(7)
BO
KHOA HQC
VA CONG
NGHE
CHUONG
TRINH
KHCN
CAP NHA
NIIOC
KC
08/06-10
B6
TAI:
"Nghien ciiu afsir khoa li(>c va de xuat cac giai phup
khoa
hoc cdng
nghf hdo diirn sir
on
djiili
va
dp
hen
ciia de
hien
Men
CO
trong
tririrng
hop sting,
trieu cif&ng

CHO CAC MO
HJNH.
Cc quan chu
tri:
TrTOng
Dai hoc
Thuy Igi
Chu nhiem de
tai:
GS.TS. Ngo
Tri
Vieng
Ha
noi,
2010
BO
KHOA
HOC
VA CONG
NGHE
CHlTOfNG
TRINH KHCN
cAP NHA NU'dC
KC 08/06-10
B£TA|:
"Nghien
cuu cffs&khoa hgc
va de
xuat
cdc

THOY
Ug'C,
DAC
D|£M
DjA
KY THUAT
DI^N
HINH
COA
DE
B|£N
02
VONG
TRQNG
D|£M
NGHIEN
CLTU,
LLfA CHQN DI^U KI$N
BIEN CHO CAC MO
HINH
CHU NHElM
BE TAI
CO
QUAN CHU TRI
I)
GS.TS.Ng6 Tri
ViJng
BAN
CHU NHIEM
CHUONG TRINH

7
I.
Mvcdich
7
II.
Phucmg
phap fluic hien
7
in.
Ciu
tnic
cua
bdo
do 7
CHUONG 1. PHAN TtCH,
DANH
GIA
CAC
DANG
K£T
CAU
Dfi
BIEN
DIEN
HINH CUA VUNG TRQNG DIEM NGHIEN
CUU
1
1.1. Khai quit
vi
hi

DIEU KIEN
THUY
LVCTACDONGVAODE
VUNG TRONG DIEM
NGHIEN Cinj
17
2.1.
DJc diSm
ve
diSu
ki$n
thiy
l^c
tac dong vao de
vCmg
biin Nam Dinh
17
2.1.1.
Ch6 dp thuy tri6u 17
2.1.2.
Ch6 do song
gio
18
2.1.3.
Nu6c
dang
20
2.1.4.
ChS d$
dong chay

CAC
DAC
DIEM DJA KY THUAT
xAC
DONG
VAO
DE VUNG TRONG
DIEM NGHlfiN OOU
26
3.1.
M$t
s6 net ve vung
hot
vi
de bien Nam
Djnh vaHa TInh
26
3.1.1.
Bcrbilnvlid6bi&i Nam
Dinh
26
3.1.2.
Bo bien vide bien mUhh
27
3.2.
B4o
cao dia chat de bien Nam Dinh
vi
Ha
Tuih

Hi?n
tr^g
va nguyen nhan hu hong
d6
biln
Ha
Tlhh
40
CHUONG
4.
CAC
VAN
DE
KHOA HOC
CONG
NGHE
TANG CUONG
ON
DJNHDE
43
4.1.
Cac
y^u
to
dnh
hudng den
6n
djnh cua de trong
viing
trpng

cac
phan mem thich
hpp
thudng
sir
d^ng
dl
mo
liinh
hoa bai
toan
tinh
de
45
4.3.3.
Mo hinh
toSn
bai toAn
dS
biln
Nam Djnh
46
4.3.4.
M6 hinh
toan
dS
biln
Ha
Tiiih
48

LU^
VA
Kri;N
NGHJ
64
TAILIEUTHAMKHAO
67
BANG
CHC
GIAI
CAC
CHfj"
VI£T
TAT,
KY
Hlf
u
K^
hlf
u
H
W
b
m,
mi
mi,
m,
h,
K
K.

