Nguyên nhân và giải pháp khoa học công nghệ phòng chống xói sạt các đoạn bờ trọng yếu của bờ biển bắc bộ hội thảo xói lở bờ biển việt nam và các biện pháp phòng trán

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185193

NGUYEN NHAN VedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
A GIAI PHAp KHOA HOC CONG NGHE
PHONG CHONG XOI SAT CAC'DOAN BCUA BO BIEN BAC BO
"

Dinh Van Huy.Tran

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Dire Thanh, Tran Dinh Lan, B u i Van Vuong
Vien Tai nguyen va M6i tnrong bien

MODAU

a dai ven bien, co
Xoi sat bo bien lit mot trang nhirng thien tai n a n g ne n h a t XWVUTSRQPONMLKJIHGFEDCBA
xu huang tang len gan day tren quy mo ro a n cau. Nhieu quoc gia co bien da co
nhirng no hrc nghien ctru d~ hieu ro nguyen nhan va tim giai phap phong chong.
Mot so niroc nhu Lien X6 c u , Ha Lan, Phap, My, Nhat da co nhfrng kinh nghiem

va thanh cong trang Iinh vue nay.
Trang nhirng nam vira qua, xoi sat bo bien Viet Nam noi chung, bo bien
Bac B(>noi rieng, dien bien her sire phirc tap va gay nen nhirng hau qua nang ne
cho dan sinh, kinh te nhir: mat dat nong nghiep, nhiern man, pha huy nha cira,
cac cong trinh kien true ... Mat khac, sir tap trung dan so va nhip do, qui mo phat
trien kinh te - xa hoi dai ven bien dang tang manh, can diroc dam bao phat trien
ben vimg. VI vay, viec tirn hieu nguyen nhan va cac giai phap khoa h9C cong
nghe d~ giup bao ve bo bien, dac bier la cac doan bo tro n g yeu cua b e bien Bac
B(> da tra thanh mot doi hoi cap bach, mot nhiem vu quan trong diroc Chinh phu
cling nhir cac co quan, Ban nganh lien quan dac biet chti y trang nhirng nam cuoi
cung cua the ky x x .
Da co nhieu cong trinh nghien ctru tirn hieu nguyen nhan va cac giai phap
phong chong xoi sat 166 cac khu vue bo bien Bac B¢ [2, 3, 5, 6, 7, 8, 9, 10]. Bai
bao nay la ket qua cua qua trlnh nghien cuu, tim hieu nguyen nhan va cac giai
phap c6ng nghe phu hop voi hoan canh kinh te cua Viet Narn noi chung va cua
dia phirong noi rieng d~ phong chong xoi sat bo bien cua Vien Tai nguyen va
M6i tnrong bien.
1. Nguyen nhan xoi sat cac doan bo trong yeu cua bo bien Bac B<)
Ket qua cua D V an doc lap cap Nha ruroc KHCN - 5A "Nghien c iru dir bao,
phong chong sat 16 bo bien Bac B9 tir Quang Ninh den Thanh Hoa" do Phan vien

Hai dirong h9C tai Hai Phong nay la Vien Tai nguyen va M6i tnrong bi~n chu tri
da xac dinh bo bien BtlC B¢ co 2 doan bo bi xoi sat nghiern trong, do la dean be
dao Cat Hai, Hai Phong dai 6,4 km va doan b o huyen Hai Hau, Nam Dinh da!
1 7 ,2 km.
1.1. Nguyen

nhan

xoi sat bo bien Cat Hili

Xoi 16 khu Vl!C trong diem Cat Hili co nguyen nhan sau xa lien quan den
nguon goc hlnh thanh va tien hoa cua dao cat. Dao diroc hinh thanh trong dieu
kien boi tu chau th6 khoang 2 - 1 nghln narn tru c e . Khoang 5 - 7 tram nam tro
lai day, muc bien dang cao do ca nguyen nhan chan tinh va kien tao, nguon bdi
tich giarn han, thuy trieu manh len va che do cira song chau th6 dirong bien
thanh chau th6 am (hinh pheu) va dao bi xoiRQPONMLKJIHGFEDCBA
1 0 trang dieu kien dong lire moi voi
rnirc xarn thirc co so nang cao va nang luong song manh len. Xoi 1 0 co xu the dai
185


