I KHOAHOC^ M S ! 3 ! E i ^ B
PHAN TICH ON DINH T 6 N G T H £ CUA DE C H A N SONG DA DO CO XET DEN AP L U C NlTdC KHE RONG TRONG NEN DAT
KS. Nguyen Tien Duong Phong Thi nghiem trong diem Qudc gia ve Dong luc hoc sdng bien PGS.TS T h i l u Q u a n g Tuin Trudng Dai hoc Thiiy loi
Tdm tat: Bdi bdo dua raphuangphdp tinh on dinh cd xet den su thay ddi dp luc khe rdng trong lap ddt nin gdy mdt on dinh tong the cua de chdn sdng dd dd mdi nghieng. Dieu do cho thdy su thay dii cdc dp luc khe rdng co vai tro quan trong, luong duang nhu cdc luc khdng cdt trong cdc lap ddt nen. trong on dinh ket cdu cua de chdn sdng Phuang phdp tinh todn duac dp dmg cho de chdn song ciia nhd mdy nhiet dien Viing Ang 1
Tir khoa: De chdn sdng mdi nghieng, Geoslope,Ap luc nude khe rdng. phdn lich dn dinh mdi doc Summary: The paper presents a method taking into account pore pressure variations in the subsoil in the overall slope stability analysis for rubble mound breakwaters. It is shown that the pore pressure variation plays an important role, comparable to the shear strength of the subsoil, in the overall stability of the slruciure. A case study is also present for the breakwater of Vung Ang I thermal power plant
Keywords: Rubble mound breakwater, Geo-Slope, Pore pressure variations. Slope stability analysis
I. DAT VAN DE
Vai trd cua de chan sdng la giam sdng tao khu nude tinh cho be cang, ngan chan sir bdi ling bun cat trong be cang va tao ludng giao thdng thuan tien giup cac phugng tien giao thdng thOy di Iai de dang. Cdng viec thiit k l de chin sdng phai xac dinh dugc vi tri tuyIn de hgp ly tren mat bang, thiit ke dugc cac thdng sd hinh hoc cua de nhu: cao trinh thiit k l , b l rgng thiet ke, he sd mai, lua chgn dugc cac loai c i u kien pha sdng (da dd hay eae khii be tdng di hinh nhu tetrapod, cube, dolos, rakuna,...) d l vira dam bao vai trd cua de vira tilt kiem chi phi xay dimg cdng trinh. Do dac diim cdng hinh de chan sdng hay phai bd tri each xa bd nen de thudng bi dat tren nen dat yiu. Do dd viec tinh toan dn dinh ciia de chin sdng la
Ngirdi phan bien: TS. Phan Trirong Giang Ngay nhan bai: 19/8/2014
Ngay thdng qua phan bien: 17/9/2014 Ngay duyet dang: 13/10/2014
cdng viee quan trgng. Hau het de chan sdng thudng duge thiit k l theo hinh thilc de mai nghieng, cac nghien ciru tinh toan dn dinh de mai nghieng chua de cap tdi anh hudng cua ap lire nude khe rong trong cac lop dit nIn dugc sinh ra do sdng va thtiy trieu gay m i t dn dinh mai de phia biin cua de chin sdng mai nghieng. Trong bai bao gidi thieu mdt phuong phap tiep can mdi trong viec tinh loan I n dinh cd de cap tdi ap lire tren va ap dung tinh toan tren thuc t l cho cdng trinh de chin sdng nha may nhiet dien Vung Ang 1.
II. D O I T i r O N G V A P H l / O N G PHAP NGHIEN c i r u
Phan tich dn dinh mai nghieng cua cac cdng trinh cd sir dung vat lieu d i p ndi chung hay de chan sdng ndi rieng thdng thudng hay ap dung phuong phap cua Felleniuos, Bishop vdi gia dinh mat trugt la mat tru trdn xoay quanh mot true nam ngang hoac phucmg phap cua Janbu, Nonveiller vdi gia dinh mat trugt g l y khiic.
TAP CHI KHOA HOC VA CONG NGHE T H O Y LOI Sfi 23 - 2014
KHOA HOC B B 5 I M ! B 5 M i
Cac phuong phap deu dya tren nguyen tic chia kbdi trugt thanh cac phan manh cd be day du nhd de phan tich tinh toan. Phan tich dn dinh dai ban trang thai ung suat hieu qua vdi 2 yeu td chinh dugc quan tam lagdc ma sat trong <p va luc dinh c. Viec tinh toan be sd an toan cua mai phia bien ciia de chan sdng dugc dua tren cac yeu td: mat cat dai dien cua de, ngoai luc tac dung, ap lyc nude khe rdng cua dat nen, chi tieu co ly cua vat lieu dap de va nIn dit.
