PHU'QNG PHAP MO PHONG TREN MO HJNH S6 PHA SONG BANG KET QUA NGHIEN CLFU XAC DINH MU'C DO GIAM SONG CUA CONG

P H A N I - THUY Ll/C, SONG BIEN vA PHONG CHONG LLJT BAO... 219

KET QUA NGHIEN CLFU XAC DINH MU'C DO GIAM SONG CUA CONG

T R I N H G I A M

PHA SONG BANG PHU'QNG PHAP MO PHONG TREN MO HJNH S6

TS. Nguyin Khdc Nghia"' KS. Doan Tiin Hd"'

Dat vin d§

Hien nay nhu cau xay dyng cac cong trinh chu dpng pha song gay boi tren bai truac de bien mham on dinh bai va giam song tac dpng len he thong de bien la rat lan, nhat la tai cac vimg trpng diem sat la bai va de bien. Viee sir dung cong cu mo hinh so de xem xet nghien ciiu danh gia anh huong ciia cac cong trinh pha song gay boi bao ve bai bien nham phuc vu cong tac quy hoach xay dyng cac he thong cong trinh pha song gay boi tren bai bien co y nghTa thuc tien rat cao hien nay. Dp cao song dupc sir dung de tinh toan he so suy giam song R la he so xac dinh bang thucmg cua hieu dp cao song

, . , . ^ . , , X , » . . . . „ _ 1 ^ - 5 /

toi vol do cao cua song truyen qua va do cao song toi: R — i Hsi

Trong do: Hsi - chieu cao song toi; Hst - chieu cao song sau cong trinh tren bai.

I. Cc sa toan hoc cua mo hinh tinh toan lan truyen song vung ven bd" PMS

Ll. MIKE 21 PMS - khd nang vd phgm vi ung dung

MIKE 21 PMS la mo hinh tinh toan song khiic xa va nhieu xa song tuyen tinh dya tren xip xi parabolic ciia phuang trinh dp doc thoai eliptic. Mo hinh tinh toan cac hieu irng khiic xa va can song do dp sau nuac bien dpng, nhieu xa dpc theo huang vuong goc vai hucmg lan truyen song va tieu tan nang lugng do ma sat day va song vo.

MIKE 21 PMS sir dung mot s6 dang xap xi parabolic tir dang xap xi dan gian ap dung cho cac goc nho din cac xip xi phirc tap doi vdi cac goc song toi Ion (+/- 60").

Phuang trinh dang parabolic dugc giai sir dung so do sai phan hiru han Crank - Nicholson. Cac s6 lieu diu ra cua mo hinh la cac tham so song nhu dp cao song quan phuang, chu ky dinh ph6 va huong song trung binh, ngoai ra con co the xac dinh dugc irng suit song va cao dp be mat nuoc tire thai.

Mo hinh MIKE 21 PMS co thi ap dung de nghien ciru tinh toan truang song tac dpng tai viing bo biln ma va tinh toan truang song tai viing ven bo vai cac dang cong trinh nhu dap dinh, de pha song) khi phan xa song tir cong trinh co the bo qua va hien tugng nhieu xa chiim vai tro chii dao tren huong lan truyen song.

' Phong Thi nghiem Trgng i\km Qu6c gia vl dong lire song bi6n - Vien KHTLVN

1.2. Cdc gid thiit vd hi phwffng trinh cff bdn

Mo hinh MIKE 21 PMS dya tren xap xi parabolic cua phuang trinh do doc thoai eliptic la he phuang trinh co ban de mo ta cac hien tugng khiic xa, nhieu xa va phan xa ciia song tren day bien thoai. He phuang trinh dugc Berkhoff xay dyng tir nam 1972.