lau do ket hop ca xarn thuc ngang gay sat 16 bo va bao man mat day siren boedcbaZYXWVUTSR
n g a m sat b o .
.
Nguyen nhan true tiep xoi sat bo dao la su thieu hut khong den bu boi tich
khoang 342.800 tan/nam. Ly do thieu hut b o i tfch chu yeu la dong chay trieu len
co toe dQ va thai gian Ian hon him dong xuong da dira boi tfch ra khoi khu vue
ven dC10 qua hai lach Hoang Chau va Got dira V~IOlach Nam Trieu va Lach
Huyen gap phan gay sa boi nghiern trong lu o n g VaG cang Hai Phong. S6ng co
vai tro tnrc tiep gay sat 16 bo va khuay due day d~ dong chay dira vat lieu di.
Dong bun cat tong hop phan ky 6 giira (phfa ngoai Gia LQc), di chuyen bun cat
doc bo di ve hai phfa dong V~lray, xoi sat chu yeu VaG rnua gio ra y nam co rrura
bao (thang 6 - 9). Duong bien xoi sat va bao man day 6 do sau 2m. Ngoai dQ
s a u 2m I~Iv u n g boi tu .
1.2. Nguyen nhan xoi sat bo' Hai Hau
Xoi 16 khu trong diem Hui Hau co nguyen nhan sau xa la sir chuyen pha tir
boi sang xoi cua mot dean bo chau tho, lien quan den qua trlnh chuyen nhanh
chfnh cua song Hong tir song So tnroc day d6 VaG ven bien Hai H~u sang vi tri
cira Lan roi cira Ba Lat nhir hien nay. H~ thong de dap nhieu doi da lam mat

nguon boi tich tir song cho ven bo Hai Hau, tao nen sir bo: Ian nhanh bat thuong
cua cira Ba Lat. cira Day va lam bo Hai H~u lui sau VaG vung khuat phu sa song
dira ra ven bo. Sir thieu hut boi tfch nghiem trong trang dieu kien ngap chirn kha
manh (ha kien tao va nang chan tinh) c1agay xoi sar bo Hai Hau.
Nguyen nhan true tiep xoi sat bo Hai Hau la sir thieu hut boi tfch khoang
1.796.000 tan/nam do di chuyen doc bo ra khoi khu vue ve phia tay nam va di
chuyen ngang phan tan ra sau. Song co vai tro hang dau gay xoi sat bo va di
chuyen boi tich sat bo. Dong chay tong hop co vai tro Ian nhat ph an tan boi rich
di khoi khu vue, Mua xoi sat trung VaG dau mua gio dong bac (thang 11 - 12) va
khi co bao. Duong bien xoi sat va bao man day bin den c1Qsau 10m. Xoi sat
manh liet tir dQ sau 2m tro vao. Bao man day dat den do sau 10m. Ngoai do sau
10m la vung boi tu yeu.
2. Giai phap cong nghe tal cac trong diem
2.1. Cat Hai
Ten Cong Trinh:RQPONMLKJIHGFEDCBA
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x o i s a t h i! d d o

