I KHOA HOC l B , J . 1 5 [ e | g ! t i ! T ^
^ PHAN TICH, DANH GIA HIEU QUA MOT SO CUM CONG TRINH MO HAN TREN HE T H O N G SONG VUNG
D O N G BANG BAC BO
TS. Nguyen Kien Quyet Trudng Dai hgc Cdng nghe Giao thong van tdi
Tom tat: Tren cdc he thdng sdng viing Ddng bdng Bdc Bd (DBBB), cdng trinh tdc dgng vao dong chdy chu yiu Id md han (MH), dgc biet tren he thdng sdng Hdng cd tdi hang tram MH dugc xdy dung tren cd bd td vd bd hOu. Cdc cdng trinh phdn nao phdt huy hieu qud, nhimg vdn cdn mgt sd tdn tai Trong noi dung bdi bdo, tdc gid di sdu phdn tich nhirng han chi vd tdn tai d mgt s6 cum c6ng trinh MH dien hinh. nhdm rut ra bdi hgc kinh nghiem trong linh vuc chinh tri sdng bdng cdng trinh tdc dgng vao dong chdy d nude la.
Tdkhoa: Sat l&b& sdng, mo ban, hieu qua cdng trinh md han, giao thong van tai thiiy, bao veb&song.
Summary: In Northern River Delta system, works act on major flows to be spur dike, special in Red River system have many spur dike M'as built in either right or left Red River bank Built works have little effect, and also have some remains. In contents of paper, author only analyses limitations and existences in some spur dike works system, to promote withdraw experiences in river training field by works act onflows in Vietnam.
Key words: Erode river bank, spur dike, spur dike works effect, navigation transportation, protect river bank.
1. DAT VAN DE
Trong nhiem vu phdng, chdng va giam nhe thien tai d Viet Nam, xay dung cdng trinh bao v? bd sdng ludn la h^ng myc hang dau. Thdng thudng, logi cdng trinh phd bien, dem gian, dugc ling dung lau ddi la ke gia cd bd vdi cac ket ciu khac nhau, tiiy theo dieu kien kinh te, ky thuat mdi noi. Ke gia cd bd la loai cdng trinh bi ddng, dimg vat lieu cd tinh nang chdng xdi tdt true tidp phii len bd dat can bao V?, khdng tac ddng vao nguyen nhan gay sat Id la ddng chay. Tir nhiing nam 70 cua thd ky XX, d Viet Nam bat dku img dung loai cong trinh chu ddng, tac ddng vao ddng chay day chu luu ra xa bd de loai trir nguyen nhan gay
Ngudi phan bien: PGS.TS Pham Dinh Ngay nh^n bai: 04/5/2015 Ngay thong qua phan bi?n: 22/5/2015 Ngay duy?t dang : 05/6/2015
sat Id bd, dd la md han. Tit trudc den nay, md han ed ket cau phd bien nhat la khdi dd hinh niii, thdng thudng la da hoc, rg da hoac khdi be tdng, dac biet la tren cac sdng cua he thdng sdng Hdng. Loai cdng trinh nay dugc phat tridn lien tuc va rdng khap, thu dugc nhung hieu qua dang khich le. Nhihig md han xay dung tir nhiing nam 1970, 1971 den nay van tdn tai, nhirng md han dang vk se dugc xay dung ngay cang nhieu, chiing td nhirng hieu qua tich cue ma nd mang lai. Nhung sd lugng cac doan sat Id ngay cang tang trdn cac trien sdng, ben canh nhiing doan sat Id mdi van tdn tai nhihig doan sat Id da cd tir 30-r40 nSm nay. Hien tugng dd mdt phan nao ndi len su han c h i trong hieu qua chdng sat Id cua cac cdng trinh da xay dung. Trong ndi dung bai bao, tac gia chi di sau phan tich nhirng han c h i va tdn tai d mgt sd cum cdng trinh MH diln hinh, nhSm nit ra bai hgc kinh nghiem
TAP CHIKHOAHQCVACONGNGHETHOY LOI S6 27-2015 71
I KHOA HOC ^ E S B I B i I ^ trong ITnh vuc chinh tri sdng bang cdng trinh tac dgng vao ddng chay d nuoc ta.