He phuang trinh do doc thoai eliptic co the viet duoi dang:

V . (C Cg V(()) + (k^ C Cg + icoW) (j) = 0 (1) trong do:

V - toan tir gradient hai chieu, {d/dx, dld\);

C(x, y) - van toc pha;

Cg(x, y) - van toc nhom song;

(j) (x, y) - the van toc trung binh cua be mat ty do, lien he vai the van toc if bang bieu thirc sau:

^(.\;y. z, t) = —(f)(x, X) e (2) CO Cosh kd

z - cao dp muc nuac dugc xac dinh tir myc nuac biln trung binh theo huang len tren;

d - dp sau;

k - so song = 27t / L;

W - thanh phan tieu tan nang lugng, W = E diss / E;

Ediss - tic dp tieu tan nang lugng trung binh tren mpt dan vi thai gian va tren mpt don vi dien tich ;

E - nang lugng trung binh tren mpt dan vi dien tich;

G) - tan so vong = 27:f;

L - buac song;

f - tan so.

Cao dp bl mat ty do r) co the vilt duoi dang nhu sau theo Dean & Dalrymple, 1984:

/ cd)' '?= — r -

g c/l.^^

!] = t/)f\,yje''"'''-' (3) D6i vai song tien phang, bl mat thi ty do co thi vilt duoi dang:

<l) = A*(x,y)e''^ (4)

PHAN I - THUY Lire, SONG BIEN vA PHONG CHONG LUT BAO... 221

trong do:

4 ' = f k cos l9 dx + f' k sin 61 dy (5) vai 0 la goc giiia hucmg song lan truyen va true x, ham pha T co thi vilt duoi dang:

^ = f k dx (6) Phuang trinh (5.1) co the ma rpng nhu sau:

(C Cg (j),)x + (C Cg (j)y)y + (k^ C Cg + icoW) (() = 0 (7) trong do cac chi so duoi x, y la dao ham theo cac huang x va y.

Sir dung phuang trinh (4) la cac gradient thanh phan c6 the viet duoi dang:

<t)x = (ikA* + A*x) e '* (8)

CCg (j)x = (ico Cg A ' + C Cg A\) e ''^ (9)

(CCg(t)x)x = [ik(ico Cg A* + C Cg A*x) +

+ ico Cg A \ + icoA*(Cg)x + (CCg A\\]e ''^ (10) Dai lugng cuoi ciing trong phucmg trinh (10), (CCg A x)x the hien anh huong cua hien tugng phan xa va nhiiu xa dpc theo huang x dugc bo qua trong xap xi parabol.

do do:

(CCg(()x)x = [ { - k c o C g + ico(Cg)x} A* + 2 i c o C g A \ ] e''^ (11) Cuoi cimg, sir dung (4)

(CCg(t)y)y s ( C C g A * y ) e ' ' ^ (12) Thay the phuang trinh (11) va (12) vao phuang trinh (7) se co:

A : - -^— f cc, .4: K - -i '-%^+A^=0 (13) 2cc,c, ^Cs -C,

Kirby (1986) m a rpng phuang trinh cho truang hgp song lan truyen tren goc Ion so vai huang chinh cua song:

A. + U ko - Pi !^->A + -i—f CV A- --^^' CC, Ar A 2C, COC,

a^ "

/ C Q J v A , - — r - - i = (^ (14) COC, ^ " -C

Day chinh la he phuang trinh co ban cua mo hinh MIKE 21 PMS.

He phuang trinh nay dugc giai bang so do so Crank - Nicholson doi voi he phuang trinh sai phan parabolic, he phuang trinh dai so ba duang cheo dugc giai bang thuat toan quet kep.

II. K4t qua tmh toan tru'd'ng song va cong trinh pha song gay boi ILL Cdc so lieu ddu vdo

1. So lieu song nw&c sdu

S6 lieu song nuac sau co vai tro quan trgng quyet dinh doi vai cac mo hinh tinh toan lan truyin song. Tinh Nam Dinh ciing nhu toan bg mien Bac Viet Nam nam trong viing khi hau can nhiet dai dac trung bai hai miia gio: gio miia dong bac trong miia dong va gio miia tay nam trong miia he, khu vyc Hai Hau - Nam Dinh co duang ba theo huang Dong bic - Tay nam triing voi huang lan truyen chinh ciia song Dong bae.