H di Phong

k h o a h o c , th u c tie n v a n g u y e n

u ic

C O SO' khoa hoc cho giai phap dua tren viec xac dinh nguyen nhan xoi 16 bo'
dao tren quan diem dia chat dong hrc va hoc tap, tham khao cac giai phap phong
chong xoi 16 bo bien c1a va dang duoc ap dung tren the gioi. Doi voi tnrong hop
dao Cat Hai, nguyen nhan sau xa la su dang cao mire mroc bien ket hop v c i hoat
dong rnanh cua dong trieu trang dieu kien bci tfch bi thieu hut va phan tan manh,
yeu to tac dong cua con nguoi ChLIyell la chat pha rung ngap man, nao, vet luong
ben. Nguyen nhan true tiep la do sir thieu hut khong den bu boi tfch 6 ven dao
ChLIyeu gay ra boi hien tuong bat dang trieu 6 khu vue ven dao. Song dong vai
tro true tiep gay sat 16 bo va khuay due day d~ dong trieu mang vat lieu di.
186


Thirc tienXWVUTSRQPONMLKJIHGFEDCBA
a Cat Hai cho thay cac ke mo han diroc xay dung thir nghiern tir
1995 dil phat huy tac dung tot trong viec bao ve de bai. Qua mot t h a i gian theo
doi thay rang can dieu chinh m o t so thong so ky thuat cua he thong de dat hieu
qua cao h o n .
Giai phap duoc lua chon dua tren cac nguyen tac c o ban sau:
- C6 hieu q U {1 cao, dam bao bo bien khong bi x6i sat lo; tao su 6n dinh
lau dai cho sir phat trien ben virng kinh te - xa hoi khu vue.
- C6 tfnh kha thi cao nho dua tren nhirng can err khoa h9C tin cay ve dien
bien, nguyen nhan, c o che x6i sat va phu hop voi dieu kien kinh te xii
h o i Viet Nam.
- Khong gay nhirng tac dong tieu circ den moi tnrong sinh thai va cac
cong trinh khac a trong khu vue hoac Ian can, dac b ie r, khong gay hieu
irng sat 10'cho cac doan bo Ian can.
T h i e t k l RQPONMLKJIHGFEDCBA

S O ' b i) c o n g tr in h

•

V i tr i

I'a

q lly

/7/0 c o n g t r i n h

H~ thong ke trien khai tren toantuyen
de bien dao Cat Hai, theo phuong an
dang trien khai gom 14 ke, moi ke dai 76m, khoang each giira hai ke tir 250 den
400m. Trang d6 ke eMu tien diroc thi cong c o ban dira tren thiet ke thir nghiern do
Phan vien Hai dirong h9C tai Hai Phong thirc hien iT r d n D u e T h a n h v a n n k ,
1991) theo qui trinh cua CERC ( C E R C , 1984), cac ke can lai deu diroc thiet ke '
dira tren thiet ke n ro n g n r n h ir ke so 1 nhirng c6 thay d6i ve chieu dai va d(> cao
dinh ke. Cho den nay dii c6 tong so 7 mo han diroc xay dung. 00 moi thir
nghiem nen can phai c6 nhirng dieu chinh de he thong ke phat huy duoc tac dung
cao hon. Cac ph an can dieu chinh bao gom ca cac thong so cau true cua mot rno
han cling nhu khoang each giira cac mo han.
•

C d u tr u e c u a m o t

J .:.e m o h a n

Cac thong so ky thuat cua mot ke diroc dieu chinh nhu sau:

(0) dai 90-l00m
voi dau ke ap bo cao 4m/OmHD, gem 2
doan: Doan thir nhat (01) phia trong, dai 20m can c6 do cao 6n dinh 4m/OmHD
d6 tao them bai (berm), Doan thu hai (02), phia ngoai, dai n r 70-80m. Thong
th u o n g 02 g e m 2 ph an :D2a v a 02b. Trang d6 02a la d o a n n o i giira 01 voi 02b,
c6 d(> doc tuong d tro n g g6c doc mat bai tv nhien, khoang 2-3" nharn m u c dich
tao ra bai moi n6i cao lam giarn nang lirong s6ng, bao ve phan them bai phia
trang. Doan 02b la ph an dau ke phia bien c6 chieu dai lay theo kinh nghiern la
khoang 20-25m. Dean n~IY thuong c6 d(> eao Ia I m so v o i mire nuoc thap nhat,
c6 the e6 hinh non.
C h ie u

dai ke

C h ie n r o n g d in h k e :

2m.

