/m^
Bang 3: He sd dn dinh tdng the phan tich bang phuong phap Phan tU hUu han Budc tinh toan
BUdcl Budc 2 Budc 3 BUdc 4 Budc 5 Budc 6
Ndi dung Thi cdng cpc dat xi mang
Nao vet Idng sdng Thi cdng ben cau tau
Thi cdng nen dUdng Khai thac sUdung
Cd ket lau dai
He s o o n dinh FS 13.13
6.74 5.85 4.75 3.45 4.02
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Hinh 5: Co liin lech giQa cau tau va nen dUdng theo thdi Hinh 6: Co liin lech giffa cau tau va nen M n g theo thdi gian khi gia co nen bang cpc dat xi mang, AU^^^=160mm gian khi gia co nen bang dem cat, AU^^=600mm
250
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Hinh 7: Lp trinh ifng suat cua dat nen tai mui cpc be tong cot thep
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Hinh 8: Lp trinh u'ng suat cua dat nen tai vi tri giii'a hai cpc be tong cot thep
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Hinh 9: Lp trinh ijfng suat cua dat diroi mui cpc dat ximang
TAI UEU T H A M KHAO
1. Chau Ngpc An - Ca hoc dat - NXB Cai Hgc Quoc Gia Tp. Ho Chi Minh, 2004.
2. D.TBergado, L.R.Anderson, N.Miura, A.S.Balasubramaniam, Soft Ground Improvement Manufaaured in the United States of America.
3. Tieu chuan nganh 22 TCN 207-92, Cong trinh ben cang bien, Tieu chuan thiet ke', Bp giao thong van tai, 1992.
4. Tran Xuan Thp,TranThanh Trung. Tinh toan on dinh cong trinh ben cau tau tren flat yeu. Tap chi fiia Ky Thuat, 2009.