g/cm3
g/cni3
m
cm/s
m3/s.m
T
%
g/cm^
g/cm^
%
%
%
kG/cm'
cm'/kG
%
T
Vm'
Dai
lirgng
Chieu cao de
Be
rpng
day
de
Bi
r§ng
dinh de
H$
so
mai

v^t
li$u
dip
Trpng
lupng
don vi
ciia
vat
lipu
dap
Trpng lupng
v^t
ligu
gia
c6
Clii6u
day
lop
dit nin
Hg
so tham cua nen
Luu lupng bo xung
tii
mai do mua
xai
trpng do phucmg tien giao thong
Dp im tu nhien
Dung trpng tu
nhiSn
Dung trpng kho

phing nim ngang,
HsD
KD
8D
Ls
Hs
8B
1
Hs
Ls
.
1,
Y>YB
Hs
?
<P
T
G,
Gi
a.
m.
mj
fl
ti
m
m
m
m
m
m

H^s6:11
=
0,0075
d6iv6ib^Iatldian;
TI
= 0,10
d6i
v6i
b^
phmi tren
lit khan,
ph4n
dudi chit mach
Chi^u
cao s6ng
tinh
todn,
l^y
bang
Hsi%
ChiSu
d^i
song
Chi^u dii
c^nh
tim b6
t6ng
thuro phucmg
vuong goc vdi
dudng

trupt (thanh
phan
gay tnrpt)
Trpng lupng
khdi
dat trupt (thanh
phin
ch6ng trupt)
He so mai
d6c
cua de tren
mirc nude
HS
s6 mai
d6c ciia
mat
trugt
dual
m\rc
nude
HS
so ma sat
giOa Idp
gia
c6
vdi
dSt
tiian de
HS
s6

chi^u
6
Hmh. 1-7. ciu
kiSn bS tfing mai
de hiin
Hii
Hau, Nam Dinh bi
an
mon 8
Hinh. 1-8.
6ng
buy chan khay bj mit
6n
dinh do ha thip bai 14
Hmh. 1-9.
H? th6ng
m6 han
thit nghi$m tji
Nam Dinh 15
Hinh.
3-1.
Lat cit
dja
chat
diln hhih d6
bien Nam Dinh 30
Hinh. 3-2. Lat cit dia chit
dik
hinh
dS

dim 41
Hmh. 3-9.
Pha hoai do hoa
16ng 42
Hinh. 3-10. Pha hoai do mit 6n
djjih mai
d6c 42
Hinh.
3-11.
Thim vao mai trong
dS
do
tran
dinh 43
Hinh.
4-1.
Giao dien phan mem CRESS 45
Hinh. 4-2. Mat cit
diin
hinh
dS
bien Nam Dinh 46
Hinh. 4-3. Tinh toan
6n
dinh
d6
Giao Thuy-Mat cat D13+10-Trudng hpp
tinh
thupng luu muc
nude

DANH
MVC
CAC
BANG
BEEU
Bang.
l-I.
H$
s6 on dinh 9
Bang. 1-2. He
sfi phy thu$c vao
hinh
d^g
va
each
lip
d}t
ciu kien 10
Bang, 1-3. Trpng lupng
6n djuh
cua
viSn da
14
Bang. 2-1. So
lipu myc nude thyc
do trong thdi gian 22
nim tij
1970-1991
t?i
cac

co ly chung cua
Idp
Idp
1
31
Bang. 3-5. Chi
ti§u
co ly chung cua
Idp
2 32
sang. 3-6. Chi
tiSu
co
1;^
chung
ciia
Idp 6 32
Bang. 3-7.
cac
th6ng so
cp
ban de Nam Djnh 35
Bang. 3-8.
Toe
dp
hgi
thip dia hinh bai bien d chan de do xoi
Id
35
Bang. 3-9.

1^
cac idp dit de
biSn
Nam
Dinh
55
Bang. 4-7. Chi tiSu co ly chung cua
Idp
dit dip 56
Bang.
4-8.
Chi tieu co
1^
chung
ciia Idp 1
57
Bang. 4-9. Chi
tiSu
co ly chung cua
Idp
2 57
Bang. 4-10. Chi
tiSu
co ly chung cua idp
3
58
MdsAu
I.
Myc dich
Muc dich

