Phipcyng phap tfnh toan cong trinh ngam trong dat mem chju tac dong cua dong dat
Method of calculation of underground constructions on soft soil affected by earthquakes
Ngay nhan bai: 25/12/2015 Ngay site bai: 14/01/2016 Ngay chap nhan dang: 26/03/2016
T O M T A T
Thigt ke khang chan cho cong trinh ngam do thi chiu tai trpng dong, trong do co tai trpng tac dong cua dqng dat la van de quan trpng doi vdi ky sU xay dUng. Hi?n tai cr Viet nam chila c6 tieu chu£n thilt ke khang chan rieng biet cho cong trinh ngam. Bai bao nay trinh bay cac phUOng phap tinh toan thiet ke khang ch&i cho cong trinh ngam va ifng xii cua nen dat khi dong dat xay ra.
TH khoa: cong trinh ngam, dpng dat, phiiong phap tUa tinh,
phvtcfng phap gidn do gja toe, dSt yeu.
SUMMARY
Resistant design for the underground urban dynamic load, including the impact of the load it is important issue of civil engineers. Up to now, Vietnam do not have anti-seismic design standards separately for underground work. This paper presents the design calculation method for the underground shock resistance and the behavior of the ground when the earthquake happened.
Keywords: Seismic analysis, underground structure. Imposed Seismic Ground Deformation, full dynamic, soft soil.
Le Bao Quoc, Vii Dinh Ltfi, Ngo Ngpc Thuy Vien Ky thuat Cong trinh Dac biet, Hoc vien Ky thuat Quan sU.
DD: 0918.999.777 Nguyen Quang Dilng Dai hoc Cong nghiep TP HCM;
Bill Ngpc Dung Dai hoc Dan lap Hai Phong Email: [email protected],
Le Bao Quoc Vu Dinh Ld'i, Nguyen Quang Dung
Bui Ngoc Dung,Ngd Ngoc Thuy
I . D a t v a n d e .
De g i l l quyetvan de giao thong d d t h i tai c l c t h i n h phd Ifln nhir H4 Nolva TP.HCM n h i l u dU I n ve ha tang giao thong nhutaudi^nngam, nha ga ngam, bai d d xe ngam, hay cac trung tam mua s i m ngam dutfc x i y diing nham g i l m t h i l u khflng gian mat d i t . Bay I I cac cong trinh cong cong nen r i t can d i m b i o an tOcin cho ngadi dan cung nhi/ket clu ngam khi x i y ra dqng d i t .
2. Ljch sit phat trien cua tieu chuan t h i ^ k^ khing chan d Viet Nam.
Trudc d i y cd TCXDVN 375:2006 ve thiet ke cong trinh chdng dong dat sau do duqc c h u y i n ddi thanh Tieu chuan Quoc gia TCVN 9386:2012, yeu cau thiet ke cong trtnh chm dong d i t duqc bien soan trgn cosd chap nhan Euroeode 8 co bo sung hoac thay thi eae phan mang tinh dac thu Viet Nam dong thdi ket hop b i n do phan vung dgng dat chu ky lap 500 nam do Vien Vat ly dia cau lap. Tuy nhien, trong Tieu chuan dd van thieu phan quy dinh ve tinh toan cong trinh ngam.
3. PhuWng phap tinh tohn cong trinh ngam chiu tac dong dat trong mdi tri/dng dat mem
Qua nghien cilu va tham khao cac tai iieu ttt cac nha khoa hoc trong va ngoai nUdc, bai bao t r i n h bay cac phuong phap tinh toan cong t r i n h ngam nhU: phUOng phap lUc quan t i n h , phuong phap gia toe ngang t u o n g d u o n g , p h q q n g phap tfng x i l cCia gia toe n4n, p h u o n g phap ap Sat bien dang cua nen dat va phuong phap phin tfch d q n g theo lich sCr t h d i gian.
3.1 Phuqng phap lUc quan tinh
/ l l F^? ?33 ?34
Hlnh 1. Ap luc ngang cua nen datva lUc quan ti'nh tac dung len ket cau PhUOng phap lUc q u i n tinh la phuqng phap don g i i n de tinh toan cho kit cau ngam dang khung v6i lUc duqc flat vao vj tri cac nCit cua khung ket cau m o t l n h u h i n h 1. L u e t i c dung len ket cau gom hai thanh phan: lUc quan tinh va lUc khang ngang bdi d i t nen. Luc quan tfnh tUUrg duong duqc xac dinh theo cdng thise sau:
trong d6;
K c - c h i s 6 l U c k h i n g c h i n ngang;
Qij - khoi luong tap trung tai niit
l72jraniiiEiiHai 04.2016
Phan Idn cac p h u o n g phap, lUc khang ngang dua t h e o su bien dang cCia nen dat. Life khang ngang di/qc g i l dinh theo dang tam g i l c , va c l c g i l tri d u q c xac d i n h t h o n g qua phUOng phap gia toe nen tUong d u o n g :
I P . ' S F , (2)
trong d d :^ P ^ -lltongcCialuCkhangngangtrenmateBtmadiJXbotrinhuhJnhtam^
]^F|, - la t o n g cOa lUc quan t i n h cua k i t cau.