D6i vai khu vyc nghien ciiu theo cac ket qua thong ke tinh toan song trong bao va nuac dang trong cac truang hgp bao cap 9 va cap 12 do bg vao khu vyc theo huang vuong goc vai duang ba ket hgp vai cac truong hgp muc nuoc thuy trieu trung binh va cyc dai dugc the hien tren bang 1.

Bdng 1. Cdc thong so song vd muc nuac duoc dua vdo tinh todn

Truong hop tlnh

toan 1 II III IV

Muc nuccc thiiy trieu [m]

1.2 1.2 2.0 2.0

Song Chi4u cao [m]

2.01 2.7 2.01

2.7

Chu ky [s]

6.7 10 6.7 10.0

Muc nuoc dang do bao [m]

1.5 2.0 1.5 2.0

Muc nuoc tong cpng [m]

2.7 3.2 3.5 4.0

2. So lieu trw&ng dp sdu

De thyc hien cac tinh toan ciia mo hinh PMS da sir dung cac ban do khu vyc ven bien tir nhieu nguon khac nhau bao gom:

+ Binh do do dac ven bien Hai Hau- Nam Dinh giai doan 2006-2008 ciia Trung tam Dpng lyc Cira song ven bien va hai dao, ti le 1: 25.000.

+ Hai do do Hai quan nhan dan Viet Nam xuit ban nam 2005, ti le 1:100.000.

+ Ban d6 UTM ti le 1: 50000.

+ So do AUTOCAD the hien vi tri cac phuang an cong trinh chinh tri.

Truang dp sau va cac phuang an bo tri eong trinh cua hai khu vyc Hai Hau Nam Dinh dugc the hien tren hinh 1 va 2.

Cong trinh ngan cat, giam song chii T dugc thilt kl triin khai tai Hai Hau vai mpt s6 dac diem cu the nhu sau: Vi tri tuyen de: Ke chii T c6 phin canh dugc bo tri bam theo duang dong mirc -2.0 nhu trong phan quy hoach da dl cap. Do do, cao trinh chan canh ke la -2.0m. Cao trinh dinh phan canh: chgn Zj = +3.5 m. Phin than: cao trinh glc ke md han +2.0, cao trinh mui ke la +1.7. Chiiu dai binh quan cac mo la 350 m.

Tai khu vyc nghien ciiu ven biln Hai Hau 02 phuang an quy hoach cong trinh giam song gay b6i tren bai dugc dua vao lya chpn thong qua mo phong hieu qua giam song bang mo hinh so:

P H A N I - THLJY LUC, SONG BIEN v A PHONG CHONG LUT BAO... 223

- Phuang an quy hoach I gom 8 ke chii T va 3 de ngam co ehieu dai lan lugt doi vai cac de tir N l tai N 3 : 501 m, 501 m, va 538 m, khoang ha giua 2 dau de khu vyc nay dugc lay la 145 m.

- Phuang an quy hoach II gIm 7 ke chii T va 2 de ngim N l va N2 co chieu dai nhu nhau la 501 m.

Tir cac ban do va ban ve thiet ke da xay dyng cac truang dp sau tren luai tinh 5 m X 5 m phuc vu mo hinh PMS tinh toan truang song bao lan truyen tai cac khu vuc Hai Hau (Hinh 3 la thi du the hien cho phuang an quy hoach I).

TOA f j 6 DI^M CHAN CflNG T R I N H ciy DIEU KH^G CHfxt 1>U C ^ TO OO)

BigCitr s4noDi

M7(5B 6iCM<4 «Ngim

Xirirt 1\W,

..SKU.