2. PHAN TICK, DANH GIA HIEU QUA KY THUAT CUA M O T SO CyM CONG TRINH MO HAN TREN HE T H 6 N G S 6 N G V U N G DBBB
2.1. Co sd de danh giS hieu qua ky thuat ciiaMH
Hieu qua ky thuat cua cdng trinh MH dugc danh gia thdng qua do an toan cua dudng bd dugc bao ve va su dn djnh ve kdt cau ciia ban than MH.
- Do an toan cua dudng bd dugc bao ve lai dugc bao dam thdng qua kich thudc ciia khu nude vat (KNV) ma MH tao ra, trong do do dai KNV cd vai tro chii dao. Kich thudc KNV cang lon, hieu qua bao ve bd cang cao.
- Su dn dinh ciia ban than cdng trinh MH lai phu thudc vao kich thudc hd xdi cue bd dau miii MH, trong dd dg sau ddng vai trd quan trgng. Do sau hd xdi lai quylt dinh true tiep bdi luu tdc ddng chay (hoac gian tiep la ket cau ddng chay) diu mui MH, ndi mdt each khac la dd chenh giQa luu tdc ddng chay va luu tdc khdi ddng cua
biin eat long din dau mui MH.
2.2. Cac cym mo han tai khu vm: hgp liru Viet Tri
2.2.1. He thdng c6ng trinh chinh tri da xay d^g a) Cym MH C6 Dd, [1], [2], [3]
- He thdng cdng trinh Cd Dd la tdn ggi chung cua 3 cdng trinh: Cd Dd, Vien Chu va Phii Cudng bao vd cho de hiru sdng Hdng, vi tri tir K5dlnK10+100dai5km.
- Bat diu xay dung tit nam 1954 vdi quy md lat mai d nhiing doan bd sdng hi xdi Id ngay sat chan de, dan dan do pham vi sat Id lan rdng lan rdng ke dugc ndi lien tuydn tii Cd Dd tdi Phii Cudng. Nhihig nam tir nam 1958 den 1960, nhung chd sgt Id manh da xii ly bang rdng da hd chan va tha c\im cay gay bdi va tu nam 1982 bat dau xay dung MH dl hudng ddng chay chinh ra xa bd, han chi sat Id bd. Qua qua trinh vira xay dung them MH mdi, tu bd MH cfi, cho ddn nay da cd he thdng 19 MH.
- Thdng ke he thdng MH d Cd Dd hien cd nhu sau (theo thit tu tir thugng luu vd ha luu) bang 1.
Bang 1. Thong ke he thong MH Co Do
Chis6
MHO MHl MH2 MH3 Nffl4 MH5 MH5b MH6 MH7
Vitri
K5-H0
K6-I-900 Nam
xay dimg 1989 1974 1974 1977 1978 1977 1989 1978 1978
Khoang each (m)
200 80 280 210 210 160 170 270
Dai (m)
10 12 14 16 18 20 18 20
Kich thirac cong CTdinh
(m)
-1-14,5 -1-14,5 -1-14,0 -1-14,0 -1-14,0 -H4,0 -1-14,0
•1-14,0 Dinh
(m) 2 2 2 2 2 2 2 2 2
trinh Chan ( m )
-M,0 +4,0 -1-3,0 -1-8,0
•K),0 +3,0 +1,5 -1,0
Goc
75" 75" 75" 75" 75" 75" 75" 75°
72 TAP CHl KHOA HOC VA C O N G N G H E T H O Y L O I S<5 27 - 2015
I KHOA HOC
Chis6 MH8 MH9 MHIO M H l l MH12 MH13 MHM MH15 MH16 MH17
Vitri K7+300
K9+80
K9+620 Nam
xay dung 1978 1979 1979 1979 1972 1972 1972 1980 1980 1980
Khoang each (m) 400 170 250 241
200 150 200 200
Dai (m) 20 13 13 13 13 20 22 20 17 20
Kieh thuoc cong CTdinh
+14,0 +12,5 +12,5 +12,5 +12,5 +10,5 +10,5.
+11,0 +11,0 +11,0
. Dinh (m)
2 2 2 2 2 2 2 2 2 2
trinh Chan (m)
-3,0 -0,2 -0,1 +1,0 +1,5 +2,0 +1,0 +1,5 +1,5 +3,6
G6e 75"
75°
75°
75°
75"
75"
70"
70"
70"
70"
b) Cum MH Le Tinh, [1], [2], [3]
- Nhi?m vu cua he thdng cdng trinh nay la bao ve de ta sdng Hdng thugc huyen Phong Chau, tinh Phii Tho.