So dd tinh cho 1 phan manh nhu hinh 1
Hinh 1. Cdc luc tdc dung ddi vdi 1 phdn manh
• Trpng lugng ban than W - Phan luc R len cung ab
- Phan luc tu 2 mat trugt dung ac va bd. Day la ndi lyc ciia khoi dat trong mat trupt dang xet Cac thanh phan xem xet md men ddi vdi tam trugt 0 ;
- Md men gay trugt: md men ddng lyc tu trpng lugng ban than W
- Md men khang trupt: md men do cac lyc Rn, H„,Hn+,,Vn.,vaV„ '
Xet tong hgp cac md men ddi vdi cung trong ab, cac md men do cac lyc tuong tac giiia cac lat chia se tu triet tieu. Tlieo gia thiet ciia Fellenius chi cdn Iai mot luc duy nhit dd la trpng lugng ban than W va phan luc R. Phan tich trpng lugng W, phan luc R tbeo phuong tiep tuyen vdi mat ab thanh lyc Wj, Rrva theo phuong phap tuyIn vdi mat ab thanh lyc Wn, Rn-
Md men khang trugt eye dai la thanh phin lyc
tiep tuyen ciia R tbeo dinb luat Coulomb cd dugc Rn = c a b + N.tg tp. Tdng md men ciia tat ca cac phan manh trugt la Sf=iR(Ci_.ab + N.tg(pj)
Md men gay trugt bao gdm:
- Thanh phan tiep tuyen ciia trpng lugng l i l . R . W j
Md men khang trugt bao gdm:
- Thanh phan tiep tuyen ciia lyc S f = : R ( C i , a b - l - N . t g < p O
He sd dn dinb Fs dugc tinh theo cdng thuc:
P _ rLR;C:,ab-N,tg>Pi}_C:3b-fN.Tg(f>i
Van giu nguyen gia thiet ciia Fellenius, nay xet them ap lyc U tir ben trong cac Idp dat nen tac ddng len kbdi trugt. Lyc tac ddng do ap luc U khdng phai la ap lyc nude thiiy tinh trudc mai de phia bien ma lyc U dugc hinh thanh do sy thay ddi ciia muc nude trudc mai de phia bien'^'l
Hinh 2. Ap luc nude Id rdng dudi ddt nen phu thugc vdo qud trinh nude rut ciia mice nude bien Gia thiet cd 1 phan td cd kich thudc dx, dy,l va bi anb hudng bdi thuy trieu
Xet phan td trong ddng tham tbeo phuong diing trong phuong trinh tham ciia Darcy:
_ k du
(II-2)
Tham khao tai lieu: JuHen De Rouck, Robert A.
Grace; "Surface wave heights from pressure records", "overall slope stability analysis of rubble mound breakwaters".
TAP CHf KHOA HOC VA C O N G N G H ^ T H O Y LOl S6 23 -
1 KHOAHOC ^ESSSSi^M
w: Van t i c ddng chay tbeo phuong z u: Ap luc nude Id rdng
k: He sd tham cua dat
pw: Kbdi lugng rieng ciia nude bien De lap phuong trinh lien tuc, xet phan td trong vdi cac dieu kien bien cd ke den cac yeu to sau:
-Neu muc nude bien ba tir myc nude trieu cao xudng myc nude trieu thap, ap luc nude Id rdng giam dl; the tich 16 rong trong dat tang len, cac phan tu nude nit ra kbdi dat va sinh ra ap lyc.
- Cling liic dd ling suat hieu qua giam (giam ve phuong ngang va phuong diing): dat gian ra va nude hi hut vao
Phuong trinh lien tuc:
£ ^ = _ ( ^ + JL)£.
(11-3)Eeod: Mo dun dan bdi ciia dat n: Dp rdng ciia dat Kvv: md dun nen cua nude bien
Gia thiet tat ca cac lop dat nim dudi myc nude bien deu d trang thai bao hda nude Ket hop phuong trinh ciia Darcy va phuong trinh lien tuc din tdi phuong trlnb ap luc phia dudi nude bien.
