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cng Lun vn- Nguyn Tng Thanh [email protected]

1. T VN

Trong xu hng pht trin ca t nc, dn c ngy cng tp trung nhiu

v cc khu th nh thnh ph H Ch Minh v H Ni, lm cho nhu cu i li

cng gia tng. iu dn n din tch ng giao thng trn s phng tin

giao thng ngy cng gim. C th, thnh ph H Ch Minh u nm 2009 dn

s thnh ph l 7.123.340 ngi (Bo Thanh nin ngy 13/05/2010). Trn a

bn thnh ph c khong 3600 con ng vi din tch mt ng gn 26 triu

m2, trong cc tuyn ng c b rng nh hn 7m chim n 69,3%, mt

ng giao thng so vi din tch thnh ph ch t khong 1,8 km/km2 . Trong

khi s lng xe thnh ph ang qun l l gn 4.5 triu chic vi khong 400

ngn xe t v 4.1 triu xe m t (Website s GTVT-2009). Do vy, vic phi

tn dng phn khng gian bn di mt t c th l cc tuyn metro l rt cn

thit. Vi mt h thng metro c th thu ht c 25% lu lng xe lu thng

hin nay.

Metro mang li hiu qu kinh t cao nh, c th trnh c vic gia tng chi

ph do n b gii ta khi xy dng ng th cng nh cc cu vt trong

thnh ph. Hn ch c tnh trng kt xe nh hin nay, mi ngy trn mi

tuyn ng u xy ra kt xe vo cc gi cao im v nm 2009 xy ra 74 v

kt xe ko di hn 30 pht trong thnh ph. Ci thin c vn tc lu thng

ca xe c so vi tnh trng hin nay, v nn kt xe thng xun xy ra nn vn

tc xe lu thng trung bnh trong cc gi cao im ch cn khong 10 km/h.

Cc phng php thi cng hm c s dng bao gm 3 phng php

chnh. Mt l, phng php o h l bin php thi cng o t ln, s dng

cc kt cu lm vch m bo t khng b st l xung trong qu trnh thi cng

hm bn di, sau lp t li v tr li mt bng bn trn nh ban u. tuy

nhin, thi cng theo phng php ny yu cu phi c mt bng bn trn trng

tri (c s dng cho tuyn hm Th Thim). Hai l, phng php m c


xy dng trong khu vc vng ni ph hp cho thi cng hm trong ( NATM-

c s dng cho tuyn hm Hi Vn ni thnh ph Hu v thnh ph

Nng, v ang c p dng cho tuyn hm o C - tnh Ph Yn). V ba l,

phng php khin o ( TBM-Tunnel Boring Machine), phng php ny s

dng cc my o t ng thng c tit din trn, o t t ng v vn

chuyn t ln theo mt ca thng vi bn trn. y l phng php thi cng t

gy nh hng n mt bng bn trn, trong khi thi cng o hm bn di, cc

hot ng bn trn nh i li vn c m bo. phng php ny s dng ch

yu cho o hm trong t yu.

Vi u im trn, phng php ny c la chn xy dng tuyn Metro

u tin ca thnh ph H Ch Minh tuyn t Bn Thnh n Sui Tin.

Tuyn metro ny i xuyn trong lng thnh ph, i ngm bn di v xuyn qua

cc cng trnh trng im nh trong iu kin a cht tng i yu. Mt s

u im ca phng php s dng my TBM o hm trong thnh ph:

1) Phng php ny s dng cc my TBM o t, mc c gii

ha cao do hn ch c tai nn cho cng nhn xy dng cng

trnh.

2) Ty theo loi a cht ni t cng trnh, c kho st trc m

tnh ton loi dao ct t ph hp, trnh lng ph.

3) Hn ch va p vi cc cng trnh trn mt t

4) Thn thin vi mi trng, t gy n o.