Theo t l l u chuan Trung Quoc cho thay viec tinh t o i n vcfi lUc q u i n tfnh cue dai eho ket q u i gan udi phUOng phap tinh toan dong theo hch sCfthdi gian.
3.2. Phuong phap gia tdc ngang t J q n g d u q n g
Hinh 2. Bleu d6 gia toe nen tUong dUong.
PhUOng phap gia toe ngang t u o n g duong dUa t r i n co sd phan phdi gia toe nen tUa tinh nhU hinh 2 duqc dUa tren k i t qua phan tfch thf nghiem v l t h d i gian lich sCr. Trong mdi t r u d n g dat yeu co anh hucmg k h u l c h dai ve gia t6c v l van toe nen d o dgng dat gky ra[3].
trong do:
H - ehieu day ciia Idp d i t ;
h i , h2 - chieu s i u cCia nop h i m va day ham;
p i , P2 - he so I n h hudng cilia van tde;
0,1 g - gia trj thiet ke cua gia tdc nen ciia tran dong dat co b i n do! vdi cong trinh ngam vdi chu ky 50 nam.
3.4. PhUOng p h i p I p dat chuyen vj cua nen dat v i o bien [Imposed Seismic £ r o u n d Deformation - fSGD).
Cong trinh n g i m chiu tac dung dqng dat khae vdi cdng trinh noi t r i n mat dat. T l i t r o n g tac d u n g vao cong trinh ngam duqc truyen qua sudich chuyen cua nen. Theo phuong phap ISGD dudi tac dung cija song dja chan lam djch ehuyen moi trUdng n l n , t i f day ap dat djch chuyen vho bien d l x i c dinh djeh chuyen k i t cau. C i c h xhe dinh dich c h u y i n ciia nen dat c d t h e n h u s a u :
ChuycDVi A I 3" TZZSCImjeii Ul msi •111 I P ^ 1 — ^ ' i " mai dni
Kinh 3 Mo hinh bai Man khi ^ 1 thuyin vi ciia nen vho bien.
Chuyen vi ciia nen tai bienduqc xac djnh theo bieu thtic sau.
u,=-\-r,s>, (^
trong do:
Se - h a m p h o phan i f n g , duqe x^c djnh dUa theo TCVN 9386:2012, (h, - bien 36 dao d o n g ciia n l n .
n - ik he so tham gia dao ddng t h i f I va dUoc xac dinh theo bleu
r,=<t.>.{d) (4)
vdi Edi la vec t o CO gia t n bang 1 , V e c t a { d } d u n g d e chuyen ma tranM t i f ma tran cheo thanh ma tran cdt.
B i l n dd dao dqng ciia n l n ^.duqc giai tCf phuong trinh sau, t i m duqc trj rieng hay t i n so dao dqng eiia he co dang nhU sau:
{ K - C O ' M ) I ) . = 0 (5) trong do:
ca - la tan sd dao d o n g rieng;
a)' = X- duae gqi la trj neng;
([) duqc gqi la vec t q rieng;
K, M - ma tran do Cilng v^ ma tran khoi lUOng cua c l c ldp dat.
De phuong trinh (5) cd nghiem thi djnh thiJc ciia ma t r i n sau d i y phai b i n g 0:
| K - C O ' . M | = 0 (6) Giai phuong trinh (6) se tim duoe d e gia tri ciia co',tifdd thay v i o phuong
trinh (5) de tim iji. Do v i e c g i l i phuong trinh (6) khi bac ciia to' ldn la khd khan nen trong thUc hanh, eae phuong phap giai lap thudng duqc ap dung de giai phuang trinh (5) de tim duqc dong thc«' cac gia tri ciia oi^ va <ji.
Gia t n eiia (|) duqe tryc giao vdi ma tran khoi IUong theo bieu thiSc.
i|i^M<ti = 1 (7) va do do dan den:
it)^Ki)i = ca' (8) Clc phuong p h i p thudng duqc I p dung la phuong phap lap ngUOc
vec to, phuong p h i p l | p khdng gian con, va phuong phap Lanezos[4].