- Vi tri: tir K46+800 den K48+100, dai 1.3km, dugc xay dung tir nam 1950. Liic dau, chi cd ke gia cd bd, mai ke sat chan de. Do tac ddng qua lai cua ddng chay vimg hgp luu sdng Da
Bang 2. Thong kS he thong MH Le Tinh
va sdng Thao, k l tir nam 1954 din 1972 thudng xuyen phai xii ly bing rdng da gifi chan va tha cum cay vao cae hd xdi, ke van khdng dn dinh. Tir nam 1973 din nam 1977 xay dung thanh he thdng 7 MH.
- Thdng ke he thdng MH d Ld Tinh the hien trong bang 2.
Chi so
1 2 3 4 5 6 7
Vitri
48+300 48+380 48+550 48+800 49+00 49+200 49+400
Nam xay dung 1973 1973 1974 1975 1976 1977 1978
Khoang each (m)
80 130 250 200 200 200
Kich thuoc cong trinh Dai
(m) 20 20 20 25 25 25 25
CT dinh(m)
+12,35 +12,35 +12,47 +11,80 +12,00 +12,00 +11,80
Dinh (m)
2 2 2 2 2 2 2
Chan (m) +2,0 +0,5 +1,5 +5,0 +5,0 +5,0 +5,0
Goc
70°
70"
70°
70°
70"
70°
70°
TAP CHl KHOA HOC VA CONG NGHE T H C I Y LOI S(3 27 - 201S 73
c) Cum UH Bai Binh, [1], [2], [3] xay drag tit nam 1977 dSn nam 1982 thi hoan - Nhiem vu cua he th6ng cong trinh nay la bao * ^ ™ ^St cju bSng da tha & rp t h ^ hjc m&
ve bo ta song H5ng thuoc huyen Vinh Tucmg, ™ ^"••'^c tu sua vao cae nam 1995,1996.
tinh VTnh Phuc. - Thong ke he thdng MH a Dai Djnh thS hien - Vi tri: Tit K2+068 + K4+<)70 dai 2km, duoc *™S bang 3.
Bang 3. Thong ke he thong MH cimg Dai Dinh Chi
s6 1 2 3 4 5
Vitri K2+450 K2+840 K3+450 K3+700 K3+900
Nam xay dung
1977 1978 1979 1980 1981
Khoang each (m) 390 610 250 200
Kich thuoc cong trinh Dai
(m) 50 48 47 40 38
CTdinh (m) +11.25 +11.20 +11.15 +10.50 +10.10
Dinh (m) 2 3 2 2 2
Chan (m) +4.50 +3.00 +2.50 +2.00 +2.35
Goc 70"
70"
70°
70°
70"
2.2.2. Ddnh gid hi?u qud cdng trinh a) Hi^u qua cdng trinh
Tuy da dugc quan tam xay dung cdng trinh tir rat sdm, nhung hon 30 nam qua, doan hgp luu Viet Tri van ludn la vi tri xung ydu, hang nam deu phai tSp trung nhan lire, vat luc cung cd, hd de, den nay van cdn la 1 de tai nghidn ciiu cap nha nude, do he thdng de van chua bao dam an toan, bd sdng van xdi Id, chu luu van tiep t\ic dao ddng.
b) Phdn tich nguyen nhan han che hieu qua cdng trinh
- Thieu quy hoach tdng the:
+ Vimg nghidn ciiu thudc dia gidi 3 tinh Phii Tho, Vinh Phiic, Ha Tay, cdng trinh de dieu, chinh tn sdng deu do cac Sd dgc lap tien hanh, chua cd 1 quy hoach tdng thd cho toan vimg, cd s\r dieu hanh thdng nhat tir Trung uong.
+ Nhieu vi tri cd tmh khdng chi chua dugc bd tri cdng trinh, nhu miii dat giua sdng Thao va sdng Da, doan bd lom Bach Hac vimg ciia sdng Ld, thugng luu Dai Dinh.
-I- Theo nhu tac gia suu tim, hien nay ve quy hoach tdng thd tuyen chinh tri la chua cd quy hoach tdng the nao da dugc phd duy?t cho t o ^ bg sdng Hdng.