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D du

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b ie n

voi d(> doc mai l:3

rong 4m, eao 0,5m

1 8 7 tsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA


Kef

cdu

ke:

Than ke gorn hai lop chinh: lop bao ngoai bang da cap phoi

kich thiroc Ion (~ 240 kg), lop trang dung vien da nho hen, nhirng khong diroi
1/25 trong luong vien da cua lop ngoai, giira hai lop co lop dem dung vai
geotextile.Chan
khay dung vien da tha roi.XWVUTSRQPONMLKJIHGFEDCBA
•

e a c h g iiia c a c m o h im

K hodng

Khoang each giira cac mo han can dam bao theo he so 2 - 3 Ian chieu dai
than ke (he so kinh nghiern). Doi voi khu vue nay sau thai gian thir nghiem voi
khoang each gitra cac ke Ion hon 2 Ian chieu dai than ke, tac dung cua ke bi han
che, kh6ng tao ra cac cung boi noi 6 dean giira hai ke nen can dieu chlnh khoang
each giira cac mo han bang 2 Ian chieu dai than ke nrc la van khoang 180 200m.

•

B ie n p h d p

c h o n g lu n v a x 6 i !d c h a n c o n g tr in h

Do dac diem nen dia chat cua vung bai, cac
dung trang cac c6ng trinh thuy lei can duoc thay
tang kha nang chiu tai cua nen cat nira chay, vira
1 0 trang dieu kien dong luc bi~n 6 giai doan
bi xoiedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
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T r in h

lop be dern rang rao duoc sir
the bang CQC van yay vira lam
bao ve chan c6ng trinh kh6ng
dall ke moi diroc xay dung.

tu x a y d u n g h ¢ th o n g k e

Theo phuong an do Phan vien Hai dirong hoc t<;liHai Phong d~ xuat tnroc
day, cac ke dau tien diroc xay dung khep dan tir hai phia Hoang Chau va Ben Got
v~ phia vung Gia LQc (hlnh 1). Nhu vay dam bao dtroc kha nang cung cap boi
tich cho tat ca cac ke va kh6ng gay hieu img xoi 16 manh do thieu hut boi tich.
Day la phircng an phu hop cho doan bo nay.

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Khi he thong ke diroc xay dung hoan chinh, mot he thong bai moi se hlnh
thanh voi mat cat bai day du, tire la hinh thanh them bai, mat bai doc khoang 3°.
Su hinh thanh them bai doi hoi thai gian, nhung thuc te 0 Cat Hai, them bai dil
diroc hlnh thanh t<;11m ot so khu vue nhu bai hlnh thanh do keedcbaZYXWVUTSRQPONMLKJIH
0 gan b e n Got.
Tren blnh do bai giira hai ke se co hlnh canh cung 16m ve phia l~ICdia. Sau mot
nam, thuong be mat bai diroc boi cao trung blnh O , S m , noi boi cao nhat co th~
dat toi 1 ,S - 2m Khi them bai hinh thanh v6i chieu rong khoang 20m thi tac dung
bao ve bo duoc phat huy toi da. M~t khac, srr hinh thanh he thong bai bien se
mang lai loi Ich kinh te cho huyen dao: Day se la noi tap k e r cho cac phuong tien
danh ca nho. cling se la nhirng bai tam dep, phuc vu du lich, giai tri.

