A I \ H H l t i f N G C I I A N l f t f C B I E I \ DANG Ttfl CONG TRINH BAO VE
CANG BIEN VA GIAI PHAP KHAC PHUC
THE EFFECT OF SEA LEVEL RISE TO HARBOUR PROTECTION C O N S T R U C T I O N A N D S O L U T I O N S
* TS. D A O V A N TUAN*
TOM TAT:
Do dnh hudng cua hien doi khi hdu, trdi dat dang nong len, mUc nUdc hien ddng cao so vdi trUdc day. Viet Nam co chieu ddi hd bien hoti 3000km, co rdi nhieu cong trinh ven bd, trong do cd cdc de chan song bdo ve cdng. Mtfc ntfdc bien ddng khong ddn thuan Idm tang chieu sau khu nUdc co cong trinh md con lam thay ddi thdng so'song tdc dong den cong trinh. Noi dung bdi viet neu cdc ket qua dnh hudng cua nUdc bien dang tdi thong so'song, cao trinh, kich thudc cd ban cua cdng trinh i e chan song mdi nghieng vd tUdng ddng, tii dd dun ra cdc gidi phdp khac phuc mang tinh dinh hudng.
ABSTRACT:
Because of the effect of climate changes, the Earth has been hotter, the sea level has risen higher than before. Viet Nam has a 3000km-length coastal line, there are many coastal con- structions including break waves for protecting harbours. The sea level rise not only makes the construction's water depth increased but also changes wave's parameters of constructions.
This article is giving results of the effect of sea level rise on wave's parameters, elevations, basic dimensions of shelving break wave and vertical wall, then giving solutions to repair.
1. Dat van dc
Su1 bien doi khi hau dang dien ra tren toan cau trong the' ky X X I , day la van de quan trong. Viet Nam la ntfdc cd bd bien dai, cd nhieu cdng trinh ven bien, trong do co cac de chan song bao ve cang. Do anh htfdng ciia khi hau va nude bien dang, cac cdng trinh nay cd the khdng dam nhan dirdc cac chtic nang da dude thiet ke. Viec danh gia sit anh hiidng ciia bien dd'i khi hau, nude bien dang tdi cdng trinh bao ve cang bien mang tinh quy luat: nhu* thay ddi thdng so' sdng, tai trpng, kich thufdc cd ban ciia cdng trinh de luting diing, mai nghieng la rat can thiet. Hien cac nghien cu*u trong nu*dc con rat sd sai. Noi dung bai viet nham neu cac ket qua nghien ciiu da dat dupe ciia tac gia ve linh vtfc nay.
2. Vai t r o , ke't c&'u cua de chan song vdi cang bien
Vdi cac cang d viing bien hd de tranh tac dung ciia sdng vao tau thuyen dang khai thac trong cang, ngUdi ta phai lam de chan sdng, tac dung che chan ciia de chan sdng la lam cho chieu cao sdng trong be cang giam xudng tdi mdt gia tri chap nhan dtfdc. V d i mot so cang hai dao, be cang con la ndi cho cac tau thuyen tranh bao, dac biet la cac thuyen danh ca (cang ca Phii Quy, cang quan stf Song Tu*
Tay v.v...). Theo hinh dang mat cat ngang ket ca'u, de dirdc phan thanh: de ttfdng dtfng trpng ltfc, de chan sdng mai nghieng, de chan sdng bang ctf, cpc, ket cau de hon hdp (niia dtfng, ntfa nghieng), de thuy khi va cac loai ket cau dac biet khac.
o.o
a) 0.0
a. Ttfdng dtfng trpng ltfc; b. M a i nghieng; c. Bang ctf va cpc; d. Be hon hpp.
Be chan la cong trinh ven bien nen chiu tac dpng manh va trtfc tiep cua bien ddi khi hau va ntfdc bien dang.
