Xac djnh chuyen vj ngang cua tu'ang vay trong ho dao sau
Ngay nhan bai: 4/12/2013 Ngay sCra bai: 12/12/2013 Ngay chap nhan dang: 25/12/2013
Tran Xuan Tho, Doan Van Toan
T 6 M TAT:
Noi dung cua bai bao la phan tich chuyfa vi ngang cua tvldng vay trong ho dao sau sti dung philong phap phan ttl hiiu han va dam tren nen dan hoi. Ket qua phan tich chuyen vi ngang cua tiidng diigc kiem chiJng vdi so lieu quan trac hien trildng de danh gia 6n dinh cua ho dao. Ket qua chuyen vi ngang ciia tiidng phan tich bang phan tii hfiu han gan sat vdi sd lieu quan trac hien trildng vdi dp sai so khoang 8%. Tuy nhien, chuyen vi nhan dtlgc tfl philong phap dSm tren nen dan hpi cho ket qua ldn hdn ban so vdi phan thil hflu han khoang til 1,88 - 2,47 lan.
ABSTRACT
This paper is aimed at analysing the horizontal displacement of diaphragm vfall in a deep excavation, using the Finite Element method (FEM) and beam on elastic foundation method (BEF).
The analysed results are compared to the measurements to evaluate the stability of deep excavation. The results of horizontal displacement of the diaphragm wall from FEM are equivalent to the monitoring data with the difference of 8%. However, the horizontal displacement results from BEF analysis are higher from 1.88 to 2.47 times than that of FEM results.
Keywords: Deep excavation, diaphgram wall, displacement, Finite Element method (FEM), beam on elastic foundation method (BEF).
PGS.TS. Iran Xuan Tho
Khoa Ky Thuat Xay Diing, Trilclng Dai hpc Bach khoa TP. HCM 268 Ly Thiidng Kiet, Q. 10, TP. HCM
Email: [email protected] DT: 0939.369.777 KS. DoAn Van Toan
Khoa Ky Thuat Xay DUng, Tnidng Dai hoc Kien triic TP. HCM 196 Pasteur, Q.3, TR HCM
Email: doanvantoanraihcmuarc.edu.vn DT: 0973.392.357
I . D a t v a n d e
Dfldi didu kidn dao dat thdng thfldng, mdt Iflpng dat ben trpng hd d i o dflpc d d bd, tap ra i p Iflc dat khdng e i n bang t i c dung ldn tfldng. Ap Iflc dat khdng can bang se l i m p h i t sinh b i l n dang cfla tfldng va be mat dat. N l n dat, d i l u kidn mflc nudc n g i m , hinh dang hd d i o , qui trinh thi edng, phuong phap thi cdng, loai tfldng c h i n gifl va n h i l u yeu t d khae lien quan tdi chuyen vj cua tudng. O l dam b i o dn djnh cfla hd d i o , c i n x i c djnh chuyen vj cfla tudng trong cie giai doan thi cong dao dat.
Hidn nay cd nhieu phuong p h i p d l p h i n tieh tudng vay trong hd dao s i u . Hai phuong phap phan t f l hflu han (FEM) va dam trdn n l n dan hdi (BEF) thfldng dflpc sfldung. FEIVl l i mdt phflong p h i p tflong thieh Si md phdng dng suit - b i l n dang eua dat. Khi lUa chpn g i i i p h i p ddn g i i n hon thi BEF trd t h i n h mdt md hinh dugc sfl dung. O l danh g i i k i t q u i p h i n tich d f l d o i n chuyin vj ngang eua tudng v i y thi can t h i l t p h i i t i l n hanh quan t r i e chuyen vj ngang eua tudng khi tien h i n h thi edng hd d i o . Tudng v i y trong hd d i o siu edng trinh Hud Tower, H i Ndi dupe nghidn cflu trpng b i i bap niy.
2. Phuong phap nghien cflu
Phflong phap phan t f l hflu han thdng qua phan m i m Plaxis dupe sfl dung d l phan tich. DUa v i p dae diem dja tang va eac d i e trUng co ly eua c i c Idp dat, md hinh Mphr - Cpulomb (MC) dugc ap dung trong mo phdng tinh toan.
Phuong phap dam tren n l n d i n hdi thdng qua chuang trinh VEX dugc sfl dung md phdng p h i n tich dua tren g i i tri he sd nen theo phuong ngang eua nen dat. Xac djnh he sd nen theo phuang ngang dua trdn phuong trinh cfla Ou (1997).
Oe cac cdng cu p h i n tieh nay dupe sfl dung an t p i n thi can dflgc kiem chflng b i n g cich ddi chieu vdi ket q u i quan t r i e hidn trfldng. Tien h i n h quan t r i e chuyin vj ngang eho tudng v i y hd dao trong q u i trinh thi edng dao dat bang cic t h i l t bj Inclinometer (Hinh 2).