N3

..mui. ^{mini Mild I D M}

Hinh 1. Bdn do khu vwc Hdi Hdu Nam Dinh v&i phwffng dn cong trinh bdi I

-l-XX_ x-x _~L

Hmh 2. Bdn do khu vwc Hdi Hdu Nam Dinh v&i phwffng dn II eong trinh bdi

Bathymetry

0 IM 2M 3..>0 4M !-:0

Hinh 3. Trw&ng dp sdu trin lw&i tinh 5 m x5m khu vwc Hdi Hgu Nam Dmh v&i phwffng dn cong trinh bdo vi b& I gdm 08 ke ciiii- T vd 03 de ngdm

II.2. Cdc bw&c thwc hien tinh todn

Vcfi cac so lieu dau vao da dugc chuin bi tai cac muc tren, mo hinh PMS dugc van hanh vai cac buoc khai bao lan lugt nhu sau:

PHAN I - THUY LLJC, SONG BIEN vA PHONG CHONG LtJT BAO... 225

/. Cdc tham so cff bdn

- Dia hinh: dang mo phong chuin PMS hai chieu (Normal PMS); Ten file so lieu dia hinh.

- Vi tri toa do dia ly cua khu vyc tinh toan mo phong: tpa dp goc, huong quay ciia luai, gia tri the hien khu vyc dat lien.

- Dang tinh toan theo thai gian: khong thay doi theo thoi gian (Stationary); thai diem bat dau tinh toan.

2. Cdc dieu kien Men

- Bien ngoai khai: song khong deu lan truyen theo cac huang (Irregular directional); tham so song: chu ky dinh, dp cao song, huang lan truyen.

- Bien ben: doi xung (Symmetrical).

3. Cdc tham so mo phong

- Cao dp myc nude: dang gia tri Idiong doi (Constant value); gia tri cao dp myc nuac.

- Cac tham so thuat toan: cac he so PMS, he so lpc.

- Cac tham so tieu tan nang lugng do day, dang he so, lya chpn kieu gia tri.

- Tham s6 tieu tan nang lugng song do song do.

4. Kit qud

- Xac dinh ten file chira ket qua tinh.

- Lya chpn cac tham s6 luu giir: Dp cao, chu ky, hucmg; Cao dp myc nuac; Cac thanh phan vecto, ii-ng suat phat xa.

II.3. Kit qud tinh todn cho khu vwc cong trinh tgi Hdi Hdu

Da tinh toan cho khu vyc cong trinh tai Hai Hau vai cac ket qua sau:

- Truang hgp song bao cip 9 vai dp cao song 2.01 m, chu ky 6.7 s lan truyen vao khu vyc Hai Hau tren nin muc nuac (Trilu + ND) 2.7 m va 3.5 m la vai phuang an cong trinh bao ve ba I va II.

- Truong hgp song bao cip 12 vai dp cao s6ng 2.7 m, chu ky 10 s lan truyen vao khu vyc Hai Hau tren nin myc nuoc (Trilu + ND) 2.7 m va 3.5 m vai phuang an cong trinh bao ve ba ve ba I va II.

Cac hinh tir 4(a, b) din 7 (a, b) minh hpa kit qua tinh cho PAI. De tien so sanh cac hinh 9 va 10 thi hien truong song tinh toan cac cap bao 9 va cip 12 lan truyen tren nen 04 gia tri myc nuac cyc tri vao khu vyc Hai Hau khi khong co cong trinh.

Truang hgp song bao cip 9 vai dp cao song 2.01 m, chu ky 6.7 s lan truyen vao khu vyc Hai Hau tren nin myc nuoc 2.7 m la t l hop cua myc nuac trilu trung binh 1.2 m kit hgp vai nuoc dang do bao 1.5 m voi phuang an cong trinh bao ve bo I dugc thi hien tren hinh 4 (a, b).