2.2. Hai Hau
Ten Cong Trinh:

Xdy

song phong

x o i s a t b a b ie n H d i H a u , N a m

Co

so '

khoa

chong

dung

h o c , th u c tie n

h e th o n g

va nguyen

k e m o h im

nuoi

bdi kef hop

voi ke phd

D in h .

td c

Viec X<1c dinh dung nguyen nhan gay xoi 16 bo va bai bien cung voi kinh
nghiern thirc te 0 khu vue Cat Hai la c o s6 khoa hoc vfrng chac cho giai phap.
Nguyen nhan sau xa duoc xac dinh la su thieu hut boi tich cue bo co tinh pha
doan tren phong nen boi tu lau dai ket hop voi nang hrong song cao pha huy cac
dean bo cau tao tLI'tram tich bo roi va di chuyen mat boi tich. Tac dong cua can
nguoi thuc d~y qua trinh nay xay ra rnanh me hon. Nguyen nhan tnrc tiep chu
yeu la di chuyen boi tich doc bo do song hlnh thanh vao mua gio dong bac ket
hop dong trieu xuong dira boi tich ve ph fa tay nam, do sir phan tan manh me boi
tich tir bo ra day de tao can bang trac dien ngang, trang dieu kien mire bien dang
ket hop dao dong trieu 16n ky trieu cuong, mroc dang gio mua va dang trang bao.
Song co vai tro hang dau gay xoi sat 16 va di chuyen bun car doc bo.
Thuc tien 6 khu vue Hai H~u, da co nhieu 10<;1ike duoc xay dung, nhung
hieu qua thap va tac dung rat khac nhau. Cac dang ke mo han vuong goc bo va
ke 0 vuong, la su ket hop ke rno han vuong goc bo va ke dQC bo cho nhirng ket
qua kha quan, tuy nhien can co rat nhieu han che nhir danh gia trong bao cao
chuyen de ve giai phap kha thi phong chong xoi 16.
Cac tac gia cua bao cao nay cling dil co nhirng quan sat thirc te ve giai phap
cong trinh 10<;1inay trang dieu kien tuong nr tai mot so ruroc tien tien nhu Ha
Lan, Dire va Phap. Hon nira, cac ke dang thir nghiern 0 Cat Hai, voi qua trinh
thiet ke co co so khoa hoc va thirc tien virng chac, cling chirng minh cho tfnh kha
thi cao cua gi~li phap cong trinh nay.
Viec hra chon giai phap tuan theo 3 nguyen
cho khu virc Cat Hai.
T h ie l k e ' so ' b ¢ c o n g
•

V j tr i v a q u y

tac nhu giai phap cong trinh

tr in h

mo

H¢ thong ke se duoc trien khai xay dung tren toan tuyen de, bai xung yeu
trang pharn vi huyen Hai H~u, tir Van Ly den Hai Thinh, dai 17,2 km. Do dac
189


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each

dean

3 - 4

v a k ip

th a i

gai phap
khi

g iira

ke

c o th ~ tie n

N hu

d ie u

c h in h

he

va phu

vay

xay

cac

cha

qua

la

th e a

th u a t.

ly ,

T ra n g

v a v ira tra n g

khoang

trin h

dung

quan

v ie c

so ky

nho

cang

se

xay

bat dau

c a c th o n g

th o n g

th u o c

hanh

se de dang

c h in h

h o tro n h u

hoan

cac

bo, nen
nho.

C ~ 1 Il1

68

d o i,

-

d ie u

khu

ke

(tuy

c h in h

cac

86

cho phu hop),

Cdu true mo han
tru e

C au
th e

C l;!