3. Mo t i cong trinh va mo phdng tinh toan 3.1 Mo ti eong trinh
Cdng trinh HudTower cd 3 t i n g ham, sfldung phflong phap thi cdng Top-Down vdi 4 giai doan d i o dat. Hd dap rpng 40m v i s i u n h i t 12,0m.
Hd dap dupc chan gid b i n g tudng v i y ed b l day 800mm vdi dp s i u eua tudng 25m, thanh giang H300x300x10x15 vdi k h o i n g c i c h thanh giang l i 5,0m v i k i t hgp vdi san tang ham l i m giang chdng cho thi edng dao dat. Sau khi thi edng xong tfldng v i y DW800 va epe khpan nhdi va kingpost thi t i l n h i n h thi edng dao dat tang ham. Mat cat ngang hd dao dflgc md t i trong Hinh 1.
3.2 Bgc diem dia chdt eong trinh
Ciu tao dja c h i t va chi t i l u eo ly cfla eac Idp d i t :
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SET CLING r,.i = 20.4kN;m' f' =17°13' C =42.5kN;m' S u = i a o k N ; m ' N = 30 - 40
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CAT PHA, TRANG THAl CHAT rs,i = 2 0 . 1 k N ; m '
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Hinh 3. Mo hinh phan tich ho dao trong VEX
- Ldp 1: Set pha, mau xam trang, trang t h i i ddo mem den ddo cflng, d i y 12m, trgng Iflgng r i l n g trdn mflc nudc ngam y^^^^^ = ^6,5kN/m^
trgng Iflgng ridng b i o hda y^^^ = 19,8kN/m3, c'
= 19,5 kN/m^ cp'= 17°13', sfle ehdng c i t khdng t h p i t nfldc S„ = 50 kN/m^ he sd tham k = 8.64E"' m/ngay-dem, module bien dang t i l p tuyen E^^,
= 2800N (SPT)= 25000 kN/m^ he sd Poisson'v
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h i # » t i t * ""» .^. « V - i. it i'. '<• •• >i .1 < li" ji t Hinh 4. Mo hinh phan tich ho dao trong Plaxis
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Hinh 5. Ket qu3 chuyen vj ngang cOa tilJng trong cac giai doan dao dat (bang VEX)
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Hinh 6. Ket qua chuyen vj ngang ciia tudng trong cac giai doan dao dat (bang Plaxis)
= 0,35.
- Ldp 2: Set mau nau vang, trang t h i i cflng, day 18m, y^^ = 20,1 kN/m=, c' = 42,3 kN/m^ cp' = 21 »26', sdc chong eat khdng t h o i t nudc S^ = 180 kN/m^ k = 8.64E-^ m/ngay-dim, E , = 2800N (SPT) = 89600 kN/m^ v = 0,35.
- Ldp 3: Ldp eat pha, mau nau v i n g , trang t h i i c h i t , b l day rat Idn, y^^^ = 20kN/m^ e' = 0 mim\ cp' = 29°19; k = 0,864m/ngiy-dem, E,^, - 2500N (SPT) = 80000 kN/m^ v = 0,3.
3.3 Bic diem tudng vdy BW800 Tudng v i y cd c h i l u s i u t f l mat dat t i i nhidn L=25m, tudng day 800mm. Bd tdng dirng mac M350(B25) ed modul dan hdi E, = 3,0x10'kN/
m^ dp cdng ehdng nen EA = 2,4x10' kN/m, dp cflng ehdng udn El = 1,28x10' kN/mVm, He sd Poisson v = 0,2.
3.4 Bic diem sin tret vi hdm B1, B2 San tret, ham 1 (Bl) va s i n ham 2 (82) cd
eao dp l i n lucrt la ±0,0; -3,5m va -7,0m san day 200mm, be tdng m i c M350 (B25) co modul d i n hdl la E„ = 3,0xl0'kN, dp cflng dpc true EA = 6,0x106 kN.
3.5Biediemthanheh6ngH300x300x10x15 He thanh chdng thep hinh H300x300x10x1521 tai cao dp -2,0m, sfl dung thep ed mac SS400 hay (CT34) cd modul d i n hdi E = 2.1xl0'kN/m^ dp cflng dpc true EA = 4,914x10' kN, budc chdng L^ = 5,0m.
3.6 Quan trie Men truing
Quan t r i e c h u y i n vj ngang eua tfldng v i y theo tflng giai doan d i o dat va thi cdng t i n g ham. Trflde khi do be tdng tfldng, c i e thiet bj Inclinometer dflgc d i t trong eac dng thep de do chuyen vj ngang cfla tudng theo chu vi tfldng vay nhfl Hinh 2.