Thi cng hm bng my TBM, c nhiu vn cn phi quan tm v y l

mt bin php mi v tng i phc tp v cng ngh. Hn na, y l ln u

tin p dng Vit Nam. Cc yu cu phi tnh ton trong thi cng hm bng

my TBM. u tin, vic kho st a cht mt cch chi tit l rt cn thit, t

kt qu kho st a cht, cc k s s tnh ton thit k v la chn phng n

cho vic ch to my o. Vi a cht nht nh la chn loi dao ct nh th


no cho ph hp. La chn phng thc chng cho p lc ti mt ct ca

hm trong qu trnh o, ty theo a cht m c phng n ph hp. Nu a

cht tt c th thi cng vi h chng t nhin vi iu kin ng hm nm

trn mc mc ngm ( dng khng c mt chng hoc s dng s n nh

mi dc), cc gii php cn li s dng trong trng hp ng hm nm bn

di mc nc ngm nh h chng s dng kh nn, va lng hoc hnh

thc cn bng p lc t bng cch trn phn t mi o vi va ( v d nh

bentonite).

Tuy nhin, bn cnh cc u im trn, cc nhc im chnh ca phng

php ny bao gm:

1) Tn nhiu thi gian chun b v trang b my o

2) Kh khn v tn km cho vic chun b cng trng.

3) Nguy him khi thi cng trong t thay i a cht ln

4) Thng thng ch s dng cho hm c mt ct hnh trn, kh p dng

cho cc tit din khc.

5) Vic thay i tit din trong qu trnh thi cng cng nh vic m rng

hm s gy nhiu tn km v tin bc.

6) C th gy ln mt t bn trn.

Trong cc nhc im trn, nhc gy ln st mt t bn trn gy nh

hng ln n cc cng trnh bn, nht l khi tuyn metro s 1 ca thnh ph

H Ch Minh i qua cc cng trnh mang ngha lch s, chnh tr. Vic nghin

cu cc nguyn nhn gy ln v sut phng n hn ch cc chuyn v bn

trn mt t l vn rt quan trng. Do , bi nghin cu ny tp trung

sut phng n hn ch bin dng ca t nn trong vic thi cng o tuyn

metro s 1 bng my TBM.

Tuyn metro Bn Thnh Sui Tin l tuyn ng hm i qua khu vc

a cht yu ca thnh ph H Ch Minh. Cn c bin php gia c t trong qu


trnh thi cng cng nh khai thc nhm hn ch ti a nh hng n cc cng

trnh hin hu bn trn. i vi a cht yu, v mc nc ngm cao ca khu

vc, s dng phun va p lc c xem l gii php mang li hiu qu cao v

phun va thch hp cho vic ci thin t yu v nc ngm cao c th hn ch

s co ngt ca va phun. Khi , vic nh gi chnh xc hiu qu s dng va

phun trong thi cng o hm trong t yu bng khin c ngha quan trng

quyt nh s thnh cng ca tuyn metro s 1 v cc tuyn v sau ca thnh

ph.

2. TM TT TNG QUAN:

Hin nay, mc d cng ngh thi cng hm bng my o TBM c

ci tin rt nhiu nhng cng khng th gii quyt c trit vn ln b

mt t nn. Vic trt cc lp t hoc thay i cc lp t nn bn trn xung

quanh phn khng gian rng ngay pha sau my khin dn n s chuyn v v

ln st t nn. Mt s nguyn nhn gy ln t nn trong qu trnh thi cng

o hm bng khin o c Bernhard Maidl tng hp trong (1):

- Vic h mc nc ngm trong t dn n s thay i th tch v cu

trc t

- Thay i p lc t ti b mt khin do phn t b mt pha sau my

o

- H ging chng khng m bo cho s mt nhiu t ti b mt hm

- S thay i cu trc ca t do s run ca my o lm cho t xung

quanh b nn li, cng vi h ging khng ph hp vi nn cht ca

t.

- Do khi phun va p lc cao gy ra cc l rng m khng c b lp

- V cc ti kh trong t l gim tit din hm do s gia tng ca p lc

t ln h ging chng.


Hnh: cc nguyn nhn gy ln t nn bn trn hm

Da trn cc tnh cht ca cc loi my o khc nhau, Peck (1969)

xut gi tr xp x cho tng loi t tnh ton b rng trng bin dng

t nn.

