Tinh toan cong trinh ngam tiet dien ngang hmh chO nhat dat nong trong moi triF^ng dat mem chju tac dong cua dong dat
Earthquake Design of Shallow Rectangular Underground Structure in Soft Soil
Ngay nhan bai: 15/10/2014 Ngay sCra bai: 22/12/2014 Ngay chap nhan dang: 5/01/2015
Le Bao Q u d c
T O M TAT,
Bai bao phan tich, trinh bay cdc phtfong phap giii tich, phUcrng phap dUa chuyen vi cua nen dat vao bien va phifOng phap pho gia toe nen de tinh toan cong trinh ngam tilt dien hinh chii nhat ddt ndng trong mdi trddng dat m i m chiu t i c ddng ciia dgng dat.
TU k h d a : phan tich tai dong dat, cong trinh ngslm, phuong phap pho gia toe n i n , chuyin vi.
ABSTRACT
Analysis, presentation of analytical methods, finite element Seismic deformation method (FSDM) of groimd motion put on the boimdary and groimd response acceleration method (GRAM) to calculate the underground section shallow rectangle set in soft soil under the mfluence of earthquake.
Keywords: Seismic analysis, underground structure, ground response acceleration method, displacement.
Ncs. Le Bao Quoc.
Vi6n Ky thu^t c6ng trinh dac bi?t, Hoc vien Ky thuat Quan sy
Di dpng: 0918.999.777 Email: quocvn21 (gyahoo.com
l . G i d i thieu.
He thong Metro dang duac xay dUng 6 Ha Noi vaTp. HCIW nim trong m6i trudng d^t mem c l n duoc tinii toan chiu tic dong cua dong dat Khac vdi cong trinh noi hien tai Viet Nam chua ban hanfi tieu chuan tinh toein thiet ke c6ng trlnti ngam chiu dong dat n6i chung va eong trinh ngam trong moi trUdng dat mem ehiu dong dat noi neng. Do vay, viec nghien euU lUa chgn phuong phap t i n h cong trinh ngam trong moi trucjng dat mem la can thiet Nhieu nha nghien cuu ichoa hoc tren the gicn da nghien cdu phuong phap t i n h to^n cong trinh n g i m chiu d6ng datva de xuat cac phUOng ph^p tinh B i i bao dUfJi day trinh bay cIc phuc*ng phSp:
Phan tich g i l l tfch;
Bien dang cua nen (FEIVI Seismic Deformation Method - FSDM);
Pho gia toe nen (Ground response Acceleration Method - GRAM);
Dong thdi phan tieh so sanh giijfa eae phuong phap va de xuat pham vi Ctng dung cilia eie phuong phap tren trong tinh toan thiet ke cong trinh n g i m trong moi trUcmg dat mem chju dong d i t
2. Anh hudng ciJia ddng dat doi vdi cdng trinh ngam hinh hdp chu'nhat v l sUkhac bi^t so vdi cong trinh ngam hinh tron.
Cong trinh ngam hlnh chO nhat, nha ga thudng dat ndng va duac xay dung theo phUcJng phap dao hd va lap d i t t r i lai. Khac vdi tuyen chay tau thudng co tlet dien trdn v a d dd
V. = R.Air
sau ldn, cac cong trinh ngam tiet dien tlet dien hinh) ch i l nhat cd nhCfng dac d i l n sau.
Cdng trinh ngam hlnh chij n h i t dat ndng n^n ed nhuoe diem hdn cdng trinh ngam hinh tru tron dat sau d o cUdng dp rung l i e ngang va bien dang cua d i t nen Idp tren Idn hOn Idp dudi, do d d do cu'ng cilia d i t xung quanh ham be.
Hinh dang, kich thUdc cdng trinh n g i m hlnh chu' nhat thudng Idn hem cdng trinh ngam hinh tru trdn, nen t l i trong tinh t i c dung len ket e l u khae, Vi the ket eau tam, tUdng thudng d i y va CO dp cdng Idn. Do dp cdng cao hon va h i l n dang nen idn hon nen c l n xet den tUong tac gida ket e l u va mdi trUdng nen xung quanh, D o e o n g n g h e t h i c d n g d a o h d v a l a p d a t lai nen cac tham sd cua d i t d i p t r i c l n nghien edu trang thiet ke cdng trinh ngam.