Hrms [m]

Hrms [m]

^ H Above

^ ^ 1 n - 1 1 1.55 - 1 1 1 .5 - 1 1 1.35- 1 1 1 ? - 1 1 1 05 - r 1 0 9 - K y 0 . 7 5 -

I M 0.6- I H 0.45-

^ H 0.3-

• • 0.15-

^ H

^ H -0.15- I H Below

1.95 1.95 1,8 1,65 1,5 1,35 1,2 1,05 0,9 0,75 0,6 0,45 0.3 0,15 0 -0,15 1 1 Undefined Value 100 200 300 400 500

(Grid spacing 5 meter)

Hinh 4a. Trw&ng song tinh todn bdo edp 9 v&i dp cao song 2.01 m, chu ky 6.7s lan truyin tren nin mwc nw&c tdng hffp 2.7m vdo khu vwc Hai Hgu

v&i phwffng dn cong trinh I

PHAN I - THUY Lt/C, SONG BIEN vA PHONG CHONG LUT BAO... 227

Hrms [m]

Hfms

^M

^ B 1 1 1 1 1 1 1 1 1 1 i 1 ffSSl

^ H

^M

^M WtM

• •

• •

1 ( Im]

Above 1,8- 1.65- 1,5.

\35- 1,2- 1,05- 0 , 9 - 0,75- 0,6- 0,45- 0 , 3 - 0,15- 0 - -0 15- Belovtf

1,95 1 95

1,8 1,65 1 5 1,35 1 2 1 05 0 9 0,75 0 6 0 4 5 0,3 0 15

0 -0 15 Undefined Value 400 450

(Grid spacing 5 meter)

Hinh 4b. Trw&ng song tinh todn bdo cdp 9 v&i dp cao song 2.01 m, chu ky 6.7 s lan truyin tren nin mwc nw&c tdng hffp 2.7 m vdo khu vifc Hdi Hdu v&i phwffng dn cong trinh I (Khu vwc trich xudt s6 lieu kl; D4, di ngam Nl, de ngdm N2, ke D5)

Truang hgp song bao cap 9 vai dp cao song 2.01 m, chu ky 6.7 s lan truyen vao khu vyc Hai Hau tren nen myc nuac 3.5 m la tong hgp cua myc nuoc trieu cao 2.0 m ket hgp vai nuac dang do bao 1.5 m vai PA I dugc the hien tren hinh 5 (a, b).

Hrms [m]

100 200 300 400 500 (Grid spacing 5 meter)

Hinh 5a. Trw&ng song tinh todn bdo edp 9 v&i do cao song 2.01 m, chu ky 6 7 s lan truyin tren nin mwc nw&c tdng hffp 3.5 m vdo khu vwc Hai Hgu

v&i phwffng dn cdng trinh I

P H A N I - THlJY LUC, SONG BIEN VA PHONG CHONG LUT B A O . . 229

960 • • •- - 940 ••

920 ---;

900 --- 880 * 860

840 - ' •••

820 -- - 800 •-"--•;

780 • 7 6 0

7 4 0

5" 720 E

"Z 700 --

icint

g- 680

5 — 660

640 1 620 1 600 - -

580 - 1 5 6 0

540 • - 5 2 0

500 ^••

4 8 0

460 --- 440 -•

4 2 0

Hrms [m]

^

"^^H

^H

'^SM

|PI

• fSm

^-m^^jBfi :}M>ttifllli

I^^H

^^H

^^^B

TJSM

400 450 (Grid spacing 5 meter)

^ 1 ^ H

1 1 1 1 1 1 1 1 1 F J i ^

^ H ^ H

^ H • i

^M t^x

1 1

Atxjve 2 1 1 95

1 fi 1 fifi 1 5 1 35 1 ? 1 n.'i 0 9 0 7.'>

0 6 Oi.-) 0 3 ni,") 0 3eloM Unde

2.1 1.95 1.8 1.65 1.5 1.35 1.2 1.05 0 9 0.75 0.6 0.45 0.3 0.15 0 ned Value

Hinh 5b. Trw&ng song tinh todn bdo cdp 9 v&i dp cao song 2.01 m, chu ky 6.7 s lan truyin tren nin mwc nw&c tdng hgp 3.5 m vdo khu vwc Hdi Hdu PA I

(Khu vwc trich xudt sd lieu ke D4, de ngdm NI, di ngdm N2, ke D5)

Truang hgp song bao cap 12 vai do cao song 2.7 m, chu ky 10 s lan truyen vao khu vyc Hai Hau tren nen myc nuoc 3.2 m la tong hgp cua myc nuac trieu trung binh 1.2 m ket hgp voi nuac dang do bao 2.0 m vai phuang an cong trinh bao ve ba I dugc the hien tren hinh 6 (a, b).