Hnh: quan h gia su t hm v b rng vng trng ln

Tc gi Fang (64) xut mt cng bn kinh nghim tnh bin dng

ln nht bn trn ng hm c thi cng bng my o cn bng p lc

t (EPB machines).

axm

ts

a bt


Trong :

t: thi gian c tnh bng ngy

a, b: l cc hng s c tnh ton cho tng cng trnh ring bit

bng phng thc o lng.

Nghin cu thng s b rng trng bin dng, nm 1982, OReilly v

New xut cng thc tnh:

o oi kz

Trong khi , Clough v Schmidt (1981) xut tnh io nh sau:

0.2 0.80.5o oi D z

Nm 1995, Moh v Hwang xut cng thc tnh io theo cng thc

m

oo

zi bD

D

v

m

oz o

o

z zi i

z

Nghin cu cc gii php hn ch ln nn t bn trn ng hm, cc

nh nghin cu tp trung vo vic gii quyt 2 nguyn nhn chnh gy ra ln

l: h nc ngm xung quanh cng trnh v cu trc t nn trong khu vc.

- hn ch vic h mc nc ngm trong khi o hm, ngi ta s dng

cc gii php chng (lining) ti mt o hm v phn rng (hm va o)

do my o to ra sau khi i qua, khng cho nc ngm trn vo bn trong

hm.

- Thay i cu trc ca t nhm tng kh nng chu lc ca t. S dng

cc bin php x l t yu, tng s n nh ca t hoc hn ch s thay i

cu trc n nh ban u ca t.

Tuy nhin hiu qu s dng h chng li ph thuc vo cu trc kt

cu t xung quanh ng hm. Nu trong sut qu trnh thi cng hm kt cu

ca t xung quanh hm khng hoc t thay i, th hiu qu s dng h chng

rt tt. Tuy nhin, nu cu trc t quanh hm thay i, dn n p lc t


tc dng ln h ging ln, v nu h chng khng cng chng li s gia

tng ng sut, dn n h chng b bin dng.

Do , vic hn ch c s thay i cu trc t quanh hm s cho

hiu qu cao trong vic gim s nh hng ca qu trnh o hm n cc

cng trnh bn trn. Jet-grouting ( phun va p lc cao) c nhiu tc gi

xut s dng hn ch s thay i cu trc t quanh hm nhm tng kh

nng n nh ca t nh Thomas v Gunther (2005), Coulter v Martin (2005

v 2006), Yue-wang Han, Wei Zhu, Xiao-Chun Zhong v Rui Jia (2007). Tuy

nhin, trong (1) page 20, cc tc gi Maidl, Anheuser v Gipperich cho rng

phun va p lc cao cng l mt nguyn nhn gy ln st cng trnh, v khi

va ng cng s co ngt to nn mt khong trng xung quanh phn va

ng, dn n t st xung lp y cc phn rng v gy nn bin dng

mt t bn trn.

V vy, cn thit nghin cu hiu qu s dng phun va p lc trong

vic hn ch nh hng qu trnh o hm n mt t cng nh cc cng

trnh bn trn. Trong , cn k n cc yu t khc nh s co ngt ca va

phun, mt phun va, cp phi va v p lc phun va.

3. NG LC NGHIN CU:

Da trn kt qu phn tm tc tng quan, cc tc gi Babank v

Morteza (2008) cho thy c mi quan h gia p lc khi phun va p

lc v cc c tnh ca t. Trong khi , nhiu tc gi khc cp n hiu

qu s dng phun va p lc trong vic hn ch bin dng t nn trong qu

trnh thi cng hm s dng my o TBM nh Thomas v Gunther (2005),

Coulter v Martin (2005 v 2006), Yue-wang Han, Wei Zhu, Xiao-Chun

Zhong, Rui Jia (2007).

Tuy nhin, trong cc nguyn nhn gy bin dng mt t trn ng

hm th s co ngt ca va phun khi ng cng cng l mt trong nhng


nguyn nhn quan trng. Phun va p lc cao va l bin php hn ch s

thay i kt cu t v hn ch s bin dng cng trnh bn trn, li va l

nguyn nhn gy ln st t nn sau khi ng cng.

iu ny m ra mt vn l nh hng ca p lc phun va n hiu

qu hn ch ln st cng trnh bn trn ng hm nh th no, khi k n

s ln st t nn do co ngt va phun? nh gi chung hiu qu s dng

phun va p lc trong vic hn ch bin dng t nn c k thm cc yu t

khc nh p lc va phun, s co ngt va (so vi cc yu t c cp

trc y nh cng , cp phi, bin php thi cng va phun v cao

nc ngm so vi cc thanh va phun) c ngha quan trng trong vic la

chn gii php hn ch nh hng ca vic thi cng hm n cu trc t

nn v cc cng trnh bn trn.