Ttf thuat toan x i y dUng phan mem"Soil Column Vibration - SCV2015". Chucmg trtnh cd k h i nang tinh toan dao dqng eiia nen d i t khi dqng dat x i y ra va xuat k i t q u i c h u y i n vj, van tdc va gia tdc tai cao do cac Idp dat n l n . K i t quh duqc x u i t ra t i p so lieu dang SCV va la sd lieu dauvao phan mem Plaxis 2D V2010.01 de giai q u y l t b l i toan cong trinh ngam chju tac dung ciia ddng dat.
3.5.Tfnh t o i n cdng trtnh ngam theo g i i n do gia toe (Full dynamic method),
1 1 : . tr: »•
' I : - # ( ( | K ~ — !
len^^^c^
.. a
Kinh 4. Mo hmh tinh ham chiu dpng dat theo giin 36 gia tdc nen
Dudi tae dung eiia tai trong dqng d i t , phuang trinh vi phan chuyen dqng her theo phuang phap gia toe nen theo thdi gian (phuong phap full dynamic) cd dang:
[ M ] { u } + [ C { U } ] [ u } + [ K { u } ] { u } = [ M ] ( ; i \
(9) trong do. {u}g - vec to gia toe n l n do d d n g dat gay ra duqc dat vao tang da gdc.
[M],[C|,[K] -ma tran khdi luqng, cin nhdtva dp eung oia he;
Theo Iy thuyet ddng lUc hoc cOa n l n dat[5] cae ma tran khoi lUOng vat lieu [M] duqc xae dinh bao gom ma tran khoi luqng vat lieu ciia dat nen + nUdc + k i t e l u , Ma tran c i n [C] thUe te kho xae dinh duqc cac tham so c i n eiia k i t cau, dac biet vdi bai toan cd nhieu bac t u d o tai moi n i i t vi eae tham sd can phu thuoc vao tan so dao Song ciia he. Vi vay trong tinh
t o i n ddng lUc hoc t h u d n g gih t h i l t rang ma tran cania t6 hop tuygn t m h cua ma tran khdi luqng [Ml va ma tran do cUng [K] ciia he, thong qua cae hang sd Rayleigh CX.R,PR nhusau:
[q-o,M+ft,[K] (10)
Haihang so can Rayleigh C^R-Prt cd the xac dinh theo phuong phap d o n g i i n phu thudc ty sd can t u o n g irng £ nhU sau[6].
» . = ^ ' i » a p . = j i ; I " )
_2>i
trong dd. &,- — (12)
vdi. Tir la gia tri c^n. hi la ehieu day Idp dat t h i l i, H la t o n g c h i l u day ciia cae Idp dat
Giai phuong trinh ckn bang ciia he ket c l u - nen (9)xac dinh duqc c h u y i n Vj niit cLia cac phan tir va SLf dung cae quan he ciia PTHH tase tinh duqc ndi luc, bien dang va ii'ng s u i t trong moi phan tir. De gtai phUOng trinh (9)sir dung phuong p h i p tich phan trUc tiep Newmark k i t hop vdi phuong phap lap Newton-Raphson la h i l u qua han c a v e s u d o n gian, do 6n dinh va do chinh xac.
4. ThCr nghiem so Phuong phap ISGD:
" So lieu ban dau: Tinh toan chuyen vj bien do tac dung song c i t truyen 1 chieu theo phuong diing trong mdi trUcfng nhieu Idp cd chieu sSu H =50m va cac tham sd mdi tnidng theo bang 1 tren nen da gdc Gia toe nen tai khu vUc duqctra b i n g theotieuchuanTCVN 9386-2012 cd 3,=0,07g[1], pho phan irng dan hoi cho dat nen loai D.
BSng 1. Tham so moi trU6ng dat nhieu ISp fren nen da goc.
Win \6p ib-
LdpF Ldp lb Ldpl Ldp lb Lap 2 Ldp 2a Ldp 3 Ldp 4
day l6p (m)
2 3,5
mim
9,5 4,5 5,5 13T h a i n s o
Chieu
1 1 1 1 1 1 1 1
Khfii
(kN) 19/42 19,03 14,76 19,03 19,07 18,91 19,99 20,07
M d d u n E (kPa)
44.200 203.000 36.100 208.00 399,00 S18.DQQ 5S9.000 7S7,00
HesQ Poisson
0,4 0,4 0,4 0,4 0,4 0,4 0 4 0 4
D a m p i n g
0,3 0,3 0,3 0,3 0,3 0,3 0,3 0 3 Sirdung chuong trinh Soil Column Vibration -SCV2015 V1.0 duqc van toe, gia toe va c h u y i n v\ tuong ifng vdi t i i n g vi tri ciia theo do thi sau.