oz- k V E , ^ ^ OX ' Mdt each tuong ty phucmg trinh chung ciia
ddng chay trong long dat do tac ddng cua song cd the dugc viet nhu sau;
Do gia tri — rat nhd nen cd the bd qua
i:<- dz- k VE„i/ dl
c ' 1 . . ^ . ^i . Pw§ i t \du So sanh gia tn T-^ va — - 1 — trong
i:<- k \ZgoiJ 3t ^ trudng hgp sdng trung binh, ddi vdi nIn dit set va dat bim gia tri T-Z nhd hon nhieu
ox
1 - — I — nen bieu thiic duac viet Iai thanh:
i i _ Pwg/ 1 \dti oz= k ^n,^J ai
Hai phuong trinh (5) va (8) gidng nhau Dieu kien bien dl giai 2 phuong trinh tren:
a, Tai muc nude biin (z=0) u(0,t) = u o c o s ( — - — )
Tai 1 diem cd dinh xem xet ta liy x = 0
'7t
u(0,t) = UoCOsf—j Ddi vdi trilu: uo= Pw.g.Hse + — l - r (11-4)
Do nen cua cdt dat dugc kl din thdng qua ty ^ o ' ™ sdng: uo = P..,.g H
(11-10) (11-11) (11-12)
Do nen cua nude bien thdng qua ty sd -7- So sanh ve do Idn giiia 2 he sd tren cho ea dit eat lan dat set thiy ring ^ cd gia tri nhd hon nhieu lan ^ , vi vay ta cd thi bd qua ~ . phuang trinh tren chi cdn
H: Chieu cao sdng L: Chieu dai sdng d: Do sau mirc nude n: He sd dieu chinh Grace b, Tai do sau vd han (Z=M)
u(z,t) = uo . e - ' ^ e o s ( i ^ -|- i | ^ _ ^^^ (jj.jjj
M TAP CHl KHOA HOC VA CONG NGHC T H l l Y LOI 5l3 23 - 2014
KH()AH(i(: • I III III 1,1 •
Trong d6:A= ' - J ^ ^ ^ I H (11-14) T: Chu ky sdng
L: Chieu dai sdng k: He sd tham ciia dat Eeod: Md dun dan hdl ciia dat
Bang nhieu bien phap do dac su thay ddi ap luc trong cac Idp dat nen dudi tac ddng ciia thiiy trieu va sdng dugc the bien trong dd thi binh 3.
Dudng cong (1) cd gia tri x = 0, t = T/2 va A = 0,3, trong khi dudng cong (2) la gia tri tdi ban cita dudng ap luc. Xap xi dudng cong (1) cd the dugc xap xi bang cac dudng thang AB. Khoang each OB dugc gpi la "dp sau anh hudng". Gia tri dp sau anh hudng nay cd y ngbTa Idn trong viec xem xet ap luc nude khe rdng trong dat nen doi vdi tinh toan dn dinb mai ddc phia bien eiia de chan sdng mai nghieng
Tnrdng hop 1: Tinh toan dn dinb mai de phia bien ling vdi myc nude thiet ke khdng ke den ap lyc nude khe rong u ben trong cac Idp dat nen.
Trirtrag hgp 2: Tinh toan dn dinh mai de phia biin ling vdi muc nude thap nhat cd ke den ap lyc nude khe rdng u ben trong cac Idp dat nen.
Trong trudng hgp nay, tinh toan dn dinh dua tren td hgp tai trgng co ban co xet den sir anh hudng ciia ap luc khe rdng u cua cac lop dat nen dudi tac ddng ciia sdng bien theo ly thuyet ciia DE ROUCK:
- Xet su anh hudng ciia myc nude do sdng tac ddng trong dieu kien myc nude nhd nhat MN min = +0.5 m, chieu cao sdng H = 3,5m - Xet anh hudng ap luc U tdi cac Idp dat dudi nen do tac dpng cua sdng theo cong thiic cua DE ROUCK
Cac tham sd thiet ke ciia cdng trinh
Hinh 3. Su thay ddi dp luc nude 16 rdng ben trong ddt nen do thuy trieu vd sdng ffl. KEF QUA NGHIEN CUtJ VATHAO LUAN Vdi phuong phap luan da trinh bay phan tich d tren, ap dung tinh toan cho de chan sdng cua nha may nhiet dien Vung Ang I. De lam rd vai trd ciia ap lyc nude khe rdng ben trong Idp dat nIn gay mit dn dinh mai de phia bien, ta se tinh toan dn dinb mai de phia bien ciia cdng trinh trong 2 trudng hgp:
Mac nude Min (m)
+0,5
Muc nirdc thiet ke
(m) +2,13
Chieu cao song Hs
(m) 3,5
Cao trinh dinh de
(m) +6,0
Dya vao "Bao cao dia chat cdng trinh" cua khu vyc nghien ciiu, ta cd dugc chi tieu co ly ciia cac Idp dat tai hd khoan CW-38:
Lop 3; Cdt pha xdm den, xdm trdng, xdm ghi, xdm vdng, deo.
