0 0 00 0 KHI XAY

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KHOA HOC - CONG NGHE Tap Chl GTVT 11/2009 1

PHAN TICH LUN BE MAT SINH RA KHI XAY Dl/NG HAI HAM GAN NHAU

TS. BULDUfC CHINH KS. N G U Y I N THAI KHANH Vien Khoa hgc va Cdng nghe GTVT

1. Md dau

Thdi gian qua, cd nhi'eu du an cbng trinh ng'am da dupc xay dUng d cac db thj Idn tren the gidi. Do mbi trudng db thi rat chat hep, lai cd nhi'eu chudng ngai vat dudi Idng da't cho nen viec xay dUng cac h'am g'an nhau la kha phb bie'n. Ngoai ra, trong nhieu trUdng hdp cac h'am mdi cung dUpc xay dpng ben canh cac h'am hien cd. Viec xay dpng cac h'am g'an nhau cd the gay ra dp lun kha Idn tren mat da't dan den cac hU hdng cho cac cdng trinh xung quanh. Viec dU bao lUn be mat sinh ra do hai h'am dat g'an nhau khd khan hdn nhi'eu so vdi dp lun sinh ra khi xay dpng h'am dPn.

Xac djnh dUdc dUdng cong lUn b'e mat sinh ra do xay dung h'am dbi cb the danh gia dupc pham vi anh hudng va han che cac hU hdng cho cac cbng trinh xung quanh. Do vay, da cb mbt sb nghien cUu lien quan den van de nay dpa vao cac phuong phap thpc nghiem nhu Peck (1969), Cording va Hansmire (1975), Shirlaw (1985). Trong qua trinh thpc hien cac dp an, mpt sb tac gia cung da thpc hien cac quan trac lun sinh ra tren h'am dbi, trong dd dien hinh la nghien cUu kha toan dien cua Suchatvee Sunwansavat (2006) d dp an xay dUng tuyen Metro TP. Bangkok, Thai Lan. Td viec phan tfch cac ke't qua do dac nay, bng da d'e xua't cac phUdng phap md ta dUdng cong lun tren h'am ddi la phuong phap cbng tac dung va phUOng phap sU dung he thbng Ndron nhan tao (Artificial Neural Networks-ANN).

Trong cac dp an Metro d cac db thj d Viet Nam nhu Ha Nbi va TP. Hb Chf Minh, cac tU van cung da dUa ra cac phUdng an trong db cd nhi'eu doan xay dUng cac h'am g'an nhau. Viec nghien cUu phan tich dp lun sinh ra tren h'am ddi la c'an thie't de xac djnh khoang each bb trf cac h'am hpp ly trong di'eu kien chat hep cua cac db thj d nudc ta. Trong bai bao nay trinh bay mbt sb ke't qua tfnh toan lun sinh ra tren h'am ddi bang cac cPng thUc thpc nghiem va phUdng phap sb sd dung ph'an m'em Plaxis 2D cho vj trf tren tuyen Metro Ben Thanh - Sudi Tien d TP. Ho Chf Minh.

2. Dddng cong lun be mat sinh ra do xay ddng ham

TU ke't qua quan sat d mdt sb dp an xay dpng h'am mbt sb tac gia da cho rang dUdng cong lun sinh ra tren h'am dbi cb hinh dang thay dbi. Khac vdi dUdng cong lun tren h'am dOn cd dang dbi xdng nhu tren hinh l a , dudng cong lun tren h'am dbi cd the cd dang dbi xdng qua diem gida hai h'am hoac lech sang mbt ben nhU hinh l b . Tuy nhien, dUdng cong lun nay cung cd the cd hinh dang khbng dbi xdng nhu tren hinh Ic.

Dbi vdi h'am dOn, Peck (1969) da quan sat thay dudng cong lun b'e mat cb the dUdc bieu dien bang dudng cong Gauss. Cac dac trung cua hamsb va cac mbi lien he gida cac kfch thudc dUpc bieu didn nhu tren hinh 2.