4. MC TIU NGHIN CU

Trong ni dung bi nghin cu ny tp trung phn tch kh nng ng

dng phun va p lc cao jet grouting vo trong vic hn ch bin dng

ca t nn bn trn ng hm trong qu trnh thi cng v khai thc hm.

Tm ra mi quan h gia hiu qu s dng va phun trong vic hn ch

chuyn v t nn bn trn v p lc s dng phun va c k n s nh

hng do co ngt ca va phun sau ng cng. S co ngt ny cng l

nguyn nhn lm bin dng t nn. xut ca mt phng thc s dng

hiu qu h va phun trong vic hn ch bin dng t bn trn khi thi cng

o hm bng phng php khin o cho mt loi t nn c nh.

5. PHNG PHP NGHIN CU:


Da trn c s l thuyt tnh ton hiu qu hn ch bin dng hay s

thay i cu trc t nn t s dng phun va p lc (jet grouting) trong thi

cng hm bng my o c cc tc gi nh Thomas Gunther v Coulter

nghin cu. Da trn mi quan h gia p lc va phun v s thay i cu

trc t, cc quan nim tnh ton co ngt ca va c s dng

S dng phng php phn t hu hn (FEM-finite element method)

phn tch hiu qu s dng bin php phun va p lc cao trong vic hn

ch bin dng t nn trong qu trnh thi cng o hm bng my TBM. C

th, bi nghin cu s dng phn mm Plaxis 3D Tunnel m hnh nh

gi mi quan h gia hiu qu hn ch ln ca h va phun vi p lc cn

thit phun va v mt s dng cc thanh va phun c k n bin dng

t nn do nh hng ca s co ngt cc thanh va phun sau khi ng cng.

Da trn cc kt qu v nh hng ca p lc khi phun va n vic thay

i c tnh c, ca t ca Babank v Morteza (2008). ng thi da trn

kt qu nh gi hiu qu hn ch ln b mt khi thi cng hm s dng va

phun ca Coulter v Martin (2005).

Cc s liu s dng trong bi nghin cu c ly t d n tuyn metro

Bn Thnh Sui Tin, tuyn metro u tin ca thnh ph H Ch Minh.

Cc s liu s dng bao gm: a cht khu vc thnh ph dc theo chiu di

tuyn, thit k kt cu hm, cc gii php hn ch ln c cc nh thit k

cp

6. GII HN TI:

Ni dung lun n tp trung phn tch mc nh hng ca vic o

hm n s bin dng t nn bn trn cng nh cc cng trnh hin hu cho

tuyn metro s 1 ca thnh ph H Ch Minh, tuyn u tin s dng bin

php thi cng bng my o TBM. Tuyn metro ny i qua vng a cht


yu v tng i phc tp, i ngay bn di cc cng trnh quan trng ca

thnh ph.

Phn tch c im a cht khu vc thnh ph m tuyn hm i qua.

S dng gii php phun va p lc hn ch s bin dng trn. Tuy nhin,

bi nghin cu tp trung phn tch hiu qu hn ch bin dng t nn c k

n hin tng co ngt ca va phun sau khi ng cng, iu ny lm gim

hiu qu hn ch ln ca va phun. Tm ra c mt p lc phun tt nht

cho hiu qu chng ln i vi a cht khu vc thnh ph H Ch Minh dc

theo tuyn metro Bn Thnh Sui Tin.

7. KT QU D KIN:

Tm ra mi quan h gia p lc phun va v hiu qu hn ch bin

dng t nn bn trn cng trnh hm thi cng bng phng php khin o.