Ldp 3 phan bd cue bp, chi xuat bien trong hd khoan DC7, DCS, DCU va DC 15, nim dudi Idp 3a tai chieu sau tir 2.2m (DC15) den 15.3m (DCS). Mat ldp tai cao do -4.0m din -9.3m. B I day cua ldp tuong ddi dn dinh trung binh 3.0m. Thanh phan cbii yeu ciia Idp la Cat pha xam den, xam trang, xam ghi, xam vang, trang thai deo. Trong ldp nay da lay va tien hanh thi nghiem 09 mau, cac chi tieu co ly dugc tdng hop tai bang 1:
Ldp 5b.- Set pha mdu xdm trdng, xdm ghi, xdm xanh, ddi chd ndu vdng, Idn it sdi san thgch anh, trgng thdi deo mem
TAP CH[ KHOA HOC VA C O N G N G H E T H O Y LOI S 6 23 - 2014 65
'KHOAHOC " ^ E S B I S i l M
Ldp 5b chu yiu nSm dudi ldp 4 mdt phan nhd nim dudi ldp 3 a hoac nim ngay dudi ldp 3. Ldp nay bit gap d do sau 7.3m den 16.0m.
Mat ldp gap tai cao dg -4.3 -:- -10.5m, day ldp kit thiic tai cao do -7.5 -:- -12.8m. B I day cua ldp thay ddi tir 1.4m din 5.3m, trung binh 3.4m. Thanh phin chu yiu cua ldp la Set pha mau xam tring, xam ghi, xam xanh, ddi chd nau vang, lan it sdi san thach anh, trang thai deo mem.
Ldp 5: Set pha mdu xdm trdng, xdm ghi, xdm xanh, doi chd ndu vdng, Idn it sdi sgn thgch anh, trgng thdi deo mem
Ldp 5 bit gap d do sau 1.1m den 9.6m. Mat ldp gap tai cao dg -2.50 -:- -9.3m, day ldp kit
thiic tai cao dd -4.40 -:~ 12.6m. Bl day ciia ldp thay ddi tit 1.3m din 4.9m, ttung bmh 3.1ni.
Thanh phin chu yiu cua ldp la set pha mau xam tring, xam ghi, xam xanh, ddi chd nau vang, lin it sdi sgn thach anh, trang thai deo mem.
Ldp 8a: Dd riolit phong hod manh Hit thdnh set pha Idn ddm sdi, sgn mdu xdm vdng, xdm trdng, trgng thdi cung.
Ldp 8a nim dudi ldp 5 hoac ldp 3, tai do sSu 7.1m din 9.2m. Cao dd mat ldp thay doi tir - 8.5m-;- -11.7m. B I day cua ldp thay ddi tit 1.9m din 2.1m, trung binh 2.0m. Thanh phSn chu yiu cua ldp la da riolit phong hoa manh liet thanh thanh set pha lan dam sdi, san mau xam vang, xam triing, trang thai cung.
Biing 1. Chi tieu cff ly ciia cac Idp dat STT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Cac chi tieu Dd am tu nhien Giai ban chay Gidi ban deo Chi sd deo Do set
Khoi lugng the tich tir nhien Khoi lugng the tich khd Khoi lugng rieng He sd rdng He sd Id rdng Do bao hoa Gde ma sat trong Luc dinh ket He sd nen lun Ap luc tien cd ket He sd cd ket Ap lire tinh toan quy udc Md dun tdng bien dang
Ky hieu W Wd, Wd Id Is 7w 7C A eo n G
<P C ai.2 Po C, Ro Eo
Dffn vi
%
%
%
% -
g/cm' g/cm g/em^
-
%
%
do kG/cm^
cm^/kG kO/cm^
xlQ-^
cm^/sec kG/em^
kOkn?