3. Phiftfng p h i p tfnh cdng trinh ngSm hinh chd nhat chiu t i c ddng dong tfcit.
Khi ddng dat x i y ra tao ra song lan truyen trong mdi trUdng dat tac dyng len cdng trinh ngam, Cac bien dang trUdt cua dat xuat hien do ian truyen sdng e l t theo phuong t h i n g ddng I I dang ehiem uu the cda chuyen ddng do ddng dat g i y ra, Vdi t i n h c h i t da dang vh phdc tap eua t i c ddng ^ a chan len edng trinh ngam dat ndng dUoc xay dUng bang phuang p h i p dao hd, ehieu sau nhd, nen luc q u i n tinh, dng s u i t va bien dang do tac dpng dia chan Idn hon nhieu so vdi khi dat sau.
Cae phuong phap tinh t o i n edng trinh
r*, Is
L S f l d d t i n i t t r U o t ami gian doi vOi ham tiet dien ngang hmh chii nhal
6!
ngam chiu tac dung ddng dat dUOe eie nha khoa hoc nghien cdu nhu; phucmg phap t l i tinh tuOng ducmg, phuong phap dat chuyen vi d i t nen do t i c dung ddng dat vao ket cau cdng trinh n g i m va phuong p h i p pho gia tdc nen (fulldynamie)[2],[31,
3.1 Phddng phdp t l i tinh tUdng dUong.
Theo Wang nam 1991 [2], v l sau d d dUOe Penzien va Wu [3] da p h i t tnen g i l i p h i p phan tich tuong t u de x l c d m h md men udn v l luc e l t trong v6 ham bien dang do ddng dat.
PhUOng p h i p dUde trinh b i y qua c i c budc nhu sau:
Xac dinh cac tham sd dae trung l „ ddng ciia nen dat thdng qua thi nghiem CPT, SPT t4],[S].
Xac dinh c i c W tham sd ddng dat n h u gia toe dinh, van tdc dinh va chuyen vi dat dinh t d c i c ngudn vien v i t 1^ dja cau, ti^u chuan. CIc gia tdc dinh dUcKxIc djnh theo b i n do p h l n bo vung dia chan va hieu chinh theo k h o i n g c i c h ddng dat g i y ra. Til PGA c6 the xac djnh dupc PGV va PGD theo b l n g 1 [6],
Do eudng dp dao ddng cOa dat nen g i l m dan theo c h i l u sau, nen e i c tham sd tUong quan cung g i l m d i n phu thudc v i o c h i l u sau dat ham, xac d m h theo b l n g 2 [7].
B i l n dang euc 6^\ trUdng tU do ctia dng suat trUcrt nhu sau: [2]
m/s;
b d&C^ la van tdc lan truyen sdng e l t ,
Trong d d . A - bien dang truOt g i y nen bdi lUc tap trung 1 dem vi.
Td he sd do cdng chiu uon x l c dinh t d bi^u thdc (3), cd the t i m duoc hd sd d d cdng khi trirgi:
" bien dang ciia trvimg tv do phia tren ket ci V ia van toe dinh e h u y l n ddng, m/s.
Xac dinh bien dang ^ . . ^ ^^^^^ ^^ ^g^ dun^m trong dat cua nen theo chieu eao / J ^ = =-
ham,
' *^'
Trong d6:Y „ - b i l n dang chuyen v] trong mien t u d o cua n i n .
H - c h i l u cao ciia mat cat ngang h i m . He sd dp cdng chiu uon cua k i t cau dang hop x l c djnh theo cdng thdc [2].
^diff -(5)
Ks H ,(3) Trong dd:
W - Chieu rdng det d i f n ngang cua vd ham, m;
H - Chieu cao t i l t dien ngang v d ham, m, G - Md dun b i l n dang trUcJt trung binh cda dat nam trong pham vi t d dinh den d i y ham tuong dng g i l t n eae dng s u i t , N/m2;
Kj - Od cdng k i t eau vd ham hinh ehd n h i t khi trUcrt la nghich d l o cda bien dang trUcrt ben do duoc gSy ra bdi mdt ddn vi li/c tap trung,
K - ^
^ ^ " A (4) B l n g 1. B l n g tra t y s
Cap d&ng dat, M ^
Oat da rat cdng 6,5 7,5 8,5
6 gida v i n tdc dat dinh va gia tdc dinh [6]
Tl sd gida g i l tri v^n toe chuyen dong dat dinh cda dat da [cm/s) tr€n g i l trj gia toe chujen ddng dat dinh <^a M t 6a(g); PGV/PGA
K h o i n q eieh t d qde ddng dat d i n cdnq trinh, (km) 0 - 2 0 1 2 0 - 5 0 1 5 0 - 1 0 0
66 97 127
76 109 140
86 97 152 Oat da cdng
6,5 7.5 8,5
94 140 130
102 127 188
109 155 193 Oat da m i m
6,5 7,5 8,5
140 208 269
132 165 244
142 201 251 Bang 2, CIc he so x^t den sU g i l m dan cua cae tham sd d i e trUng c h u y i n ddng cua dat theo c h i l u s i u .