Hinh S.Bo Ihi quan he gia tot, van toe va chu/en vj theo chieu sau cat cot dat mi Cling til chuong trinh 50/2015.
* D a t hhi toan: Xet k i t eau cdng trinh ngam hlnh chif nhat kfch thuUc B/H = 20/6m, c h i l u day d a y / t u d n g ngan = 1/0,8m, E = 3,5E+07 kPa vah.E sd poisson c^a be tdng la 0,2dat t r o n g mdi trUdng nhieu Idp. Chuyen vi nen duocxae dinh phan tren (hlnh 5) d u o c d a t v a o m i l n bien d l xac dinh bien dang, ndi lUc eua ket cau M d hinh tinh ciia bai toan (hinh 2). Khi tfnh toan thifa nhan cac gia thiet sau:
- Vat lieu eiia ket cau lam viee trong giai doan dan hdi;
- Nen dat dUoc md hinh 11 dan - deo, cac tfnh chat cO hoc ciia nen thay ddi theo tifng Idp nhUng trong m d t ldp xem la khong ddi.
- Chuyen vi va bien dang tai diem bat k^ ciia he k i t cau - mdi trif6ng la nho. G i l t h i l t nay la chap nhan duqc vi ket cau edng trinh n g i m thifdng cd do cifng ldn hon n h i l u so vdi dd ciing ciia n l n dat.
- He ket eau va mdi trUdng lam viec trong d i l u kien bai toan pl
•m
I6p dat
Hinh 6 Mo hinh bin toan va rcfl rac hda PTHH
Hinh 7. Bieu do mfi men va luc cat
Hinh 8 Luc doc va bien dang cQa ham
Phuong phap dqng lUc hqc sd dung gian dd gia toe.
Xet cong trinh ngam n h u tren vdi gian dd gia tdc nen ed gia tdc dinh laag = 0,07g, n h u h i n h e a .
Dat bai toan' Xet tUOng taccOa ham - nen ehiu tac dung ddng dat.ti!
trong tac dung len he chfnh la sdng cat lan truyen trong mdi tru'dng dat mem anh hudng den cac ket cau cong tnnh ngam
Itinh 9 a) gia tocnen tai nen fla gSc va mat datb) diia ludl PTHH he
Hinh 10. Mo m e n M va li/c c3t Q cita hSm chiu tacflong ciia dfing flift.
i^*-V,fi^W'ii'M'^A«''*^^^
•^Wrt'/'^-vv^^-wt
lb 1 l-Luc doc H va bien dang ciia ham chiu tac dong ciia dang dat.
5. Ket luan
- Phuong phap lUc quan tfnh ia dang gl^i tich don g i l n eo the cung d p k i t q u i so b o ifng xir ciia k i t c l u n g i m chiu tac dung ddng dat n h u p h u o n g phap giai tfch tUdng minh ciia cac nha khoa hqc Wang v l Penzien (1993).
- Phuang phap ap dat chuyen v[ vao bien tinh toan co x l t den tuong tac k i t e l u vdi moi trUong nen.
- Phuong p h i p ddng lUc hqc sCrdyng gian do gia tdc nen la phSn tich theo ljch sir thOi gian. Phuong phap nay p h i n I n h day dit su tUOng tac dat ket c l u trong mot tran ddng dat. Trong d i l u kien khdng cd bang gia toe nen co the t^io g i l bang gia tde nen theo phUqng phap trinh bay 6 tren.
TAP LlEU THAM K H A O
[1]. Tieu chua'n Quoc gia 9386:2012 Thie't ke'cfing trinh chm flong dal, [2] Yao Xie, (2015), Seismic Response Analyses Method of Underground Structures in China, Intemational Forum on Energy, Environment Scienceand Materials.
[3]. Huaxin Zhao, Jurjie Zhao, Lihua Tan. Seismic Design of Underground Station and Case Study JJ], Building Structure. 2 0 1 3 ( S 1 ) : 1 1 1 4 - i n 8 .
[4]. ChopraA (2007), Dynamic of Structures TheoryAnd Application to Earthquake Engineering, Prentice Hall, New Jersey.
[5]. Das B,M. (1995), Principles of soil dynamics, PWS-KEfJT Publishing Company, USA.
[6i. Xiansheng, H., Zhihang, W. and Vimin, P. (1985), •The Effect of Underiying Bedrock Topography on Earthquake Ground Motion", Fifth International Conference on Numerica [7]. 1 Methods in Geomechanlcs, Uagoya
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