Ldp 3 18.6 24.82 15.4 9.42 0.36 1.18 1.66 2.69 0.625 38.12 82.24
for
0.109 0.024 0.58 2.45 0.95 100
Ldp 5b 25.3 31.03 19.08 11.95 0.52 1.26 1.12 1.71 0.739 41.99 92.77 8°19' 0.118 0.03 0.60 1.56 1.1 140
Ldp 5 21.8 28.16 16.67 11.49 0.45 1.60 1.34 2.71 0.661 39.40 89.48 7°21' 0.111 0.031 0.649 1.648 1.19
126 Ldp 8
18.67 32.56 17.78 14.78 -0.01 2.00 1.70 2.68 0.595 37.29 80.58 19°56' 0.203 0.026 2.28 210
66 TAP CHl KHOA HOC VA CONG N G H E T H O Y LOI Sl3 23 - 2014
KHOA HOC
mim
Hinh 4. Mat cdt dgi dien cua de chdn sdng Theo nhu phucmg phap nghien cuu da trinh bay,
ta cd dugc phuong trinh xac dinb mdi quan he '" -^i k=c«rf^ ^ giua ap lyc du khe rdng u(z,t) va dg sSu z. j . ^^u ky sdng u(z,t) = uo.e"'^cos(Y^ + ^ ~ Az) (III-l) L: Chiiu dai sdng
^ , . ^ •> ^ -• jj ^ ^ k: He sd tham cua dat Cma ca 2 ve cho Uo ta dugc
uz fi A-. -Tz\ :rrt Eeod: Md dun dan bdi cua dat
— - = e " ' ^ ' . c o s ( ^ + — - A z ) (m-2)
^0 L T j^gj q ^ ^jjj^ jQ^ ^gQ ^y thuyet Grace xac Trong dd theo cdng thiic (11-14): dinh dp sau anb budng^"'
z U(z,t)/Uo
^(-Az)
0,00 1,00 1,00
1,00 0,75 0,78
2,00 0,53 0,61
3,00 0,35 0,47
4,00 0,20 0,37
5,00 0,09 0,29
6,00 0,02 0,22
7,00 -0,03 0.17
8,00 -0,06 0,14
9,00 -0,07 0,11
10,00 -0,07 0,08
•0 2 0 3
Hinh 5. Bieu dd quan he dp luc du khe rdng vd do sdu
Ap lyc du do thiiy trieu tac ddng den mat dn dinb ciia cdng trinh dien ra ttong thdi gian dai. Trong tmdng hgp nay ta chi xet tdi tai tong tac ddng do song bien. Tbeo cdng tbiic (II-12) ta xac dinb dugc
Tham khao tai lieu: Nguyin Tien Duong, luan vSn thgc sy "Danh gia hieu qua cua vai dia k j thuat gia c6 nSn de chSn song co xet toi anh huong cCia tai trong song biin, ap dung cho de chan song nha may nhiet dien vung ang 1"
P..-.E.H 1.025-9.8,2.2
Un = ' -re = r2Tr= 8,338 (Kpa) Tai khu vuc nghien cuu ta cd gia tri - ^ — = 0,063 (trich suat gia tri tir ket qua truyen sdng). Tra tbeo ket qua thyc nghiem ta cd dugcn= 1,273.
- Tai vi tri z ^ 0
U(z.t)= ( ^ ) - U o = 1.8,338 = 8,338 (Kpa) Tai vi tri z = 5
U,^,)- ( ^ ) . U o = 0,1.8,338 = 0,8338 (Kpa)
V U(j ^
Quy ddi Im = 10 Kpa ta cd dugc cac gia triap luc quy ddi lan lugt la U(z = o) = 0,8 (m) va U(z=
Si = 0,08 ^ 0,1 (m) Ket qua tinh toan:
TAP CHf KHOA HOC VA C O N G NGHt T H O Y LOI SO 23 - 2014 67
KHOAHOC " ^ E S B I B i I ^
Ket qud tinh todn truong hgp 1-Kfi = 1,25 Ket qud tinh todn trudng hgp 2~Kfs- 1,07
IV. KET LUAN
Viec tinh toan tuong tac giiia sdng va thiiy trieu doi vdi on dinh ciia cdng trinh doi bdi phai CO nhirng nghien cuu chuyen sau de mo phdng dugc het cac hien tugng xay ra khi song va thuy trieu tuong tac vdi cong trinh nbu: qua trinh song riit, song leo irng vdi cac thdi diem myc nude trieu khac nhau. Do ban che ve sd lieu va cac dieu kien bien tinh toan nen trong
bai bao tren cbi de cap viec tinh toan trong thdi diem sdng nit khi bung sdng tiep xiic vdi cdng trinh img vdi tbdi diem myc nude trieu thap. Ket qua tinh toan cho thay cac ap lire nude khe rdng ben trong cac ldp dat nen gay anh hudng mat dn dinh cho cdng trinh, do do khuyen nghi trong cac tinh toan dn dinh dii vdi de chan sdng mai nghieng can phai tinh toan ddi vdi trudng hgp nay.
68 TAP CHf KHOA HOC VA C O N G N G H G THUY LOl S 6 23 - 2014