Hrms [m]

Hrms [m)

^ H Above

• 1 24 1 1 ??

CZ] 2 - 3 18

r u 16

1 1 14 CJ 12

c n 1

E i a 08

^ 1 06

^M 04

^ 02

^ 1 I B I -0 2

^ H Below [ ~l Unde

26 26 24

1 4

08 0.6 04 0 -0 2 ned Value 100 200 300 400 500

(Grid spacing 5 meter)

Hinh 6a. Trw&ng song tinh todn bdo cdp 12 v&i dp cao song 2.7 m, chu ky 10 s lan truyen tren nin mwc nw&c tdng hffp 3.2 m vdo khu vwc Hdi Hgu

v&i phwffng dn cdng trinh I

PHAN I - THUY LUC, SONG BIEN vA PHONG CHONG LUT BAO.. 231

9 6 0 -

9 4 0 -

9 2 0 -

9 0 0 -

8 8 0 -

8 6 0 -

8 4 0 -

8 2 0 -

8 0 0 ;

7 8 0 -

7 6 0 -

7 4 0 ;

7 2 0 ;

7 0 0 -

6 8 0 -

660

6 4 0 ;

6 2 0 -

6 0 0 -

5 8 0 -

5 6 0 ;

5 4 0 -

Hrms [m'

11 - ' " 1 ' B H

^nOHHHj^^^^^^^lB

• S ^ ^ ^ ^ ^

^foHj^^^Hgl^

?

1

m&F^^^^^SSm

^^^m

^•R^^^^H ij^sw^^^S' '^•JuKsfi

^ ' " ^ ' . • ^ ^ ^ S

jg.._^ j w . ^ " L _ ^ V B E H

-fil^^L flnl

J^BJj^JT^^IJig^gW

^M^^BH^P^^ISSI

y'lB^^iLa1^g'3S5BMBB

^^^^[^nHpif^^^BBai

^l!^,' .•?'^*.Js^&fiiMSg3«!aPMM

" ^^j5^8HH

•liin'''?&; fc i B I ^ i B H

K^^^^^l Swi^mBHl

ViHH!R|H^H

Hrms [m]

^ B Above 2 6

^ ]

cn

CZl

cc

B a -0,2. 0 MH Below -0.2 I I Undefined Value 400 450

(Grid spacing 5 meter)

Hinh 6b. Trw&ng song tinh todn bdo cdp 12 v&i dp cao song 2.7 m, chu ky 10 s lan truyin tren nin mwc nw&c tdng hffp 3.2m vdo khu vwc Hdi Hdu v&i phwffng dn

cdng trinh I (Khu vwc trich xudt sd Ueu ke D4, di ngdm NI, de ngdm N2, ke D5)

Truong hgp song bao cap 12 vai do cao song 2.7 m, chu ky 10 s lan truyen vao khu vyc Hai Hau tren nen myc nuac 4.0 m la tong hgp ciia myc nuac trieu cao 2.0 m ket hgp vai nuac dang do bao 2.0 m vai phucmg an cong trinh bao ve ba I dugc the hien tren hinh 7 (a, b).

Hrms [m]

100 200 300 400 (Grid spacing 5 meter)

HnnsIm]

W i Above 2 6

CD CO CH CD CC

cn

MB Below .0 2 I I Undefined Value

Hinh 7a. Trw&ng song tinh todn bdo cdp 12 v&i dp cao song 2.7 m, chu ky 10 s lan truyin tren nin mwc nw&c tdng hop 4.0 m vdo khu vwc Hdi Hgu v&i PAI

PHAN I - THUY LLIC, SONG BIEN vA PHONG CHONG LUT BAO... 233

Hrms [ml

E m 760

^f:

z^ •.;*!