Dfla trdn nguyen t i e con l i e trgng lugng ludn ludn duy tri tinh chat thang dflng eua diy dgi, thdng qua viec do lay gdc kep gifla dfldng true d trong m i y vdi dudng t h i n g dflng cfla day dgi eon lac de tinh ra chuyen vj ngang cfla doi tflgng p h i i do. 6 d i u tren con l i e ed djnh mpt la ddng nhip, la ddng nhi'p dau tren ed djnh, dau dfldi dfla v i o d i y lac, khi may do nghieng bj n g h i i n g , day lac dfldi t i c ddng cfla trgng lfle con lie duy tri t h i n g dflng nen ep vao l i ddng lam chp la ddng bj eong, nhd vao p h i l n bien dang didn t r d d i n trdn l i ddng dfla ra tin hieu didn, may t h u trdn mat dat se t h u n h i n tin hieu didn t r d v i tinh ra trj udn cong cfla la ddng, tfle la cd the b i l t dflgc gdc nghieng 6 cua m i y do n g h i i n g , t f l do tinh dflge chuyen vj cua doi tflgng p h i i do.
3.7 Mo phdng tinh todn
Q u i trinh thi cdng hd d i o s i u dflge mo phdng bao gdm c i c giai doan sau:
Giai doan 1 :Thi cdng tudng vay day 800mm, sau 25m.
Giai doan 2: O i o dat lan 1 xudng cao dd -3,0m.
Giai doan 3: Lap giang chdng H300x300x10x15 tai eao dp -2,0m.
Giai doan 4: Oao dat lan 2 xudng cao do -5,0m.
Giai doan 5: Thi cdng s i n h i m Bl tai cao do -3,5m.
Giai doan 6: T h i o chdng H300x300x10x15 va thi cdng s i n tret day 200mm.
Giai doan 7: Oao dat lan 3 xudng cao do -9,0m.
Giai dpan 8: Thi cdng s i n ham B2 tai cap dd -7,0m.
Giai dpan 9: Gap dat l i n 4 xuong eao do -12,0m, rdi thi edng eae d i i mdng be.
Hinh 3 Md hinh phan tich hd d i o bang chuong trinh VEX va md hinh p h i n tieh ho dao trong Plaxis dflgc md ta trong Hinh 4.
4. Ket q u i p h i n tich
trmh VEX)
K i t q u i p h i n tich c h u y i n vj ngang eua
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tudng qua eac giai doan dao dat bang phuong p h i p dam tren nen dan hdi dugc md t i trong Hinh 5. 6 giai doan dao dat l i n 1, tfldng cd xu hfldng djch chuyen vao bdn trong hd dao, chuyin vj ngang Idn n h i t d dinh tfldng u_^^^ = 20,76mm. Giai doan dao dat lan 2, chuyen vj efla dinh tfldng g i i m vi d i khi lap thanh chdng, ehuyin vj ngang Idn n h i t cfla tfldng la u^^^ = 24,3mm d vj tri dp s i u 6,0m sp vdi mat dat tU nhien. Giai dpan dao d i t lan 4, tudng chuyen vj vao bdn trong hd dap nhieu n h i t va cd xu hfldng bj udn bung, ehuyin vj ngang eua dinh tfldng la 19,8mm, chuyen vj Idn n h i t la u^^^=
41,17mm d vj tri dp s i u 10m sp vdi mat dat t f l nhien.
4.2 Kit qui phdn tieh bing FEM (chuang trinh Plaxis)
Ket q u i p h i n tieh chuyen vj ngang eua tudng qua cae giai dpan d i p dat bang phfldng p h i p phan t f l hflu han dflgc md t i trong Hinh 6.
d g i a i doan dao dat lan 1, chuyen vj ngang Idn nhat d dinh tfldng u^^^ = 11,04mm. Giai doan dao d i t l i n 2, c h u y i n vj cfla dinh tfldng g i i m vl d i khi lap thanh ehdng, chuyen vj ngang Idn nhat efla tudng l i u^^^ = 13,54 mm d vj tri dp s i u 6 m so vdi mat d i t t f l nhidn. Giai dpan d i o d i t l i n 4, chuyin vj ngang cua dinh tudng l i 12,34 mm, chuyen vj Idn n h i t l i u^^^ = 18,5 mm d vj tri dp siu 10 m so vdi mat dat t u nhien.
4.3 Ket q u i quan t r i e
K i t q u i quan trac ehuyin vj ngang efla tudng tai vj tri dng 1-2 dupe md t i trong Hinh 7.