C ac

(; tirn g

th o n g

han

mo
dean

s o e lm

xay

ve

bo
mo

dung

u ro n g

tv p h a n

Doan trong
25m

co

d¢

khoang

cao

khong
HD.

ve

de,

Doan ngoai

tie p

c o ta c d u n g

caa

se

nen

la y

baa

g ia m

la

khoang

dan
1m

0 ,1 0 0

de

th a y

d o i,

hoac

be

d ie u

k ie n

v a m a t c a t b a i.

rn o n g
k ie n

L05-130m

tir

b a i (D 1 ) k e o

u ro n g

nay

th e a
do

lin g

duoc

(D 2 a

doc

voi m uc

so

vao cac

khoang

tra n g

nen

v a o d ie u

tre n .

phuong phap

voi

C a t H a i.

c h a rt

D oan

th u o c

tru e

n It n h ie u

xay

trie u

rm rc
dung

ve

dai

n h a rn

p h ia

b ie n

d a i tir 2 0 -

caa

nhat

tra n g

m uc

d ic h

ta o ra th e m

khu

vue,
bai

bo.

th e a

- 0 ,1 2 5

d6i

th u o c

lire , c a u

d6i phu

cha

tin h

g ia p

4 , O m /O m

th a y

v irc p h u

khu

to d o n g

s e th a y

Chilli dai thdn ke:
x a c d in h

yeu

cac

han

tro n g

cua

trie u

mm

va

nhu

D 2b)

m at

co

b a i,

c h ie u

tu y

dai

n h ie n

nhat. V ai t h a n h
do d o c t u n h i e n

th a p

(; d a y ,

khoang

do

phan

- 110m ,

6 dau

cao

m at

85

do

hat

d¢

ke

p h fa b ie n

cat

b a i tra n g

bai se dat khoang

1 .5 -

2 .0 " .
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th o n g

k e rn o h a n

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th ie t

khac

do

nhu

ke cho

ro n g

d in h

ke, d¢

doc

m a i,

ket cau

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nhir

C a t H a i.

• Call true doan ke pha s6ng
Ke
la c a c
M ot
nhau

duoc

ke

pha

h e th o n g

gan

vuong

song
ke

m ot khoang

Chieu dai

nay

pha

goc
se

voi cac

mo

huang

song

co

song

se g o rn

nhat

d in h .

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ke I:

m oi

cac

han

song

dean

dean

tre n ,

ke

ke nay

ta o

voi

th a n h

duong

bo

(s e g m e n te d

co

c h ie u

dang
va

c h ir T . N g h ia

d in h

b re a k w a te r)

d a i th a y

d6i

tra n g

song

to i.

dat each

khoang

1 = 1 0 0 -1 2 0 m
C

hieu cao ke:

c h ie u

caa

d ie m

m oi

n o i,

ke

se

bang

khoang

lrn

c h ie u

so

voi

cao
d¢

cua

caa

ke

m at

mo

han

ta i

b a i ta i d i~ m

noi .
Chien rong dinh ke:
D6 d(3C mdi:

c h ie u

ra n g

d in h

ke m o

han, 2m .

1 :3

Kef cdu: giong
•

bang

n h ir

ke mo han.

Khoang each giiia cac ke
K hoang

c h ie u

d a i th a n

each

g iira

ke. 6 khu

cac

rn o

vue nay

han:

la y

khoang

th e a
each

190

he
g iira

so
cac

k in h

n g h ie rn ,

rn o h a n

bang

2 -3

Ia n

la y tir 2 0 0 -2 5 0 m .


Khoang

each giira cac doan ke pha s6ng duoc xac dinh bang t6 hop cac

dieu kien:

- 2< B/L<5, voi B= khoang

.

each giira hai ke; L= biroc s6ng trong khu

vue,

tir doan ke toi b e ,
- l>=X, voi 1 = chieu dai doan ke: X= khoang eachedcbaZYXWVUTSRQPONMLKJIHGFEDC

- X <0 vo: 0= khoang each tir doi s6ng nhao den be.
T6 hop elk dieu kien tren, theo CERC, se darn bao cac doan ke vira phat
huy rac dung lam giam nang lu o n g s6ngXWVUTSRQPONMLKJIHGFEDCBA
ta i vira tao dieu kien d~ cac vat lieu boi
tich c6 kha nang di chuyen toi phia bo de boi tu cho bai.
Trang dieu kien 6 vung yen bien Hai Hau, gia tri L xap xi 23m, 0 >200m