0

a. DUdng cong lun ddi xUng phia tren ham dan

b. Duang eong lun ddi xUng phia tren ham doi

00

c. Duang cong lun khong doi xUng phia tren ham doi

0 0

Hinh 1. Cac hinh dang dudng cong lun be mat Tpa dp Idn nha't cua dudng cong Gauss chfnh la dp lun Idn nhat, S^^^do dd dp lun Sd tai mdt diem bat ky cd the xac dinh:

/ S =S^^.^exp

111

2i'- -> \

(1) Vdi y la khoang each tU tim h'am de'n diem xac djnh db lun.

Diem udn

Do lun

Hinh 2. DUdng cong Gauss mo ta lun tren ham ddn Dua vao cac quan sat d h'am ng'am Chicago, Peck cung gpi y rang dudng cong lun phia tren h'am dbi cd dang khdng dbi xdng. Ong chl ra rang di'eu nay la do sU mat da't (ground loss) khi xay dpng h'am thU hai Idn hdn so vdi khi xay dpng h'am thd nhat. Tuy nhien cung trong bao cao dd bng cung da cd nhan xet rang trong trudng hpp hai h'am dupc dat g'an nhau d mdt mdc dp nha't djnh, thi dudng cong lun phfa tren cd dang dbi xdng gibng nhu dbi vdi h'am don. Do dd cd the sd dung ham

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KHOA H O C - C O N G NGHE

Gauss nhu d cbng thdc (1) de md ta dudng cong lun tren h'am dbi.

3. Phan ti'ch ti'nh toan lun be mat phfa tren ham doi

3.1. Tom tat cac phuong phap tinh lun ddi vdi ham ddn

De phan tich tfnh toan lUn b'e mat tren h'am dbi, c'an phai nam rd cac phUdng phap xac djnh lun b'e mat phfa tren h'am ddn. Trong ph'an nay gidi thieu tdm tat cac phUdng phap da dUdc thda nhan rdng rai trong thpc te.

a. Cac phuang phap thuc nghiem

Nhu da trinh bay d tren, dpa vao cac quan sat thuc nghiem Peck da dUa ra dUdng cong Gauss de mb ta lun sinh ra tren h'am ddn. Cho den nay, day la gia thie't dupc thUa nhan rbng rai nhat trong thpc te. Cac tac gia di sau h'au he't deu sd dung ham Gauss nhung cb dUa ra dupc cac cbng thdc khac nhau de xac djnh cac thbng sb dac trung la S^ax va /. Mair (1993) dUa ra cdng thdc tfnh S^ax rihU sau:

V.

2pi : 1 . 2 5 2 ^ (2) Trong db /la khoang each td tim h'am de'n diem ud'n cua dudng cong cdn gpi la thbng sb b'e rbng dudng cong lun; S^^^ la dp lun Idn nha't; V^ la dp mat mat the tich (mat dat); Vi^ la ty le ph'an tram mat mat the tich; R la ban kfnh cua h'am.

b. Phuang phap eua Verruijt va Booker (1996) Verruijt va Booker (1996) da phan tfch lun tren h'am don trong mbt ban khbng gian dan hbi dang hPdng.

Bien dang cua h'am bao gbm bie'n dang theo phUPng ban kfnh va bien dang hinh ovan. Theo phUdng phap nay, dp lun b'e mat dUpc xac dinh nhu sau:

S =4{\-n)e — ^H + H'

Trong dd s la bien dang nen vd h'am theo phUdng ban kfnh; 5 bien dang vb h'am theo hinh ovan; H la dp sau dat h'am. Hinh dang cua dUdng cong lun phu thudc vao he sb Possion u.

c. Phuang phap cua Loganathan va Poulos (1998) Loganathan va Poulos (1998) da phan ti'ch lun tren h'am ddn cb xet de'n khoang hd gida da't va vd h'am trong phuong phap khien dao. Theo phuong phap nay, dp lun b'e mat dupc xac dinh nhu sau:

S =4i\-n)R-e- H

y + H-exp 1.38y'

"(H+Rf

⁽⁴⁾

3.2. Phuong phap cgng tac dung khdng xet den su tuong tac

PhUPng phap cdng tac dung cung cd the dupc sd dung de xac dinh lun tren h'am dbi ke't hpp vdi cac cdng thUc cua cac phUdng phap da trinh bay d tren. Vi du nhu tren hinh 3, dbi vdi gia thie't phan bb Gauss, phuong phap cbng tac dung cd the cho ke't qua dp lUn cua b'e mat da't bang:

S =S _.KAeJ^P [y+DIl]

2; + S„ ^exp

{y-Dlif

2il

⁽⁵⁾

Vdi /^, /gia thdng sb b'e rbng dudng cong lun tai diem h'am thU nhat va thU hai. S^g = 0 dbi vdi trudng

hop khbng cd tuong tac. Neu hai h'am cb dUdng kfnh va mat mat dat gibng nhau, thl S^^axA = Sma>^B va M = 'B- Cubi cung ta se cb dp lun tren be mat dat bang

S = S

P IT exp (•V + P / 2 ) ' 2/- -exp

[y^Diil

2r (6) 3.3. Tinh lun tren ham doi co xet den sU tuang tac giQa hai ham

Trong trudng hpp cac h'am song song dUdc xay dung g'an nhau thi khbng the bo qua tUdng tac giOa chUng. Sagaseta va nnk (1999) da nghien cdu su tUdng tac gida hai h'am song song sd dung ph'an m'em FLAC. Hp da dUa ra he sb phan anh sp tUdng tac giQa hai h'am dbi nhu sau:

n =

V -V

^s "so (7)

Trong dd VQ la the tich lun sinh ra do h'am thU hai;

VQO la gia trj cua VQ ne'u khdng cd h'am thd nhat. Cac anh hudng tuong tac la dang ke khdng chi vdi cac h'am dao theo phUdng phap thdng thudng ma cdn ca dd'i vdi h'am thi cbng bang may dao h'am can bang ap lUc da't EPB TBM. Nhin chung, de xet den sp tUdng tac giOa hai h'am c'an sd dung de'n phUdng phap sb vdi sU trd giUp cua cac ph'an m'em dja ky thuat chuyen dung.

3.4. Cac ket qua tinh toan liin tren ham doi Trong ph'an nay tac gia da sd dung phUdng phap cdng tac dung ket hdp vdi cac cbng thdc tfnh da trinh bay d tren. Ph'an m'em Plaxis 2D dUdc sd dung de so sanh dbi chieu va xet den sp tUPng tac gida hai h'am.

Vf du dupc ap dung tfnh toan d day la mdt doan trong dp an metro Ben Thanh - Subi Tien vdi dieu kien dja chat nhu bang 1. DUdng kfnh h'am bang 6.0m; chi'eu day vd h'am bang 0.6m. Xet cho cac trUdng hpp hai h'am dat each nhau fan lupt la 1.5, 2, 2.5, 3 va 3.5 fan dPdng kfnh h'am.

Lap 1

Lop 2 a:

Ldp 3 f ?? A m- W D ^

* .

'

Lcrp4

Lop 5

Hinh 3. Ky hieu cac kich thudc cd ban Da tien hanh ti'nh lun theo phUPng phap PTHH, phuong phap cua Mair, phuOng phap cua Verruijt va Booker (V&B) va phuong phap cua Loganathan va Poulos (L&P) vdi cac trudng hpp dp sau dat h'am va khoang gida cac h'am thay dbi. Tren hinh 5 bieu diin dp lun tinh toan trong trudng hpp D = I 2 m va H = 15m.

Cac ke't qua cho thay trong trudng hpp hai h'am g'an nhau, sU tUPng tac cd anh hUdng de'n dp lun tbng cpng.