dieu kien bien cho
cac
mo hinh toan va mo hinh
vjt
ly.
n.
Phinmg
phap
thyc hi^n
-
Tdng
hpp, ki thira
cac
kit qua
nghi8n cihi
tir trudc din nay trong
ITnh
vyc de biin.
- Phuong phap th6ng ke va phan tich
s5 li$u
thyc do.
- Phuong phap m6 hinh toan, mo hinh vat
1^.
- Phuong phap dieu tra thyc dja.
m.
Cau
triic
ciia
bao cao
Ngoai phin md diu, phin kit

kiSn biSn
dia ky thuat tac dong vao
de vimg trpng diem nghien
ciiu;
Chuong 4
cac
vin di khoa hpc c6ng nghe tang cudng
8n
dinh de
CmrONG
1.
PHAN
TiCH,
DANH
GIA cAC
DANG
K&T CAU BE
BI£N
BEEN
HlNH
CUA
VtfNG
TRQNG
DitM NGHlfeN CUU
l.I.
Khai quat vi
h|
thong de bien Nam Djnh,
Ha TTnh
De

nang cap
de biin
cac
tinh Bic Bp
dupe
chia lam 3 thdi ky: Thdi ky trudc du an PAM 5325 va
PAM4617, thdi ky sau dy
an
PAM 5325 va PAM 4617 va thdi ky sau bao
nam
2005.
Ngoai ra
cac
tuyin de bien
thih Ha
Tinh con
dupe cOmg
c6
nang
cip bdi
cac
dy an khac
nhu
OXFAM,
tuy nhien Do la
cac
m6c thdi gian danh diu sy thay
d6i Idn
vi quan niem
doi vdi de bien

dS
bien: Dupe
bao
v$ bing nhieu hinh
thftc,
nhimg
noi phia trudc de co
rimg cay chin song
tdt
thi mai de chi
trdng
co; nhiSng noi trudc de khong co cay chin
song, mai phia biin thudng xuyen chiu tac dpng
ciia
song thi
dupe
bao ve bang ke lat da
khan, thong thudng la
lat
bing da
h^c
day 30cm tren
Idp
da dam day 10cm. Chan ke bing
lang
try
da
hoc hoac dai da hoc rpng
2T-3m
day 30cm tren

quancii
5
nam
dip mot tuyin mdi
iiii
vao phia trong di thay thi tuyin ngoai.
ThM
ky sau dy an PAM 5325 vi PAM 4617 (Sau nam 2000): Dupe sy tai fro
ciia
Chuong
trinh
luong thyc thi gidi (PAM) dy
an
phyc
hdi
va nang cip de biin cac tmh ven
biin Bic Bp tir Quang Ninh din Ninh Bmh dupe thyc hien tir
1996*2000.
Qua 4 nam
thyc
hiSn,
361.5km
dS
dupe nang cip vdi chi
tiSu
thiit ki la triiu cudng tuong
ilng
vdi
tin suit 5%,
gjp

dudng kinh
Im,
dat sau din mat bai ty
nhiSn
trong
ch6a
diy da hpc. Phia ngoai dupe giiS bing lang thi da, tir dmh chan khay
dSn
cao trinh +3.0
*
+3.5
dupe
lat bing ciu
kipn
be tong day binh quan 0,25m tren idp
da
dam lot day 10cm va
vii
dia ky
thu|it.
Tit cao trinh +3,0m
hoje
+3,5m trd
len
din dmh de
dupe lat bang da lat khan trong khung da xay
hoic
be tong. Mpt so tuyin dinh ke co
tudng chin sdng bing
da

lin
diu
tiSn dS
biin dupe thiit ki cd
h?
thing.
Cao
yiu ti tac dpng nhu
sdng, gio, thuy triiu, nude
dSng
dja hinh, dja chit, hai van, dpng lye hpc biin dupe di
cap di
tfah
toan
cic
thdng s6 co
ban
cua de.
- Day
la
dip cd diiu
ki^n
di
ap
dung
ciia
cdng
ngh$
mdi,
v^t

Mot so van
Se
con ton tai:
- Phin
Idn
cac tuyin de diu
liy
cimg tieu chuin thiit ki va
cac
thong s6 tinh toan
nhu thuy triiu,
nude
dang, hudng va da gio,
- Thiiu tai lieu
co
ban phyc vu tinh toan va phuong phap tinh toan eon han che.
-
Mai
de phia biin
dupe
thiit ki bing m = 4+5
va mai
phia ddng m =
3
la qua doe,
so vdi
dS
biin
ciia cac
nude trong khu vyc va tren thi gidi.