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Hinh 7. Ket qua quan trac chuyen vj ngang ciia tirdng trong cac giai doan dao dat
4.4 Bdnh gid ket qua phdn tich vdi ket qud quan trie hien truing
Hinh 8 tdng hgp k i t q u i c h u y i n vj ngang cua tfldng trong c i c giai doan thi cdng dao dat theo Plaxis, VEX v i k i t q u i quan t r i e hien tudng. Trj sd b i l n dang tinh t o i n eua tfldng vay tinh toan bang Plaxis g i n sat vdi sd lieu quan trie thflc te vdi dp sal k h i c k h o i n g 8% v l dp Idn. Tuy nhien, cung dua tren k i t q u i sp sanh nay, chp thay c h u y i n vj n h i n Siigc t f l VEX eho k i t q u i Idn hon ban so vdi Plaxis k h o i n g t f l 1,88 + 2,47 lan.
Trong sudt qua trinh dao dat, tudng v i y sd p h i t sinh hai xu hfldng ehuyin vj, tdng hai xu hfldng nay se tao ra djch chuyen ngang Idn nhat cho ti'-^ J B d la xu huong djch chuyen ngang
H
— \ H
Hinh 8a. Bao dot tan 1 den -3,0m
Chuyen v | a g i n g (m)
Hinh 8b. Dao dot Ion 2 6en -5, Om
Cbin*cD v | ngiDg (m)
Hmh ic Bao dot lan 3 den -9,0m Hinli Sd Boo dot Idn 4 dm -U,Om Hinh 8. Chuyen vj ngang ciia tucing bang quan trac va tinh toan bang Plaxis, VEX
v i o trong hd dao cfla t o i n tudng (xu hfldng 1) va xu hflong u o n p h a n b u n g cfla tfldng (xu hfldng 2). Trong giai doan d i o d i t ban d i u , xu hfldng 1 l i chu dao, tuy n h i i n trong cic giai doan sau (khi da bd tri hd ehdng va khi thi edng eic san tret, s i n ham 1, s i n ham 2) thi xu hudng 2 dugc t h i hidn r i t rd va c h i l m Uu t h i .
Vj tri tfldng dat gia trj cue dai (tai vj tri tfldng bj uon bung n h i l u nhat) cd xu hfldng djch ehuyin theo c h i l u s i u d i o dat t f l vj tri k h o i n g 8m d (giai doan dao d i t l i n 3) t i n g len vj tri 10m so vdi dinh tfldng (trong giai doan dao dat l i n 4). Ben canh do ehuyin vj ngang eua tudng cung t i n g dan theo c i e giai doan dao dat.
Theo tieu chuan thiet ke ASTM, c h u y i n vj ngang cua tudng eho phep k h o i n g [ux] =1,5 inches = 3,81 em, do dd ehuyin vj ngang cfla cflc dai thflc te eua tfldng v i y la umax =l,8em, ndn tfldng vay hd dao van d i m b i o d i l u kien dn djnh.
5. Ket l u i n
K i t q u i c h u y i n vj ngang eua tudng tinh t o i n b i n g Plaxis g i n s i t vdi sd lieu quan t r i e hien trfldng vdi do sai sd k h o i n g 8%.Tuy n h i i n , chuyen vj nhan dflgc t f l chflong trinh VEX cho k i t q u i Idn hon han so vdi chuong trinh Plaxis k h o i n g t f l 1,88-2,47 l i n .
Du rang phflong trinh efla Ou cho ra ket q u i khdng phu hgp vdi ket q u i quan t r i e trong d u
i n , tuy nhidn cic thdng sd cfla Idp d i t set l i cic ydu t d i n h hudng tdi phuong trinh. He sd nen theo phuang ngang cd khuynh hfldng tang theo he so Poisson, modul d i n hdi cfla d i t v i sfl t i n g ldn cfldng do dat n l n . Trong sfl tuong p h i n , he sd nen theo phuong ngang g i i m xudng vdi sfl t i n g len be rdng hd dao v i t i n g len c h i l u d i l c i m s i u cua tfldng.
O l dflpc hgp ly trpng viec thflc hidn tinh t p i n i p lfle ngang doe theo chieu s i u vung dat bi p h i hoai keo gdm c i b i l n dang cfla tfldng va phu hpp vdi hd d i o thflc, sfl h i l u ehinh i p Iflc ngang phia sau lung tudng bang hai l i n c h i l u s i u m i vung dat bj p h i hoai keo la dupe xac djnh rd trong phflong phap dam tren nen d i n hdl.
TAI LlCU THAM KHAO
[1] Ou, Chang-Vu (2006), Deep Excavation theory and practice. First edition, Taylor and Francis/Balkema, Netherlands.
[2] Malcolm Puller (1996), Deep Excavation a practical manual, first edition, Thomas Telford, New York.
[3] Monitoring of Diaphragm Vtfall Displacement and Assodated Ground Movement, Braced Excavation Adjacent to Historical Building at The Bank of Chao Phraya River. Bangkok, Thailand, 2000.
[4] Vesic, A.B. (1961), Beams on Elastic Subgrade and the Winklers's Hypothesis, Proceedings, Fifth Intemational Conference on Soil Mechanics and Foundation Engineering, Paris.