Ket qua tfnh toan bang phUdng phap PTHH cho ket qua db lun nhb hdn. Tuy nhien trong Ccc trudng hdp ket qua tfnh theo PTHH, phUdng phap c a Mair va ciiia Loganathan va Poulos la tUPng dbi khdf: .,j Phpong phap ti'nh cua Verruijt va Booker cho ket c, j a dp lun Idn hdn rat nhi'eu.

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KHuA H u C - UUNG NGHE Tap Chl GTVT 11/2009

Bang 1. Cac tfnh chat cua cac lop dat Thong so

Mb hinh vat lieu Dang dng xd Trpng lUpng khb Trpng IUdng Udt He sb tham (ngang) He sb tham (dpc) Mb dun dan hbi He sb Poisson Lpc dfnh Gbc ma sat Chieu day Idp

Ldp 1 Set mem MC

Thoat nUdc 1

18 1.8e-5 1.8e-5 1000 0.33 8.5 5 8

Ldp 2 Set dec MC

Thoat nUdc 20

21 4.7e-5 4.7e-5 2000 0.33 2.48 17 5

Ldp 3 Cat rdi MC

Thoat nPdc 20.8

21 0.5 0.5 30000 0.3 1.1 28 26

Ldp 4 Set cifng MC

Thoat nUdc 20.4 22

1.36e-5 1.36e-5 10000 0.33 3.8 16 13

Ldp 5 Cat chat MC

Thoat nUdc 19.6

20.5 0.5 0.5 120000 0.3 1.5 21 -

Don vj - - kN/m^

kN/m^

m/ngay m/ngay kN/m^

- kN/m^

o

m Bang 2. Cac tfnh chat vat lieu cCia vo ham

Thong sb Mo hinh vat lieu Do cufng doc true Do cung chong uon B'e day tudng dudng Trong lu'dng He sb Poisson

Ten Loai vat lieu EA El d w

u

Gia trj Dan hbi 1.40. 10' 4.20. 10^

0.6 9.0 0.3

DPn vi - kN/m KNmVm m kN/m/m -

Hinh 4a. Mo hinh dau vao cua bai toan trong

phan mem Plaxis 2D

Hinh 4b. Bien dang sau khi thi cong xong ham

thU hai

-36 -32 -28 -M -20 -16 -12 .8 ^ 0 4 8 12 16 20 24 28 32 36 Khoang each (m)

Hinh 5. Ket qua tinh liin theo cdc phuong phap (trudng hgp D = 12m, H = 15m)

4. Anh hPdng cua khoang each giufa hai ham va dp sau dat ham de'n sU tPdng tac

De xet de'n anh hudng cua khoang each tUdng dbi gida hai h'am va dp sau dat h'am de'n dp lun phfa tren hai h'am da tie'n hanh tfnh toan bang PTHH cho cac trudng hpp dp sau dat h'am thay dbi va khoang each tuong dbi gida cac h'am (ty sb gida khoang each va dudng kfnh h'am) thay dbi tU 1.5 den 3.5. TU cac ke't qua tfnh lUn nay da xac djnh he sd tUdng tac r\ theo cdng thdc 7 (d day thay dp mat mat the tich l/bang dp lun ldn nhat S^g^).

5. Anh hudng cua khoang each giQa hai ham va dp sau dat ham den sd ti/dng tac

De xet de'n anh hudng cua khoang each tUdng dbi gida hai h'am va dp sau dat h'am den db lun phfa tren hai h'am da tie'n hanh tinh toan bang PTHH cho cac trudng hdp dp sau dat h'am thay dbi va khoang each tuong dbi giOa cac h'am (ty sb gida khoang each va dudng kfnh h'am) thay dbi tU 1.5 de'n 3.5. TU cac ke't qua tinh lun nay da xac djnh he sb tUdng tac r\ theo cbng thdc 7 (d day thay dp mat mat the tfch l/bang dp lun Idn nhat S^gx)- Tren hinh 6 va hinh 7 bieu d i i n sU lien he gida he sb tUdng tac r| va khoang each tUOng dbi giOa cac h'am va db sau dat h'am. Cac ket qua cho tha'y khoang each tUdng dbi cb anh hudng Idn den sU tUdng tac gida hai h'am. Khi khoang each tUdng dbi nay Idn hdn 3 sU tUdng tac h'au nhu khbng xay ra. Dp sau dat h'am cung cb anh hudng de'n sU tUdng tac, h'am cang dat nbng thi sp tUdng tac gida cac h'am cang Idn.