tit),
nen khi sdng
tran
qua
hojc
mua
Idn gSy
xdi
lam
hu hdng de tir trong ra.
- Do
h^
chi vi kinh phi dupe tai trp nen
mai
ke chi lat cau
kiSn
d^n
cao trinh
+3,0ra hoac
+3,50m. De on djnh, cin thiit phii lat din dinh
dS.
- Thiiu thiit bi
va
ti chire do dac quan
trie
biin dpng ciia bai trudc de,
cac
yiu
td
hai van,

tac
dOng
tryc tiip cua sdng
va
bai
trudc de ha thip
mjnh.
ThM
M
sau bao nim
200S;
Nam
2005 vimg biin Bic
B$
chiu anh hudng tryc tiip cua 3 con bao lien tiip: S6
2,
sfl
6 va s6 7 da lam
vd
tuyin de biin Cat Hai (Hai Phong),
m$t
so doan thupc de Giao
Thiiy, de Hai Hau va
d6
Nghia Hung (Nam Djnh), lam hu hdng
n^ng
nhiiu tuyin de
khac.
Ngay sau
bSo,

tuyen de biin dam
bao
ching
gid, bao cip 9 kit hpp triiu tin suit 5%, khu dan cu chong gid, bao cip 12 kit
hop triiu tin suit 5%.
Theo s6
li$u
thing
kS ciia cac
dja phuong, tinh din hit nim 2007,
hi6n
trang de
biin
Nam Djnh,
Hi
Tmh nhu sau:
* Tinh Nam Binh:
Cd 03 tuyin de biin vdi tong chiiu dai
la
90,82km
thuOc
dia
ban
03 huyen
la
Giao
Thuy,
HM H$u
va Nghia Hung. Trong nim 2006, 2007 ciing ci dupe 27,78km de xung
yeu theo tieu chuan trong QD58.

Nghi
LOc.
Nam
2006,2007
da ciing ci dupe
13,03
km, 24km de
xung yiu theo tieu chuin trong QD58.
HiSn
tram
cdc doan
con
lai
chira
dau tu
theo
OB58:
- Mat de:
Chii
yiu cd cao trinh tit +3,50m din +4,50m,
m§t
sd doan cd cao
trmh
chi
tijt+2,0mdin+3,0m.
- Bi
r$ng
mit: Ldn hon 5,0m: 10,97 km; cong
l?i
mat de eon nhd.

H$
thing de biin Nam Djnh
va
Ha
TMi
c6
cac
dang kit ciu bao
ve kha da
d?ng,
t$p
trung vao
m$t
s6 dang sau:
3
1.2.2. Ket cau bao
vf
mdi di
1.2.1.1.
Hi£n
trang
Trudc day, hiu hit mil
dS
chi
bao v$
bing trong cd, chi si it nhimg doan true dien
biin dupe bao
v$
bing
da lat

khdi hiu nhu
khdng
cdn
dupe sii
dyng trong viic
bao vf
mix de biin. Chi chip
nhan
k6t
cau mai
de bing cau kien
bS
tdng
diic
sin ty
ch6n
thanh mang mim.
Hinh.
1-3.
Bao ve mai
bang
cau kien be tong tu
chen
Hinh
thirc
vi
chilu
diy
viln
ciu

ap dung d cong trinh ke Doanh
Chau - Ba Non tren tuyen de bien Hai
Hau,
Nam Dinh tir nam 1994. Day la cong trinh
thir nghiem, cua Vu Phong
chdng IG lut
va
QuanJy
dS diSu (hiSn la
Cue
Quan ly de
diSu
va Phong
chdng
lut
bao).
Qua con bao nam
2005,
cong trinh
van
on dinh.
Hinh.
1-5. Cau kien be tong
Tscl 78
lien ket 3 chieu
- Dang cau kien be tong ngam 01 hoac 02 chieu:
Dupe
ap dung d kha nhieu cong
trinh ca d Nam Dinh va Ha TTnh. Qua can bao nam 2005, hau het cac cau kien dang nay
deu on dinh.