- Bo tri cong trinh khong diing quy cdch:
+ Khoang each gjua cac MH qua Idn so vdi tri sd cho phep bang 4 dudi day chi don cii mgt so trudng hgp trong hai he thdng MH Cd Dd va Ld Tinh.
+ Khoang each qua thua lam cho doan bd giiia cac MH vin tiep tuc bj xdi, hieu qua tao dudng bd an toan khdng thuc hien dugc.
- Cao trinh MH thdp Hon cao trinh muc nude tao long: Cao trinh thap lam cho MH khdng cd tac d\mg khdng che dugc m\rc nude lii cd vSn tdc lon, ddng chay lii va sdng v§n ap sat vao chan de gay nguy hiem sat Id.
- Chiiu ddi MH qud ngin: Hau hit cac MH chi dai khoang (10-i-20)m, lam cho chidu rgng ldng sdng van cdn qua lon, khoang 1200m, trong liic yeu cau chieu rgng chi khoang 800m.
Vl vay, it nhdt, chiiu dai tit ca MH d Cd Dd va Le Tinh phai keo dai them 50m niia.
74 TAP CHl KHOA HQC VA C O N G N G H E T H O Y LOl 5(5 27 - 2015
KHOA HOC Bang 4. So sanh khoang each MH thuc te va ySu cau Thir
tu
1
2
V i t r i
C d D o (b616i)
LSTinh (bo lam)
MH 0+1 1*2 2-r3 3+4 4+5 6+7 1*2 2-^3 3+4 4+5 5+6
Khoang each ^ , Thirc te Chieu dai MH
200/10 = 20 80/12 = 6,7 280/14 = 20 210/16 = 13 210/18 = 11,6 270/18 = 15
80/20 = 4 130/20 = 7,5 250/20 = 12,5 200/25 = 8 200/25 = 8
Khoang each Chi6u dai MH 4+5 4-^5 4-^5 4+5 4-^5 4-i-5 2-i-3 2+3 2-^3 2-5-3 2+3
Yen can
Bang 5. So sanh cao trinh dinh MH thuc te va ySu cau
Vitri
C6 Do
Le Tinh
MH M9 MIO M i l M12 M13 M14 M15 M16 M17 M l M2 M3 M4 M5 M6 M7
Cao trinh dinh thuc te Zi (m)
+12,5 +12,5 +12,5 +12,5 +10,5 +10,5 +11,0 +11,0 +11,0 +12,35 +12,35 +12,47 +11,80 +12,00 +12,00 +11,80
Cao trinh dinh yeu cau Z2 (m)
+14,50 +14,50 +14,50 +14,50 +14,50 +14,50 +14,50 +14,50 +14,50 +15,00 +15,00 +15,00 +15,00 +15,00 +15,00 +15,00
AZ = Z 2 - Z | (m) 2,0 2,0 2,0 2,0 4,0 4,0 3,5 3,5 3,5 2,65 2,65 2,53 3,20 3,00 3,00 3,20
TAP CHl KHOA HQC VA CONG N G H t T H C Y LOI S(3 27 • 2015 75
KHOA HOC ~ ^ E g 3 ! B ! l M i
2.3. Cum mo han tai khu vyc bai Tam Xa, - Cong trinh ch6ng sat 16 ba gflm 15 MH CQC s6ng Hong - Ha Noi be tong c6t thep xay dung tai khu vuc Tam X4, 23.1 Bd tri cdng trinh, [I], [2], [3J duoc xay dung tir nam 1994+1996 xem thdng
trong bang 6.