3. K i c h ban bien doi khf hau, ntfdc bien dang
Bien ddi khi hau la mot trong nhffng thach thtfc ldn nhat vdi nhan loai trong the ky X X I . Bien ddi khi hau se tac dpng nghiem trpng den san xuat, ddi song va mdi trtfdng tren pham v i toan the gidi. Nhiet dp tang. Mtfc ntfdc bien dang gay ngap lut, gay nhiem man nguon ntfdc, anh htfdng den ndng nghiep, gay
rui ro ldn ddi vdi cdng nghiep va cac he thdng kinh te xa hpi.
Bien ddi khi hau trong the' ky X X I phu thupc chu yeu vao mtfc dp phat thai khi nha kinh, ttfc la phu thudc vao stf phat trien kinh te' - xa hpi. V i vay, cac kich ban bien ddi khi hau dtfdc xay dtfng dtfa tren cac kich ban phat trien kinh te - xa hpi toan cau.
Cac kich ban ntfdc bien dang cho Viet Nam dtfdc tinh toan theo kich ban phat thai thap nha't ( B I ) . Kich ban phat thai trung binh (B2) va kich ban phat thai cao nha't (A1FI).
Bang 1. Mtfc ntfdc bien dang so vdi thdi ky 1980-1999
Kjch bin Cac rftfic thef i gian.-ciia thi' ky 21 Kjch bin
2020 2030 | 2040 2050 2060 1 2Q7Q 2080 I 2090 | t 00 I Thap (81} | 11 17 \ 23 28 35 | 42 50 5? 85 j Trung binh (B2) i 12 17 j 23 30 37 | 46 54 64 I 75 I Cao ?A1F!> | 12 17 OA 33 44 j 5? " ! 86 ] " !8Q \ Be nghien ctfu anh htfdng cira ntfdc bien
dang tac gia lay cac gia tri ntfdc dang theo ba kich ban cua nam 2100.
4. A n h htfdng cua ntfdc bien dang tdi thong so'song
Be danh gia anh htfdng ciia ntfdc bien dang tdi thong so sdng, tac gia lay dia hinh khu vtfc de chan sdng cang ca Ngoc Hai, Bo Sdn, Hai Phong de tinh.
6
Hinh 1. Sd do khu vtfc tinh sdng de chan sdng Ngoc Hai, Bd Sdn
So Tet Tan Mao 1+2 • Nam 2011
Viec tinh toan thong so'sdng dutfc thu'c hien bang M I K E 21.
4.1. Dia hinh khu viic tinh song
Bathymetry 2300000
2290000 -.
2280000 2270000 2260000 2250000 -' 2240000 - 2230000
J las
111?'
080000 600000 620000 640000 660000 6S0OOO
(Titter _ 1 -7.5 I I -10 I 1-12,5 I I -IS IMS-1?,5 EH -20 US-22.5 -30 -32 5
2? 5 -25 -30 -32.5
I I Undefined VSlus
•4
•7.5
•10 12.5 17.5 •K -20
Hinh 2. Dia hinh day bien khu vifc tinh sdng 4.2. Ket qua tinh song
So' lieu nude bien dang difdc lay vdi ba Chieu cao sdng lay tai dau de vdi toa do:
kich ban la 0,65; 0,75; va 1,0 m de'n nam 609471.640,2293110.414 2100.