doan de bi
pha hdng
la
tryc
di$n
vdi biin chju
tac
dpng tryc tiip cua sdng ldn. Thyc ti qua
cie trin
bao nam 2005 cho thiy, nhiing
do?n dS
tryc tiip biin, mai phia biin dupe bao ve bing
da
hoc lat khan, da
xiy
tir cao trinh +3,50 trd
ISn
(tit cao trinh +3,50 trd xuing bao
vS
bang
cau
kien be tdng do trudc
day
khdng dd kinh phi diu tu) la khdng dam bao in djnh
ben viing; bao si 7
nam
2005 song ldn da lam hu hdng
ning,
hoac phi buy phin da
lat

dn dinh, ben
canh
do hinh
dgng
tudng
m^t
sd khu vyc
chira
thyc sy phu hpp, khi chiu tac
dpng
true
tiip
ciia
sdng, tudng bi
lat,
hoac
bi be gay din den vd
de.
Day
la
co che vd de da
xiy ra
d Dd
Son
-
Hai Phong.
- Sdng va sdng
leo
cao hon
miic

bing da
lat,
hoac trdng cd)
giy
vd de tit phia trong ra,
Cac hu hdng
Idp bao vi
mai bing ciu ki$n
bS
tdng
diic sin
cd hen kit ciing cd xiy
ra nhung
la
nhiing hu hdng
eye
bO.
Nguyen
nhin
chu yiu la do than dd bi ldn qua
mde
cho phep,
Idp
lpc giiia
thSn d8 va
idp bao ve khdng tit tao
nSn
hi$n tuong xdi ngim
lam
ring than de,

phu
mdi:
Trgng luong toi thieu
eiia
vien da hoac
cau kien lat mai
dupe
xac dinh theo cong
thCtc
Hudson:
'^"M
cot gar
(1-1)
Trong dd:
G:
Trpng lupng vien da hoac cau kien (tan = T).
YB
: Trpng lupng ri^g ciia
cau
kien
(T/m^)
y :
Trpng lupng rieng ciia nude
(T/m^)
a:
Goc
nghidng
cua mai ke so vdi mat phing nim ngang, cotga = m.
HSD:
Chiiu cao sdng thiit ki (m).

l^p
Ty chen thanh
ming
KD
3
4
3,5
5 + 6(*)
(*) Cdn
kiem
tra gid tri
th{cc
te doi vdi
titng logi
mdng.
Chiiu
day
yeu cau cua
khoi
phu mdi:
+ Ldp phii mai bing da hpc lat khan: Khi 1,5
£
m < 5 thi
d$
day in dinh tmh theo
cdng thiic:
So
=0.266-
H,
(1-2)

Chiiu day tim
ban
be tong (m);
(1-3)
r|:
H§
si
t)
=
0,0075
dii vdi ban lat khan;
T|
= 0,10 ddi vdi ban phin
trdn lat
khan, phin dudi chit
mach;
Hs:
Chiiu cao sdng tinh toan
(m),
liy bing
Hsi%;
Ls:
Chieu
dai
song (m);
It:
Chi^u
dai canh tim bS tong thuo
phuong
vuong goc vdi dudng

f
= -
(1-5)
(p:
He
s6
phu
thu^c vio
hinh dang va
each
lap dat
cdu
kiSn, lay theo bang:
Bang.
1-2.
H$ so
phu
thuQC
vao hinh dang vd cdch lap dat
cau
kien
Loai va
c&ch
lap
d^t
cau
ki^n
Tam lat dat nam
Tam
lat