^J

400 450 (Grid spacing 5 meter)

Hrms [m]

^ B Above 2 6

^M 2 4 - 2 6 I I 2 2 - 2 4

2 2 I 1 8 - 2

CC CC

cc

B B Below -0 2 i I Undefined Value

Hinh 7b. Trw&ng song tinh todn bdo cdp 12 v&i dp cao song 2.7 m, chu ky 10 s lan truyin tren nin mwc nw&c tdng hffp 4.0m vdo khu vwc Hdi Hdu v&i PAI

(Khu vwc trich xuat so lieu ke D4, di ngdm Nl, de ngdm N2, ke D5)

Hnms [ml

(Cnd spacing 5 melei)

HH0CT_W2m01_wl27

Truong hgp khong co cong trinh song 2.01 tren nin nu-oc cao do 2.7 m m

(Grid spacing 5 nieier)

HH0CT_W2m01_wl35 Tru-ang hgp khong co cong trinh

song 2.01 m tren nen nifoc cao dp 3.5 m

ITinh 9. Trw&ng song tinh todn cde cdp bdo 9 v&i dp cao song 2.01 m, chu ky 6.7 i lan truyin tren nin mwc nw&c tdng hgrp 2.7m, 3.5 m vdo khu vwc

Hdi Hgu dia hinh ddy ttf nhien khdng co cdng trinh

PHAN I - THUY LUC, SONG BIEN vA PHONG CHONG LUT BAO.. 235

Hrms [m]

(Gnd spacing 5 meier)

HH0CT_W2m7_wl32

Tru'ong hgp khong co cong trinh song 2.7 m tren nen nyccc cao do 3.2 m

HH0CT_W2m7_wl40.dfs2 Truong hgp khong co cong trinh

song 2.7 m tren nin nuoc cao do 4.0 m

Hinh 10. Trw&ng song tinh todn cdp 12 v&i dp cao song 2.7 m, ehu ky 10 s lan truyin tren nin mwc nw&c tdng hffp 3.2 mvd4.0m vdo khu vwc Hdi Hdu dia hinh ddy

tw nhiin khdng co cdng trinh

Nhan xet caciclt qua va kit luan:

Vai PAI: Dp cao song tinh toan va he so suy giam song doi vai khu vyc Hai Hau dugc xac dinh tai cac diSm phia truac, phia sau cac dang cong trinh ke ehir TD4 vai cao dp dinh +3.5 m; de ngSm Nl, va diem sat ba tai khu vyc nay, de so sanh cilng tai cac diSm nay ngam pha song N2 vai cao dp dinh -1-1.35 m), tai khe ho giira hai cong

trinh ke chu: TD4 va se trich xuat so lieu song tinh toan trong truang hgp khong co cong trinh.

Cac so lieu dp cao song trich xuat the hien tac dpng ciia cac cong trinh doi vai qua trinh lan truyen song trong cac truang hgp tinh toan voi cac dieu kien song bao cap 9, cap 12 tren nen cac to hgp ND va thiiy trieu cho khu vyc Hai Hau vai PAI dugc tong kit (bang 2).

Bdng 2 Kit qud tinh suy gidm song khi truyen qua cong trinh phd song gdy boi bdi

C a c t r u o n g h g p t i n h t o a n

HaiHauCTPAl song 2.01 m m u c n u d c 2.7 m HaiHauCTPAl song 2.01 m mij'c n u d c 3.5 m HaiHauCTPAl sdng 2.7 m mi>c n u d c 3.2 m HaiHauCTPAl sdng 2.7 m m y c n u d c 4.0 m

BO cao s6ng [m]

H? so suy giam song Dp cao sbng [m]

Hp sp suy giam sdng Dp cap song [m]

Hp SP suy giam sdng Dp cao sdng [m]

Hp SP suy giam sdng

K h u v u c p h i a t r u o c c o n g t r i n h K d c h u

T(cao dp dinh +3.5 m)

1.415

1.605

1.768

2.076

De ng^m phci sdng (cao dp

dinh +1.35 m)