Bang 6. He thing MH xay dimg tai bai T^im Xa (bof ta song Hong)
S5 TT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Ten cong trinh KTl KT2 KT3 KT4 KT5 KT6 KT7 KT8 KT9 KTIO KTU KT12 KTU KTl 4 KTl 5
Nam XD 1994 1994 1994 1994 1994 1994 1995 1995 1996 1995 1995 1996 1996 1996 1996
ChiSu dai (m)
88 106 117 114 101 114 80 80 75 60 75 65 50 50 50
Cao do dau ke (m)
+7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0 +7,0
Khoang each (m)
206 205 245 200 211 190 200 197 165 195 182 200 210 190
Hinh thirc ket cau Coc BTCT CO phen che Coc BTCT CO phen che Cpc BTCT CO phen che Cpc BTCT c6 phen che Cgc BTCT co phen che Cpc BTCT c6 phen che Cpc BTCT CO phen che Cpc BTCT c6 ph6n che Cpc BTCT CO phen che Cpc BTCT CO ph6n che Cpc BTCT CO phen che Cpc BTCT c6 phen che Cpc BTCT cd phSn che Cpc BTCT CO phen che Cpc BTCT CO phen che 2.3.2. Hieu qua cdng trinh
H| thdng cdng trinh nay dugc xay dung vdi myc tidu chdng sat Id bd bai Tam Xa, dn dinh ludng lach giao thdng thuy di theo tuydn ludng thiet ke (L^ch trai). Cdng trinh nay ban dau cd phdn che kin tir dinh MH den chan, cd tac d\mg can ddng gay bdi. Cdng trinh dugc bd tri
mat bang theo diing cac chi dan ve chiiu dai va khoang each giiJa cac MH, giai doan d^u dS phat huy dugc hieu qua nhdt dinh. Sau mgt thdi gian phen che bi hu hdng, MH trd thanh loai ket cau cd nude xuyen qua, kit cau ddng chay phuc tap. Thdi ky miia nude lon, khi ddng chay lu d-an qua, tao ra cac xoay true diing va true ngang, bd sdng ha luu cac MH
76 TAP CHl KHOA HOC VA CONG NGHE T H O Y LOl S(5 27 - 2015
KHOAHOf: M-i'll'infMil-M
ddu bi xdi sau, diln hinh la khu vuc giiia KT13 va KTl4, xdi sau din cao trinh -17m (hinh 1, 2
va 3). Xet ve hieu qua kf thuat la chdng sat Id va on dinh ludng tau thi cdn han che.
Hinh 1. Sat Id goc MHKT14 Hinh 2. Khu virc xdi sdu giira hai MHKT14 vd KTl 3
Hinh 3. Hd xdi hg luu MH KT13 2.3.3. Phdn tich nguyen nhan
' He thdng cdng trinh 15 MH TSm Xa dugc xay dung vdi muc tieu chdng sEit Id bd bai Tam Xa, dn dinh ludng lach giao thdng thuy di theo tuyin ludng thiit kl (Lach trai). Cdng trinh nay ban dau cd phdn che kin tir dinh MH din chan, cd tac dung can ddng gay bdi. Cdng trinh dugc bd tri mat bang theo diing cac chi dSn ve chieu dai va khoang each giua cac MH, giai doan dau da phat huy dugc hieu qua nhat dinh. Sau mdt thdi gian phen che bi hu hdng, MH trd thanh loai ket cau cd nude xuyen qua, ket cau ddng chay phiic tap.
Thdi ky mua nude Idn, khi ddng chay lu tran qua, tao ra cac xoay true diing va true ngang, bd sdng ha luu cac MH ddu bi xdi sau, dien hinh la khu vuc giiia KT13 va KT14, xdi sau den cao trinh -17m . Xet vd hi?u qua ky thuat la chdng sat Id va dn dinh ludng tau thi cdn ban chd.
- Hien tugng xuat hien hd xdi sau ha luu gdc MH la hien tugng kha phd bien tai cac cum MH tren sdng Hdng, cac cum MH chinh tri ludng lach giao thdng thuy tren sdng Dudng.
Dieu nay dS han che kha Idn den hieu qua bao ve bd chdng sat 16, tham chi gay ra nhiing hau qua nghidm trgng hon trong dilu kien tu nhien. Thdng qua nhOng phan tich ta Xhiy:
+ Hien tugng xdi bat thudng dien ra hau hit d cac cum MH bd tri tren cac doan cong gap, mui MH khdng cd mdc ngang theo chiiu ddng chay dd han chd anh hudng ciia hoan luu sdng
cong. Ddng chay phuong ngang cd phuong tning vdi true MH, tdng hgp vdi hoan luu true ngang sau MH tao ra ket cau ddng chay phirc tap va cudng do rdi dgng lon, dan ddn xdi Id bd cdng vdi xdi Id day lam cho hd xdi vita sau vira rdng nhu da xay ra.
-I- Hau het cac MH diu cd cao trinh dinh MH thap, ddng chay tran dinh cd do sau Idn, MH lam viec nhu mgt dap tran, tang thdm quy md cua hd xdi cue bd.
+ Hau het cac trudng hgp da dan deu cd vung bai rdng va cao, khi ddng lii nit tir bai xudng gap bd cao, ddng chay bidn ddi dot nggt ciing gay ra sat Id bd.