Trong , c xt n s co ngt ca va phun khi ng cng nh l mt

nguyn nhn gy ln t nn. nh gi mi quan h trn v tm ra p lc

phun ti u cho hiu qu gim ln tt nht ng vi a cht khu vc tuyn

metro s 1 ca thnh ph H Ch Minh.

cng Lun vn Thc s GVHD: PGS.TS. L Vn Nam

TS. Trn Nguyn Hong Hng

HVTH: Nguyn Tng Thanh Bnh - 11 - MSHV:09380982

8. CHNG TRNH D KIN:



9. TI LIU THAM KHO

1. Bernhard Maidl, Martin Herrenknecht, Lothar Anheuser, Mechanised

shield tunnelling 1996.

2. Fang, Y.S. Time and settlement in EPB shield tunneling, Tunnel and

tunnelling 25 (1993)-64

3. Sozio, L.E., Settlement in Sao Paulo shield tunnel, Tunnel anf

Tunnelling 10 (1978)-177

4. Thomas Kasper, Gunther Meschke, On the influence of the face

pressure, grouting pressure and TBM design in soft ground tunneling,

Tunnelling and Underground space technology (2005)

5. S. Coulter, C.D. Martin, Effect of jet-grouting on surface settlements

above the Aeschertunnel, Switzerland, Tunnelling and Underground

space technology (2005)

6. Babank Nikbakhtan, Morteza Osanloo, Effect of grout pressure and

grout flow on the soil physical and mechanical properties in jet-grouting

operations, International journal of Rock mechanics and Mining

sciences (2008)

7. Shao-Ming Li-ao, Jian - Hang Liu, Ru-lu Wang, Zhi-Ming Li, Shield

tunnel and environment protection in Shanghai soft ground, Tunnelling

and Underground space technology 24 (2009)

8. S. Coulter, C.D. Martin, Single fluid jet-grout strength and deformation

properties, Tunnelling and Underground space technology 21 (2006)

9. K.M. Neaupane, N.P. Adhikari, Pridiction of tunnelling induced ground

movement with multi-layer perceptron, Tunnelling and Underground

space technology 21 (2006)



10. M.A. Meguid, O. Saada, M.A. Nunes, J. Mattar, Physical modeling

tunnel in soft ground: A review, Tunnelling and Underground space

technology 23 (2008)

11. Suchatvee Suwatsawat, Herbert H. Einstein, Artificial neural network

for predicting the maximum surface settlement caused by EPB shield

tunneling, Tunnelling and Underground space technology 21 (2006)

133-150

12. C.J. Lee, B.R. Wu, H.T. Chen, K.H. Chiang, Tunnel stability and arch

effects during tunneling in soft clayay soil, Tunnelling and Underground

space technology 21 (2006) 119-132

13. Chungsik Yoo, Joo-Mi Kim, Tunneling performance prediction using an

integrated GIS and neural network, Computers and Geotechnics 34

(2007) 19-30

14. Ebrahim Farrokh, Jamal Rostami,Effect of adverse geological condition

on TBM operation in Ghomroud tunnel conveyance project, Tunnelling

and Underground space technology 24 (2009) 436-446

15. Z.C. Moh, Daniel H.Ju, R.N Hwang, Ground movement around tunnels

in soft ground, Int. Symposium on Geotechnical Aspects of

Underground Construction in soft ground (1996)

16. Warren Wangryul Jee, Sang-Gui Ha, Feasible boulder treatment method

for the soft ground shielded TBM, Underground space (2007)

17. Yue-wang Han, Wei Zhu, Xiao-Chun Zhong, Rui Jia, Experimental

investigation on backfill grouting deformation characteristics of shield

tunnel in sand, Underground space (2007)

18. G.M. Volkmann, W. Schubert, Geotechnical model for pipe roof

supports in tunneling, Underground space (2007)



19. Akchiche Mustaqua, Barha Ramdan, Some Algiers experience on

measurement and evaluation of settlement around urbane tunnel

reinforced with jet-grouting, International Journal of Theoretical and

applied Mechanics ISSN (2008)

20. Gunther Meschke, F. Nagel, J. Stascheit, T. Kasper, Advanced

numerical silulation of shield tunneling and its role in the design

process, ECCMAS Thematic Conference on Computational methods in

tunneling (2007)

21. Julio B.Martins, A short survey on construction problems and

numerical modeling of shalow tunnels

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