Chieu sau dat h i m , (m)
•S 6 Td 6 -1S T d l 5 - 3 0
He s6 xit den sU g i l m dan eua cac tham so dac trung chuyen ddng eua dat nen phu thudc vao e h i l u s^u dat ham
1,0 0,9 0,8
> 3 0
B l n g phuong phap p h l n t d hdu han Wang v l Penzien ed ldi g i l l trong dieu kien ttuat toJn bd v l khi khdng t 6 n tai trUcrt [2]. PhUdng phip g i l i tich cho k i t qua t u o n g ddi g i n vdi cae ket q u i nhan ddoc khi sd dung phuong p h i p phan t d hdu han. Do v i y , cac tUong quan tren cd tlie sd dung d l danh g i l bien dang trUcrt eua ham hinh c h d nhat trong sU phu thuoc vao tUong quan xac dinh theo p h u o n g trinh (2).
Khi t u o n g t i c khdng co trUpt:
R ^ = l < ! j 2 5 l ^ (61
Khi tUcJng t i c cd trUOt toan bp:
"" 2.5-3v^+fr' ffl X l c dmh gia trj b i i n dang trUdt cua k i t cSu
A c d t h e x l c dmh khi sd d y n g t i / o n g quan:
A^=R,Aji^ (81 X l c d i n h n ^ i idc va d n g s u i t cCia edng trinh
n g i m duoe x l c dinh tr^n ehuyen vi cho t r u d c i tUdng dng vdi so do tfnh the hien tren hinh 3.
TrUdng hdp t i n h t o i n ddng dat vdi t l i trpng theo phddng ddng, t l i trong tinh tac dung len k i t eau cdng trinh n g i m dupe t i n h b l n g 2/3 X [ ( h i sd ddng dat theo p h u o n g ddng) x (tong cic luc tinh theo phuong ddng -i- cae tinh t l i khac)]
3.2 PhUdng phap bien dang ciia dat n^n (FSDM - FEM Seismic Deformation Method):
a. Phuong phap d i i n g Id xo thay the tirang tac cua k i t c l u - mdi t r u d n g .
Nam 1984, Hamada [8] dung Id xo thay th*
t u o n g tac cda k i t c l u - mdi trUdng. l/u di^m cua phUdng phap nay ia m o p h d n g dedangra tinh t o i n d o n g i l n (hinh 4). ' ' '
b, Dat bien dang cua trUdng tU do eiia nen vao m i l n bien
Trong bai bao nay eac t i e g i l dung phuong phap dat b i l n dang "trudng tU do" cua nen dat
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a ) Lire t a p t m n g t u a t m h d o i \ cti b) P h a n b o a p lire t u a t i n h t a m g i a c d o i \ c o n g trinh n g a m d a t s a u c o n g trinh n g a m d a t n o n g Hinh 3. So da tinh tniot don gian d6i vA c£ng trinh ngam tiet dien ngang hinh chO nhat
Trudng ta
I|V-A1|||\AM'i
(giay) 5 . ( t ) = u , ^ ) " " " i * - u . ( t ) ' » * > '
(gfay) Hinh 4 So do tinh theo Hamada dung cac 16 xo thay the ti/ong tac cua l(et cau v ^ moi tru'dng.
ilSlduMjIoii!*
, piling Jf*
r00,
TTZZjdi^
(FSDIUI - FEIVI Seismic Deformation Method) vao mien bien ciia m i l n k h i o slt d l xlc dinh b i l n dang trUpt ciia k i t cau ham thdng qua phuong phap p h l n t d hdu han nen khdng can thiel xac iJnh vi thilt lapclc lo xo thay t h i dat n i n xung quanh,
Phucmg p h i p dat b i l n dang ciia trudng t u do vin m i l n bidn - FSDM c l n c d vSo b i l n dang cUc dai "trudng t U d o " cua nen. Sau dd x l c dinh v l dat chuyen v\ tUong ddi (A^^) t h u dUoc vao mien bien n g o i i cda md hrnh FEM t h i hien dat xung quanh ham. CIc dat xung quanh dUOc mo hinh hda vdi eie phan t d hdu han de nghien cdu sU on (finh dja chan cda dat xung quanh cdng n h u k i t eau ham. Mo hinh c6 t h i mo t l n h u hinh sau.