-I- Anh hudng cua mai ddc bd cung la ydu td can quan tam, mai bd trong cac trudng hgp nghien ciiu deu rat ddc, gan nhu thang diing.
2.4. Cum Phil Gia - Tu Lien, song Hong - Ha No!
2.4.1. Bd tri c6ng trinh, [IJ, [2], [3]
- Cum cdng trinh Phii Gia - Tii Lidn (hinh 4 va thong ke trong bang 7) nlm trong he thdng cung trinh dn dinh ludng lach chay tau doan qua Ha Ndi, nhung dugc xay dung sau khi do dua dugc ddng chu luu ve thiiy vuc cang Ha Ndi. Nd CO nhiem vu han che luu lugng vao lach Quyt, lach Phii Gia, tang luu lugng cho lach TSm Xa va lach Gia Lam, theo the sdng A dd lira chgn lam tuyen chinh tri.
TAP CH( KHOA HOC VA C O N G N G H E T H O Y LOl SO 27 - 2015 77
Bang 7. Cac tham so Hf thSng MH Phii Gia - Tir Lien
sa
TT 1 2 3 4
Ten cum cong trinh va cong trinh Kl -Phu Gia K2 -Phii Gia K3 -Phii Gia K4-Tii Lien
Nam xay dimg 1996 92+93 93+98 95-^98
Chieu dai (m) 300 320 510 255
Cao dp ra) +5,5 +5,0 +5,0 +6,0
Hipn trgng bi lap hu^hong hu hong nSng binh thudng - Cum cong trinh Phu Gia - Tir Lien da co tac chay tran qua gay sat sut cong trinh va lam sat d\ing nhat dinh trong viec ban che dong chay la doan ba lach Quyt khu v\rc x3 Tu Lien, ph^i song Hong vao lach Quyt, nhimg do cao trinh cap toe xSy dung mpt tuang dpc ch6ng sgt 16 dinh cac MH dat 6 cao trinh thap, miia lu dong (hinh 6).
Hinh 4. Cum cdng trinh Phu Gia- Tu Lien - sdng Hdng
Hinh 5. K3 dirt thanh 3 doan Hinh 6. Ddp doc Tic Lien
2.4.2. Hifu qud cum cdng trinh Phu Gia - TuLien
HiSn nay, trir MH K4 diu bai Tir Lien, cac MH con l?i dSu bj hu hong. Cong trinh huong dong chii l^c K3 tren mat bing co hinh chii r, dai t5ng cpng 510m, da bi diit thanh 3 khiic each xa nhau nhu trong hinh 5 the hien. Noi day, cong trinh hu hong tao ra cac bai da nhap nho, ngon ngang giOa vimg song nuoc voi nhieu c6n lach phan tan, giira um tiim lau say, da tro thanh dijm vui chai da ngoai hip dan cho cac b ^ tre, va dang tiic la da xiy ra vai vu chet duoi do say chan xu6ng cac h6 sau quanh khu vuc.
2.4.3. Phdn tich nguyen nhan
• Hien tupng dien bien phirc tap khong nhu y
tai doan Phii Gia - Tii Lien co thi giai thich thong qua ca ch6 dong chay mo ta trong hinh 7. Y d6 cua nha thiSt ki la tang cuong luu lupng cha lach trai de cai thi^n diSu ki$n chay tau trong mua ki?t, nen cong trinh huong dong tvr bcr trai huong sang ba phai dupe thiit ki vcri cao trinh dinh thip, +5,0m iin +6,0m, CO chieu dai vuon ra den bien tuyin chinh tri.
Nhimg chinh cao trinh dinh cong trinh thip da bien cong trinh lam viec trong miia nuac cao thanh dang mo han ngim, khong huong dupe dong chu luu sang phia bo Gia Lam nhu y mu5n ma ngupc lai, huong dong chay m^t voi (van tic lon) dua vi phia Ijeh Quyt \i theo quy luat hoan luu, dong chay day (mang nhiiu biin catO s6 chuyin sang huong ngupc lai, di vi phia lach Gia LSm, gay hien tupng
78 TAP CHl KHOA HOC VA CONG NGHE T H O Y LOI S(3 27 • 2015
KHOA HOC M E ! 3 ! S ! I ^ B phan tac dung nhu da ndu d tren. Den mua
nude kiet, cdng trinh phat huy tac dung, hudng ddng chay mat sang bd Gia Lam va ddng chay day vl phia lach Quyt nhung liic nay ddng chay mua kidt khdng manh, khdng du siic xdi di nhiing vimg bdi da dugc tsio nen trong miia nude cao, chi gay bdi bai d khu vuc gdc ke vdi cao trinh bai tuong ddi thap.