G; 6n dinh
tru0
theo
mgt
day cong
trinh
gia co
her co
the dan gian hod
thanh
truat
tdng thi
theo mgtphang
gay khuc)
Cdng
thdc
tinh
h§
si in dinh
ciia
khii trupt:
Gj-sinoTj + Gj-cosoTaJgaj +Pj.sin(a2 +a^)ig<p
"
i',.cos(a,
+«3) (1-6)
10
Pj =Gj.sinaj
-Gj.cosa^Jgip-
Ct
-Pi.cos(a|-a2)

gia ci: Khii gia ci vi than de la
vat li$u
cd cudng
d0
ching cat khac nhau, khi myc nude thip thudng
xay
ra trupt theo
mat
tiip
xdc
cd
cudng dp chong cat
yeu.
Phuong trinh on djnh
(1-10)
•
(1-11)
(1-12)
Trong do:
mi:
He s6 mdi d6c
ciia dS
trSn
m\rc
nude;
m2:
HS s6 mai
d6c ciia
mat truot dudi muc
nude;

-I-
Tinh
6n
dinh ldp gia c6 bd khi c6
sii
dyng vai
loc
dia ky thuat (geotextile):
G,
< / Gj
hoac
^ = tga<
F^
Gj
Thuc te dp
diing
- Chpn he s6 mdi: Thudng
idy
theo
h$
s6
mdi
de
hi^n
cd hoac cac doan tuong tu da
lam,
h$
s6 mai m =
3 -^
4.

tir
bao s6 2, sd 7
nam
2005 ed
thS
khang
dinh cac
cau
kien be tdng
bao
v^
mai
ngoii
da lam trudc day la on djnh, da lat khan va da
xay
khdng dn dinh. Vi
v$y,
toan bp
cac hh
so thiit
kl
ciing
c6,
nang
cip de biSn
dSu
chpn
ldp gia cd bao ve mai phia
biin bang
ciu

bai.
- Tinh ldp gia co bao ve mai:
Tinh
toan dd theo 03 cong
thiic
da neu trong Tieu
chuan. Tuy nhien khi tinh chiSu day ldp phu theo cdng thiic
ciia
quy
pham
Trung Quoc
va cdng thiic Pilarczyk,
K.W
cd
sir chenh Ifeh
ldn. Nguyen nhan do ket qua
tinh
chieu
cao sdng
Hsi%
va
Hsi/3
va
Ls
khong chuin.
- Tinh on dinh mai:
Hau
hSt cac Tu vin bd qua tinh on dinh
nSi
bd ldp gia c6, chi

cd hS sd mdi m
^
3, dit dip than
dS
co gdc ma sdt trong tuong
ddi ldn nen
kit
qud tinh todn
6n
dinh trupt t6ng
thi
va
6n
dinh ndi bp ldp gia c6 diu vupt
ySu ciu. Tuy nhien, viSc chpn hS sd mdi
dS
bien con quyit dinh
din
chieu cao de va quy
md ldp
gia
cd
bdo
ve mdi (qua cdc cong thuc tinh co the nhan xet chiiu cao song
leo
vd
trgng
lugmg.
chiiu day lap phu mdi ty
le nghjch

trong
TiSu
chuin.
Doi vdi cau
ki^n
be tdng dung bdo
v?
mdi de
biin,
vdn dS
quan trpng
Id
chieu day,
trpng lupng cua ciu
ki?n
va mac bS tdng, khdng phu
thu^c
nhiSu vao hinh dang. Do vay
nen chpn mpt sd
lo^i cdu
kiSn don gian, dl thi cdng, cd
thi
dp dung thi cdng
ea
gidi de
dua vao Tieu chuin, xdc djnh cdc
h?
sd thuc nghiem, tiSn tdi chuan hoa tao
thudn Ipi
cho

biin,
chieu
cao sdng (Hs) va chiSu day ldp
phii
mai. Cd hai loai chan khay la chan khay nong va
chdn khay
sau:
- Chan khay ndng: Ap dung cho viing cd
miic d6 xdm
thyc it, chan khay chi chdng
do dong chdy do sdng tao ra d chdn de, chan khay kSt
cau
bang dd
hSc
xIp,
cd cdc hinh
thdc:
D^g
thSm phu cao;
Dang
thIm
chdn trong dit;
Dang md nhd.
- Chdn khay
sdu:
ap dyng cho vung bai bien bi
xam
thuc manh. Chan khay
sau
cim xudng khdng nhd hon 1,0m. Thudng