Sign, Wave Height
Pbovt 10,4 plj Ct P. • !0.4 I *- S.S 5:4- 7.2 M 5.C 5.4 W 45- 3.4 ES3 4- 4 .4 H 3i 4
Hinh 3. Ke't qua chieu cao song hudng gid bat ldi
4.2.1. Chieu cao song khdng tinh mtdc bien ddng
Bang 2. Thong sd song tdi khi khdng cd nirdc bien dang
Song Hs(rn) H ,H (m) T(s) Birdc song (m) G6c toi (do)
Tdi 2.64 4.4 5.7 51.0 139
Nhieu xa 1.02 1.7 4.3 29.2 113
4.2.2. Thdng so song khi cd nuac bien ddng - Song tai:
Bang 3. Thong so song toi
Do dang (m) Hs( m ) H1 % (m) T(s) Biroc song (m) Goc toi (do)
0,65 2.89 4.8 6.0 57.0 139
0,75 2.93 4.9 6.1 58.0 139
1,0 3.02 5.0 6.2 60.4 139
- Song nhieu xa:
Chieu cao song nhieu xa lay dang sau de v o i toa do: 608899.659, 2292775.956
Bang 4. Thong so song nhieu xa
Do dang (m) Hs(m) H,% (m) T(s) Buoc song(m) Goc toi (do)
0,65 1.10 1.8 4.5 32.2 113
0,75 1.11 1.8 4.6 32.8 112
1,0 1.13 1.9 4.7 34.2 112
4.2.3. Sir thay ddi tuong ddi so vdi khi khdng cd mtdc bien dang.
- Song tdi:
Bang 5. Dg gia tang thong so'song t d i
Do dang (m) Hs (m) Hi% (m) TOO Buoc song (m) Goc toi (do)
0.65 0.10 0.10 0.06 0.12 0.00
0.75 0.11 0.11 0.07 0.14 0.00
1.00 0.15 0.15 0.09 0.18 0.00
8 So Tet Tan Mao 1+2 • Nam 2011
Song nhieu xa:
Bang 6. Do gia tang thong so' song nhieu xa.
Do dang (m) Hs(m) H i % (m) T(s) Lamda (m) Goc toi (do)
0.65 0.07 0.07 0.05 0.10 0.00
0.75 0.08 0.08 0.06 0.13 0.00
1.00 0.11 0.11 0.08 0.17 -0.01
DUa vao ket qua tinh toan cho thay chieu cao song va chieu dai song thay ddi tUOng dtfdng nhau, ntfdc dang cang nhieu thi ty le tang chieu cao song va chieu dai song cang ldn, ldn nhat co the dat 15-18% ciia sdng tdi, sdng nhilu xa thay ddi it hdn chiit it. Chi cd hai dai ltfdng it thay ddi la chu ky va goc tdi ciia sdng. Chieu cao sdng va chieu dai sdng, gdc tdi ciia sdng la cac dai ltfdng tham gia trtfc tiep vao cac cdng thtfc tinh toan kha nang chiu tai ciia cdng trinh.
Nhtf vay cd the thay khi ntfdc bien dang
khdng ddn thuan lam tang mtfc ntfdc ma cdn lam cho chieu cao, chieu dai ciia sdng, dieu nay se gdp them phan anh htfdng de'n kich thtfdc cd ban ciia cdng trinh, ngoai ra con anh htfdng de'n do ben cau kien cdng trinh.
5. A n h htfdng cua nude bien dang tdi kich thtfdc ctf ban cua cong t r i n h
Dtfa vao ket qua thay ddi ciia thdng sd' sdng, ap dung cac cdng thtfc tinh toan ttfdng tfng, tac gia da xac dinh dtfdc stf thay ddi ciia cac cau kien cung nhtf kich thtfdc cd ban ciia cong trinh.