(tirong irng v o i do sau 1,5m va cao s6ng trung binh 0,75m). Vay c6 th~ thoa
man cac dieu kien tren bang each lay khoang each B = 100m.
•

B i e n p h d p RQPONMLKJIHGFEDCBA
c h o n g lu n v a x o i fij c h o n c o n g tr in h

true n e n m6ng khu vue nay va tro n g d ie u k ie n d o n g h rc dai b o
bien, khong th~ ap dung bien phap be dem rang rao, ma bien phap chong hin
chan c6ng trinh tot nhat Ia dung CQCvan vay, tuong nr nhu tnrong hop a Cat Hai.
D ei voi cau

•

T r in h tu x d y d u n g h e th o n g k e

T6 hop ke (rno han va pha s6ng) clau tien se diroc x a y dung a ph an cuoi
dong boi tich doc bo, sau khi phan bai 6 day diroc hinh thanh day dll thi t6 hop
tiep theo se diroc xay dung huang dan ve phia dau cua dong boi tich. Doi voi
vung ven bien Hai Hau, tren dean b a dai khoang 17, 2 km va huang dong boi
tich doc bo nguoc chieu nhau theo mua, c6 th~ x a y dung cac t6 hop ke dau tien
tai ba dean bo: nam Hai Thinh, Hai Trieu va bac Hai Chinh, sau d6 khep kin dan
lien t~ICcac ke cho den phu kin tren roan khu vue bo Hai H~u (hlnh 2). Trhih tu
thuc hien nhu vay nharn dam bao khong ngan nguon vat lieu cho cac ke 6 cuoi
dong boi tich, dong thai rut ngan t h a i gian thi cong he thong, phat huy ngay tac
dung cua he thong trong giai dean d a u ,
D ,! k iln k lt q u d

Khi he thong ke diroc xay dung, bai se hinh thanh va diroc nuoi n6i cao dan.
Nguon cung cap boi tlch cho bai gorn c6 dong doc bo va dong vat chat di chuyen

ngang do s6ng. NhLT vay, c o ban mat cat bai moi hinh thanh se nrong nr nhu a
Cat Hili va hinh thanh a ca hai phia cua ke. Tuy nhien them bai se hinh thanh
cham hen, do doc mar bai thoai hon, c h i khoang 1,5 - Z'', do vat lieu cat a day
min hon. Khi them bai dat duoc be r6ng 20 - 25m thi khi do doan bo nay se dat
diroc trang thai can bang dong, kha nang bao ve de se c6 hieu qua nhat. Su c6
mat cua he thong ke chir T nay cling se han che rat nhieu tac dong cua cac dieu
kien thai tiet bat th iro n g .

191


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KETLUAN
M~c du x6i sat be bien 0 cac dean bo Cat Hai va Hai H~u deu dll dien ra
trong mot thai gian dai va gay nen nhirng hau qua nrong n r nhu: lam mat dat
canh tac, gay nhiem mam, pha huy nha cira, cac cong trinh kien true ... Song
nguyen nhan gay ra sat 10 bo lai diroc th~ hien 0 hai doan bo nay rat khac nhau.
Dean bo Cat Hai dien ra nr nhien, it chiu tac dong cua con ngiroi; do dong tong