3 3 PhUcmg p h i p pho gia toe nen theo thdi gian.
CIc phucmg p h i p duoc trinh bay d muc 4 2 thuc c h i t la phUdng p h i p lUa tinh chUa danh gia duoc so do lam viee thUc cua k i t c l u chiu t i c dung d ^ n g d i t . Phan dUdi d i y se t n n h bay phuong p h i p ph6 gia tSc nen d l tinh cdng trinh ngam chju d ^ n g dat. Phd gia tdc n i n dUpc dat vao d i y md hinh tinh t o i n , v l cac bieu do
gia tdc ddng dat theo ham i h d i gian dUdc cac n h i dia chan ghi lai bang thiet bi sau cac tran ddng dat (bang ghi pho gia tdc, file dang '.smc hay txt). So do tinh k i t c l u n g i m ehiu t l i trpng ddng dat theo dupc m d t l n h u hinh 6.
4. Nghien cdu t h d nghiem so va so sanh gida cac phuong phap tinh.
o l nghien cdu img x d gida n i n dat v l cdng
gian dUde eic nha dia chan ghi lai dang file (*.smc). Sd dung phan m i m Plaxis V83 de giai bai t o i n tuong t i e k i t e l u vdi mdi tru'dng n h i l u Ic^, cie tham sd mdi trudng cho trong b l n g 4
CIc phuong p h i p nghien cdu t i n h t o i n dupc dien t l nhU b l n g sau:
Trong b l i b i o , t i e g i l chon cdng trinh n g i m cd cao do t h i l t ke tinh t d mat dat -12,09m, k l l Phuong phap
Grii tich theo Wang va Penzien C h u y i n vi cda n i n dat
(FSDM) Phuong phap pho gia tdc n i n [Full dynamic)
M o t I
Xae dinh cac tham sd dong eiia n i n v a tinh toan theo cac ly t h u y l t ciia Wang va Penzien (1998)
Dat chuyen vi Idn nhat ciia n i n dat do tac ddng cua ddng dat vao hai bien ddnq ciia md hinh tinh
Dat t i l trpng cua ddng dat phia dUdi md hinh nen tinh toan. sd dung file ghi dC^ heu ddng dat
trinh ngam c a c t a c g i a s d d u n g b a phuong phap nhU: phan tieh giai tich, phuong phap bien dang trudng tU do ciia nen, v l p h l n tieh phi tuyen theo lich sd t h d i gian (full dynamic) cho cimg gia tdc dinh la 0,24g.
Phuong phap so sd dung b l n g ghi gia toe nen n h u hinh 7 dUoc dat vao day md hinh tinh t o i n , bieu dd gia tde ddng d i t theo h i m thdi
cau h i m gom 2 dang mat d t chdnhaL Dieu kien dia chat theo cae chi tieu co ly cae Idp d i t nhU b l n g 4 va cat lap lai sau khi thi cong xong cd y = 20kN/m^ E = 3.000 kN/m3, v = 0,3, (p = 300
K i t c l u ham bi tdng cdt t h e p dUdc xem la dan hdi va b d qua ty sd c l n cua be tdng ham.
Chi t i l t e i c thdng sd ciia h i m cho trong b l n g 6 5. Ket q u i tfnh toan minh hoa dat dUdc.
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ifinh 7. Ban ghi gia toe n^n dSng dat tifflng dUOng 0,24g, ngay 28/02/1990, llh43'M'' PM d i / « tich hop sin &ong phSn mem Plaxis.
So i M i ^ l i ^ da phuonn phip Ibli
ifinh S 3)Scid6hinhlioc,b)sacl6tinh,vac)'>iendangcuanJndiifcditjai>dttuluenbiajuHh«ip.
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., bien,saisagiitaphuongphapgijitidiWang-PhilOngphJpphlS f gia toe nen va sai so giDa phUOng phap chuyen vl biln - Phuong
ph j p pho gia toe nen.