5.1. Cao trinh
B a n g 7. D o gia tang mire nuoc tong the
STT Hs (m) % Hs Do dang (m) Tong (m)
1 2.64 0.10 0.25 0.65 0.90
2 2.64 0.11 0.29 0.75 1.04
3 2.64 0.15 0.38 1.00 1.38
Ty le phan tram so vdi chieu cao cdng trinh:
5.2. Chieu cao cdng trinh
Bang 8. Do gia tang so vdi chieu cao de STT Do dang (in) T6ng (m) D9 tang
1 0.65 0.90 0.14
2 0.75 1.04 0.17
3 1.00 1.38 0.22
5.3. Be rdng de
Trong ltfdng kho'i phu de mai nghieng - Kho'i phii phia trirdc:
Bang 9. Do gia tang trong lifdng kho'i phu STT Do dang(m) Do tang khoi lirong
1 0.65 0.31
2 0.75 0.37
3 1.00 0.50
- K h o i p h u phia sau:
Bang 10. Do gia tang trong luong khoi phii
STT Do dang (m) Do tang khoi lirong
1 0.65 0.23
2 0.75 0.27
3 1.00 0.35
Be rdng de mdi nghieng
Bang 11. Do gia tang ciia be rong de mai nghieng
STT Do dang (m) Do tang be rong
1 0.65 0.10
2 0.75 0.11
3 1.00 0.15
Tdi trong len tudng dimg
Bang 12. Do gia tang ciia tai trong song len tuong diing STT Do dang (m) Do tang tai trong song
1 0.65 0.20
2 0.75 0.23
1.00 0.31
10 So Tet Tan Mao 1+2 - Nam 2011
Be rong twang dung
Bang 13. Do gia tang ciia be rong tuong diing STT Do dang (m) Do tang be rong
1 0.65 0.20
2 0.75 0.23
3 1.00 0.31
Tren day la cac ket qua sO bo cho thay stf thay doi kich thtfdc cd ban ciia de chan sdng do bien ddi khi hau, cu the la ntfdc bien dang, chtfa tinh den stf manh len ciia cac cdn bao do nhiet do tang.
6. Phtfdng htfdng khac phuc
Vdi muc tieu dat ra can phai nang cap cac de chan song da dtfdc vay dtfng (trtfdng hdp gia dinh), vdi hai ket cau dien hinh la de ttfdng dtfng va mai nghieng, tac gia de xuat cac htfdng giai quyet nhtf sau:
6.1. De tudng ddng
Vdi ttfdng dtfng, viec nang cao trinh de cd the thtfc hien de rang bang viec them khdi be tong dinh cd lien ket vdi cdng trinh ben tren co san, tuy nhien viec md rdng be rong thtfc stf la khd khan. Cach ddn gian nhat la bien de ttfdng dtfng thanh de hon hdp vdi phia ngoai la mai nghieng, ben trong la ttfdng dtfng, cac tinh loan cu the khi thiet ke se xac dinh dtfdc chinh xac cac kich thtfdc.
6.2. De mdi nghieng
Vdi de mai nghieng viec nang cao trinh va md rdng be rdng ddn gian hdn de ttfdng dtfng, each ddn gian nhat la phii len be ngoai ciia mat trtfdc va mat sau de chan sdng mai nghieng bang khdi phii mdi, cao trinh dinh hoan toan cd the nang cao bang each gia tang khdi be tdng dinh. Cac kich thtfdc cu the se dtfdc xac dinh trong giai doan thiet ke.
7. K e t luan
Noi dung bai viet da xac dinh dtfdc mot so"
quy luat the hien stf tac ddng ciia bien ddi khi hau, ntfdc bien dang den cdng trinh bao ve cang, nhtf stf thay ddi thdng sd'sdng, chieu cao de, be rdng de, trong ltfdng khdi phii, tai trong len ttfdng dtfng. Ngoai ra cdn de xuat bien phap mang tinh dinh htfdng de khac phuc nang cap de trong trtfdng hdp can thiet.
Cac ket qua nghien ctfu tren co the lam tai lieu tham khao cho nhffng ngtfdi cung nghien ctfu trong linh vtfc ttfdng ttf, nhffng ngtfdi lam cdng tac thiet ke, cai nhin tdng quat mang tinh dinh htfdng.
T A I LIEU T H A M K H A O
1. Tai trong va tac ddng (do sdng va tau) len Cong trinh thuy. Tieu chuan thiet ke 22TCN222-95, Ha noi bo Giao thdng van tai 1995.
2. De bien. Tieu chuan thiet ke. Bd ndng nghiep va phat trien nong thon. Ha noi 2002.
3. Coastal engineering manual. Us army 2000.
(*) T S- m ° v a n T u a'n " Kboa Cong trinh thiiy, Trtfdng D H H H , Bo G T V T