Dupe
dp dung phd
biin
d
nhOng
khu vyc it chiu tac ddng cua sdng nhu viing
ciia
sdng,
viing
cd cay chdn
song phat trien
t6t,
viing
biin
boi,
13
- Chan khay
sau
dang ong buy
diic sin
bing
b&
tong ed chiiu cao khoang 2,0m
chdn,sau
xuong mit bai,
ap
dyng d
nhthig
khu vyc biin tiin, bai khdng on dinh bii xdi
theo mua,

h?
thip bai. Din nay tai nhieu khu
vyc ong buy chan khay da bj nil len khdi
mjt
bai, nhiiu cho nhd len khdi mit bai tdi
0,50m, nguy co sap di rit cao.
Hinh.
IS. Ong
buy chdn
khay bi mdt 6n dinh do ha
thdp
bai
b)
vi
mat ly thuyit: Khi thiit ki chan khay de biin, Tieu chuin thiit ki da hudng
din chi tiet
vipc
on dinh
vidn vit liSu va
kha nang xdi
sau
tai
vj
tri chin khay.
- Tinh toan kich thudc da
lim
chin khay:
Ydu
ciu: in dinh dudi tac dyng ciia dong chiy do sdng tao ra d chin de.
Trpng lupng in dinh ciia vien da

cdn qua chung chung. Cin dua tieu chi dl xdc dinh ro
miic
d^
xdm
thyc bai it va
miic
do
xam
thyc bai nhiiu.
- Mdi hudng dan tinh trpng lupng viSn da tai chdn de, tuy nhiSn thuc
tl
kh6 co the
tim
dupe
dd cd kich thudc va trpng lupng theo yeu ciu.
- Mdi chi c6 quy dinh chan khay sau phdi chdn
xuIng
khdng it hon 1,0m, chua co
hudng din tinh todn chilu sau chdn khay cin thiit.
Vi?c
dp dung chan khay
sau
d6i vdi
nhOng
khu vuc
biin
tiin,
bai
biin
thudng

nudi bai bang tau
hiit
cat.
Qua thuc tl bao sd 7 ndm 2005 cho thiy
rimg
cay chdn sdng phia
biin
dong vai tro
bao '/S
de
biin hit siic
quan trpng nhd cd
cay
chan sdng, cho nen de Binh Minh (Ninh
Binh) toan bd de Thai Binh va nhieu doan
ciia
de Nam Djnh ngay tai de Hdi Hau do cd
thi
khang dinh cd doan chua
dupe
lam ke kien cd nhung cd bai cd
cay
van dn dinh.
HiSn dpc bd biSn Nam Dinh, d khu vyc bien tien manh da
dupe
thi diem xay dung
hS
Ihdng
md han
gdy

dii dh
ddm bdo In
dinh khi chiu tac ddng cua sdng.
+ Md han
bing
dng vdi dja
kj^
thu$t
kem on dinh do cong
ngh^
lien
kit
va bien
phap thi cdng chua phu hpp.
-I-
Nudi bai la
biSn
phdp
tit,
vira
rS
tiin vira
phu hpp vdi moi trudng sinh thai dang
dupe dp dung nhiSu tren the gidi.
6 nude
ta
vi^c
dp dyng cdn kho
khdn
do thiiu trang

tieu chuan thiSt
kS dS
bien phdi tren eo sd va tam quan trpng cua khu vyc dupe de bao ve,
tir tir
cdc yeu td tac dpng cua
timg
vung, tung tuySn ma cd
thi
cd tieu chuin cho timg
vung,
tCmg
tuyen khac nhau.
Mudn
vdy,
cong tac dieu tra co ban phdi
dupe
quan tam dung muc, nhdt la diSu tra
cdc thdng sd ve thuy trieu, sdng, gid, dong ven,
diin biin
bd, bai va tinh hinh kinh te - xa
hdi de phyc vy cho vice hoach dinh qui md va
mijrc
dp nang cap he th6ng de bien phu
hpp.
Cd
thi
khdng
dinh
de bien noi chung va dS
Bac

hi dpng. Doi vdi de, cin co bien
phdp bao vS mdi phia
ding
thich hpp de chdng xoi mon do
nude
mua va do song tran qua
dS.
16