2

- I -

1.5 2 2.5 3 Khoang each tUdng doi

3.5 Hinh 6. anh hudng cua khoang each tuong dd'i

den su tuong tac giUa hai ham

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KHOA HOC - CONG NGHE

O '•-'

•(6

**

? 1

''O 0 5

(OJ-

X

-0.5

1 ^ = ! ^ ^ ^ -

^^^iv —"....V

—•—H=8m

—•—H=10m

—A—H=15m -*<—H=20m

1.5 2 2.5 Khoang each tUdng doi

3.5

Hinh 7. Anh hudng cua do sau dat ham den su tUdng tac giUa hai ham

6. IVIpt so nhan xet

Bai bao da trinh bay mbt sb phUdng phap phan tfch tfnh toan dUdng cong lun sinh ra d be mat dat phfa tren hai h'am dUdc xay dpng g'an nhau. TU cac phUPng phap nay da tfnh toan cho mbt trubng hdp d dp an metro Ben Thanh - Subi Tien d TP. Hb Chf Minh. TU cac phan tfch tren va cac ke't qua tfnh toan cd the dUa ra mbt sb nhan xet nhu sau:

(1). Viec phan tfch lun sinh ra phfa tren hai h'am xay dung g'an nhau va c'an thiet de xac djnh dUpc khoang each gida cac h'am hpp ly. Viec md ta dUdng cong lUn nay cd nhieu khb khan hdn so vdi trudng hpp h'am ddn do nd phu thupc nhieu yeu tb dac biet la khoang each gida hai h'am.

(2). Cac ket qua tinh toan lun cho thay rang phUPng phap PTHH cb xet den sU tUdng tac cho ket qua dp lun nhd nha't. Ket qua nay cung tuOng dbi phu hpp vdi ket qua tfnh theo phuong phap cua Mair cung nhu phUdng phap cua Loganathan va Poulos. Ke't qua tinh lun theo phuong phap cua Verruijt va Booker cho ke't qua dp lun

Idn hdn rat nhi'eu so vdi cac phUdng phap cdn I '

(3). Dp sau dat h'am va khoang each tU' .-^'9'^^

hai h'am cd anh hudng Idn de'n sU tUdng J^^^ ^ai h'am. Khi khoang each tUPng dbi be ^g 1 -5, SL ^UPng tac nay la rat Idn. Khi khoang each tJong dbi Idn hPn 3 thi sp tUdng tac h'au nhu khbng xay ra. Dp sau dat h'am cang nhb thi anh hudng gida hai h'am cang ldn •

TAI LIEU THAM KHAO

[1]. Bui Dufc Chinh, Nguyin Thai Khanh (2004),

"l^ng dung phuong phap ph'an td hdu han trong tfnh toan ke't ca'u cbng trinh ng'am". Tap chi Cau dUbng Viet A/am, sb 12/2004, tr. 24-28.

[2]. Loganathan N, Poulos HG (1998), "Analytical prediction for tunneling-induced ground movements".

Journal of Geotechnical and Geoenvironment Engineer- ing, ASCE Vol. 124, pp. 846-856.

[3]. Mair RJ, Taylor RN, Bracegirdle A (1993),

"Subsurface settlements profiles above tunnels in clays". Geotechnique, Vol. 43, pp. 315-320.

[4]. Sagaseta C, et al. (1999), "Soil deformation due to the excavation of two parallel caverns". Geot- echnical Enginnehng for Transportation Infrastructures, pp. 2125-2131.