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Hmh6 alSodohmhhocvablsodochialuoiphdntiJkhidujphdgiatScnfntheotl^granvaa-mSimriing,
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Chi chd; MCC: Mo hkh Cua-Cb) tU hiii MC-. Mo hkh Mohr-Coalonb K i t q u i tinh toan cdng trinh ngam hinh c h d n h | t chiu t i e dung d d n g dat ed gia tde nen 0,24g t u o n g dng c i c phuong p h i p g i l i tich v l phdong p h i p s6 ( b l n g 7).
K i t l u i n .
Qua k i t q u i p h l n tieh cac phuong p h i p
Iinh t o i n cong trinh n g i m hlnh c h d nhat dat ndng thi cdng dao hd trong mdi trUdng n i n dat y l u ehiu t i c dong dong.
PhUdng phap g i l i tfch theo Wang v l Penzien eho g i l trj ndi lUc vd ham ldn. Phuong p h i p tinh t o i n bien dang m i l n t u d o ciia nen
Kinh 9. So do chuyen vi, bieu do lUc cJl vi Mo men vi him trudng hop gili bang phuong phap dat chuyin vl trudng tudo v^o biln (trucmg hop I(h6ng trUOt],
irnhlO.Sod6chuylnvi,bi^ud6lyccltvaMomenvAhlin tiUcmg hi^ giai bang phUong phap pho gia tdc nen theo thdi gian {trudng hap lihong tn/ut).
dat (FSDM) va phan tich phi t u y l n theo lich sd thdi gian (Full dynamic) cho k i t q u i t d d n g d6\
gan nhau, cd sai sd < 5%.
PhUcmg phap g i l l tich tinh t o i n cho d e
7218
B l n g 6: Kich thudc hinh hoc va c i c tham sd vat lieu cda ham Tham sd
H i m ed kich thudc b/h
0 6 d i y vd hlm(Day, maD, va (tudng, vach ngar) M d d u n dan hdi be t d n g vd ham He sd Poisson be tdng
G i l trj 20/6 1,0/0,8 3,5£-l-7 0,2
Dc^nvj
m m kN/m^
B l n g 7 . K i t q u i tinh toan theo hai mdl t r u d n g n i n khac nhau vasUsailech Ten PhUcmg p h i p
G i l i tich theo Wang va Penzien FSDM
Phuong p h i p pho gia tde theo gian
Khong trUot TrUOt toan bd
Khdng trUct R,n.= 0,8 Khdng trUot
R,nl=0,8 (KN/m)
l,46E-(-3 1.S7E+3 1,33E-i-3 l,33E-l-3 l,36E+3 1,37E+3
(KN/m) 0,890E+3 0,954E+3 0,661 E+3 0,681 E+3 0,696E+3 0,70SE+3
(KNm/m) l,73E+3 1,85 E+3 1,14E-H3
1,14E+3 l,lSE+3 1,17E-(-3 trudng h i ^ k i t c l u dem g i l n , moi trudng l phuong p h i p
Idp, ddi vdl t r u d n g hop phdc tap mdi trudng toan k h i o sat;
n i n n h i l u Idp p h l i qui doi ve ldp tUong dUOng phdc tap yeu khdi lucmg t i n h toan rat ldn k i l n nghi sd d u n g phuong phap
g i l i tich eho cac trUdng hop tinh
;o bd ban dau; ddi vdi trUdng hop e l u ehinh xac cao nen sd d u n g sd tinh toan.
T A I U E U THAM KHAO
1. Tieu chuan Quoc gia 9386:2012 Thiet i(e cdng trinh chiu dong d a t
2, Wang, J. 1993, Seismic design of tunnel, Monograph 7, ParsonsbnnckerhoffQuadefidouglasInc.NevfVori: June 1993.
3, Penzien, J. 2000. Seismically induced racking of tunnel linings. Earthquaiie Engineenng and Structural Dynamics, Vol 29.
4. Schneider J J i , HoyosL, MayneP.W, Macan EJ, and Rix G J . (1999), R d d and laboratory measurements of dynamic shear modulus of Piedmont residual soils. Behavioral Characteristicsof Residual Soils, GSR 92, ASCE, Resion, VA, ^ 12-25.
5. The South Carolina Department of Transportation (SCDOT), Geotechnical Design Manual - version 1,1 (2010) - Chapter 12. Geotechnical earthquake engineering (Final), h t t p : / / www.scdot,org/dolng/siructural_ geotechnical aspx
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