1.396

1.579

1.757

2.009

Khoang khehp' giOa hai cdng trinh

1.444

1.592

1.763

1.796

Khong cdng trinh

1.415

1.608

1.782

2.018

Khu vuc bo sau cong trinh

Ke chu" T (cao dp

dinh +3.5 m)

0.078 0.95 0.105

0.93 0.137

0.92 0.120

0.94

De n g j m pha sdng (cao dp

dinh +1.35 m)

0.547 0.59 0.917

0.42 0.905

0.49 1.318

0.35

Khoang k h e h d giu'a hai

cong trinh

1.046 0.28 1.279

0.24 1.256

0.29 1.331

0.26

Khong cdng trinh

1.075 0.24 1.247 0.22 1.321 0.26 1.594 0.21

Ket qua tinh toan cho thay trong truang hgp b6 tri cac cong trinh theo PAI tac dung giam song ciia cac dang cong trinh dugc the hien thong qua gia tri he s6 suy giam song:

1- Ke dang chu T vai cao do dinh +3.5 m co tac dgng tieu tan nang lugng song tot nhit vai gia tri ciia b? s6 suy giam song la 0.95, nang lugng song bi tieu tan gin nhu hoan toan vai dp cao song tai khu vyc truac cong trinh la 1.415 m va sau cong trinh la 0.078 m.

2- Doi voi de ngam pha song voi cao dp dinh +1.35 m, cho song tran qua nhung lam giam dp cao song tir gia tri 1.396 m xu6ng con 0.547 m vai he s6 suy giam song la 0.59.

- Cac ket qua ciia cac truang hgp tinh toan vai ciing mgt do cao song khi cao dp muc nuac bien dpng tir 2.7 m len 3.5 m lam he so suy giam song giam tir 0.59 xudng 0.42 doi voi de ngam pha song va hau nhu khong thay d6i ddi vai ke ehir T.

PHAN I - THLJY Lt/C, SONG BIEN vA PHONG CHONG LUT BAO... 237

3- Cac truang hgp dp cao song dugc xac dinh tai khoang khe ha giira hai cong trinh chiu tac dgng cua hien tugng nhieu xa dau ke va anh huang ciia dia hinh day thong qua hien tugng song va ciing lam giam dp cao song nhung he so suy giam la kha nho 0.28 gan nhu tuang ty vai trucmg hgp s6ng chi bi tac dpng cua dia hinh day khi chua c6 cong trinh vai he so la 0.24. He so suy giam song sau khoang khe ha giu:a hai cong trinh chi cao han khoang duoi 10% so voi truang hgp khong co cong trinh. Tir day can than trgng khi lya chpn kich thuoc nay.

4- Doi vai truang hgp thiet ke phuang an cong trinh 11: Ket qua tinh toan cho thiy tuong ty trong truang hgp b6 tri cac cong trinh theo phuong an I voi he so suy giam CO gia tri lech nhau khong dang ke.

5- KSt qua tinh toan cho thiy biic tranh cu the sy biln dpng ciia trucmg song do tac dpng cua he thong cong trinh tren bai truac de.

TAI LIEU THAM KHAO

[1]. Bao cao khao sat ven biln Hai Hau - Nam Dinh 2005- 2007 ciia Trung tam Dong lyc Cira song Ven biln va Hai dao - Vien Khoa hpc Thuy lpi Viet Nam.

[2]. Tomohiro Suzuki Delft University of Technology:Report on Subproject 2 'Wave Boundary Conditions' in sea dike research in Vietnam.Mission report January 2009 salt marsh. Proceedings of 31th Intemational Conference on coastalEngineering, ASCE.

[3]. Krystan W. Pilarzyk and Ryszard B. Zeider (1996) "Offshore Breakwaters and Shore Evolution control".

[4]. T.Sawaragi (1995), "Coastal Engineering: Waves,Beachs,Wave-Structure hiteraction" - Elsevier Science B.V.

[5]. Stanislaw R. Massel Ocean surface waves: their physics and prediction. Worid Scientific. 1998.

[6]. Goda Y., Random sea and design of maritime structures. World Scientific. 2000.