[5]. Suwansawat S (2006), "Superposition Tech- nique for Mapping Surface Settlement Troughs over Twin Tunnels". International Symposium on Under- ground Excavation and Tunnelling, 2-4 February 2006, Bangkok, Thailand, pp. 353-362.

[6]. Suwansawat S (2006), "Using Artificial Neural Networks for Predicting Surface Settlements over Twin Tunnels". International Symposium on Underground Ex- cavation ana Tunnelling, 2-4 February 2006, Bangkok, Thailand, pp. 309-318.

[7]. Verruijt A, Booker JR (1996), "Surface settlements due to deformation of a tunnel in an elastic half plane". Geotechnique, Vol. 46, pp. 753-758.

OANG UYCflf QUAN BO.

(Tiep theo trang 5) nhdng ke't qua dang ghi nhan, nhin chung toan Dang bp tie'n hanh theo dung Ke hoach d'e ra. Ban chi dao Cube van ddng cua Dang bd cd quan Bd, cac Dang bd, chi bd trpc thudc da bam sat sp chl dao cua Ban chi dao Trung Udng, cua Dang uy Khbi va Dang uy cd quan Bb tb chUc trien khai kjp thdi, nghiem tuc cac ndi dung Cudc van ddng va budc d'au cd ket qua thiet thuc.

Da tao dUPc nhdng chuyen bie'n rd net v'e nhan thdc trong can bd, dang vien, cdng chdc, vien chdc trong Dang bd; thdng qua cudc van ddng, y thdc tU giac ren luyen v'e dao ddc, Ibi sbng cua can bb h'au het dUdc nang len, bieu hien qua cac hanh ddng tU giac hang rigay trong cdng viec, mbi quan he vdi gia dinh, tap the va dbng nghiep trong cd quan, ddn vj, tao dUdc ni'em tin trong qu'an chung. Nhung ben canh dd cung cdn cd mdt sb khuyet diem han che, viec trien khai cube van ddng trong toan Dang bd chUa d'eu, hieu qua dat dupc chua ddpe nhu yeu c'au d'e ra. Hoat dbng chi dao, trien khai thpc hien Cudc van dbng trong CNVC, doan vien thanh nien d tb chdc Cdng doan, Doan Thanh nien CP quan Bd cdn chua cu the, thie't thpc.

V'e nhan thdc d mdt sb ft cap uy, can bb, dang vien v'e muc dfch, yeu c'au cua Cube van ddng v i n chua thuc su d'ay du, sau sac, ddng deu. 6 mdt sb dang bb, chi bb viec xay dpng ChUdng trinh hanh ddng cbn chung chung, dan trai, chua sat vdi nhiem vu chfnh trj. Cac hinh thdc tuyen truy'en chua phong phu, da dang.

Nhan djp nay, Dang uy cP quan Bb GTVT da khen thudng 10 tap the va 5 ca nhan cd thanh tfch xua't sac thdc hien cudc van ddng "Hpc tap va lam theo tam gUdng dao ddc Hd Chi Minh" trong 3 nam qua.

Nhan thdc dupe nhdng han che va rut kinh nghiem, de tiep tuc phat huy nhdng ket qua da dat dupc va khac phuc nhdng han che, Dang uy Cd quan Bd d'e ra nhiem vu trpng tam c'an thpc hien het nam 2009 - 2010 va nhdng nam tie'p theo, tao ra nhi'eu mo hinh, dien hinh tien tie'n cua tap the va ca nhan nham day lui sU suy thoai dao ddc, Ibi sbng xay dpng dang bb, chi bp trong sach, vdng manh oan thanh tb't nhiem vp chi'nh tri nam 2009, nghj q

bb, chi bb nhiem ky 2005-2010, hue nam thanh lap Dang, 65 ngay tha nam ngay sinh chu tjch Hb Chf Minf cac cap tien tdi Dai hbi dai bieu toan cua Dang va ky niem 65 nam ngay nganh GTVT •

dai hbi dang i ky niem 80 Nudc, 120 ' d a n g bp thd XI

•'i'l. h d n g

\ H