hop trieu len bi phan tan boi tich ve hai phia dong va tay rei ra khoi khu vue gay
thieu hut boi tich va x6i sat boo Doan bo Hai Hau chiu su tac dong cua con ngiroi
(de, ke) nhieu h e n ; mot khoi lirong 100 boi tich bi di chuyen ngang phan tan ra
sau va di chuyen d9C xuong phia tay nam d~ di khoi khu vue gay thieu hut boi
tich va x6i sat boo
Nguyen nhan gay ra x6i sat bo bien 0 hai dean bo Cat Hai va Hai Hau khac
nhau nen cac giai phap khoa h9C cong nghe n h a t la giai phap cong trlnh cling
diroc tlrn kiern khac nhau cho phu hop tirng hoan canh. Dac bier giai phap cong
trlnh duoc rim kiern sao cho c6 hieu qua, phu hop cling nhir kha thi nhat trang
dieu kien Viet Nam. D6 la giai phap xay dung ke mo han khep dan tir 2 phia bo'
dao VaG trung tam cho d e a n bo Cat Hai, Hai Phong; va giai phap ke chir T c6 the
xuat phat tlr 3 vi trf ban dau toi khi kin her d e a n bo x6i sat Hai Hau, Nam Dinh.

192


TAl LIEU THAM KHAo
1- CERC (Coastal Engineering
Research Center), 1984. Shore Protection
Manual. Fourth edition. Washington D.C.
2- Nguyen Van Cu va nnk, 1987. Nghien ciru xac dinh nguyen nhan bi~n Ian
vao dao Cat Hai va buoc dau d6 xuat bien phap cong trinh phong chong chu
s a Khoa hQC va Cong nghe Hai Phong.
yell. Bao cao khoa hoc hru tnr taiRQPONMLKJIHGFEDCBA

Ap,

3- Dao Manh Giang, Ton That Vinh va Pham Dang
1993. Luan chtrng
kinh te ky thuat bao ve bo dao Cat Hai. LUll trii taiXWVUTSRQPONMLKJIHGFEDCBA

S a Nong nghiep va
Phat trien Nong than Hai Phong.
4- Gidanov A. M., 1984. Cac phuong phap gia co bo bien va su phat trien bo
ban Hai dirong hoc
bien hien dai. Dia chat bien va dong lire doi boo
cong trinh, Vien han Him khoa hoc Lien Xo (tai lieu tieng Nga).
5- Dinh Van Huy, Tran Dire Thanh va nnk, 2002. Dac tnrng hinh thai - dong
hrc va bien dang bo dao Cat Hai, Hai Phong. Tai nguyen va moi tnrong
bien T IX, NXB KH&KT, Ha NQi, tr. 5- 22.
6- Dinh Van Huy, Tran Dire Thanh va nnk, 2003. Dac tnrng hinh thai - dong
lire va bien dangedcbaZYXWVUTSRQPONMLKJIHGFEDCBA
b o Hai Hau, Nam Dinh. Tai nguyen va moi tnrong bien
T X, NXB KH&KT, Ha NQi, tr. 106- 125.
7- Tran Dire Thanh, Dinh Van Huy va nnk, 1991. Xac dinh nguyen nhan va
lap gia: phap phong chong x6i 16 bo dao Cat Hai tren quan diem dia chat
dong lire. Bao cao d6 tai cap thanh pho, thuoc chuang trinh kinh te bien
Hai Phong. LUll trtr Phan vien Hai duong hoc tai Hai Phong.
8- Thanh TD. et aI, 1992. Current status and cause of erosion in Cat Hai
Island of Haiphong. Proc. Regional Seminar on Environment
Geology.
Hanoi. P. 214 - 219.
9- Tran Dire Thanh, Dinh Van Huy, Tran Dinh Lan va nnk, 1997. Dac diem
bien dang bo va giai phap phong chong x6i 16 bo dao Cat Hai, Hai Phong.
Tai nguyen va moi tnrong bien TIV, NXB KH&KT, Ha NQi, tr. 41- 59.
10- Tran Duc Th~nh, Nguyen Dire C,=",Nguyen Hiiu ce , D6 Dinh Chien va
nnk, 2000. Bao cao tong hop dir an KHCN 5a: "Nghien ciru du bao, phong
chong sat Ia bo bien Bac BQ tir Quang Ninh den Thanh H6a". LULl tnt
Phan vien Hai dirong hoc tai Hai Phong.

Uy

193