B O N Q C H A Y S O N G H d N O
Hinh 7. Phdn tich ket cau ddng chdy tai khu vuc cdng trinh Phii Gia - Tir Lien
3. KET LUAN
- Cdng trinh chinh tri bang cac giai phap dilu chinh ddng chay dugc sii dung d nude ta vdi sd lugng dang ke tir nhirng nam dau thap ky 70 cua thd ky 20, dac biet la tren cac sdng cua he thdng sdng Hdng. Loai cdng trinh nay dugc phat trien lidn tuc va rdng khap, thu dugc nhiing hieu qua dang khich le. Nhitng MH xay dung tir nhiing nam 1970, 1971 din nay van tdn tai, nhung MH dang va se dugc xay dung ngay cang nhieu, chiing td nhiing hi$u qua tich cue ma nd mang lai.
- Cac dang cdng trinh dilu chinh ddng chay ngay cang dugc phat trien da dang hon, qui md cua cac hang muc cdng trinh ngay cang lon. Sd lugng cac MH trdn mdt doan sat Id da tir 3 len tdi 19 nhu truong hgp Yen Ninh trdn bd Hiiu sdng Hdng, 15 tren doan Tam Xa - Ha Ngi. Chiiu dai ciia cac MH ban ddu khoang 20 -H 30m (thudng ggi la MH dku ga) nhu d Cd Dd, Phii Cudng Ha Tay, hien nay
da cd nhiing MH dai hon 100m, nhu MH sd 6 ciia cum cdng trinh Nghi Xuydn dai 140m.
Ket cau cua cac MH tir so khai la cac cum canh cay, loi dat boc da, hien nay phd bien la da hoc va cac khdi be tdng, dac biet cd loai MH cgc be tdng cdt thdp. Khoang each giiia cac MH thdi ky bat dau bd tri rat thua, gay ra su sat Id giua cac MH nay da dugc dieu chinh phu hgp hon.
Nhung nhiing van dd KH-CN ciia loai MH chua dugc giai quyet sau sic la:
- Cao trinh dinh MH: Trong chinh tri sdng, hieu qua cong trinh phu thudc nhieu den viec xac dinh diing ddi tugng chinh tri la miia nude nao dd tinh toan dinh cdng trinh can dat den. Viec xac dinh sai ddi tugng chinh tri lam cho hieu qua cdng trinh khdng dat dugc, tham chi cdn cd hieu qua ngugc lai. Vi du nhu cdng trinh chinh tri phyc vu giao thdng thiiy Phii Gia - Tii Lien, cao trinh dinh +5 ^ +6 thap hon muc nude chinh tri tir 3m din 4m, vi vay khi ddng chay tran qua dinh se gay nhirng didn bien cue bd ngoai y mudn.
- Gdc lech cua MH: chua dugc xac dinh theo kit cdu ddng chay mdt each bai ban ma bd tri gdn nhu khdng tuan theo mdt nguyen tac nao, trong mdt cum edng trinh cd cai xien thuan, cd cai vudng gdc, cd cai hoi cheeh ngugc. Mac dii gdc lech cua MH cd tac dung quylt dinh din hieu qua cua cdng trinh.
- Cdng trinh MH xay dung trSn cac doan sdng cong, doan sdng cd ddng chay ngap sau tren bai rdng cung chua dugc nghien eiiu bai ban vd kit cau ddng chay va bd tri khdng gian cdng trinh, dan din nhiing cdng trinh da xay dung khdng phat huy hieu qua.
- Cd mdt sd cum MH khdng dugc bd tri theo mdt tuyin chinh tri cd co sd khoa hgc, ma vach mgt each tiiy tien, vi vay chieu dai MH khdng thich hgp.
- Ndi bat Idn cae tdn tai la, cac he thdng
TAP CH[ KHOA HOC VA CONG N G H £ T H O Y L O I S 6 27 - 2015 79
I KHOA HOC ^ ^ . u u j i a n ^
MH dupe thiet ke ma khong co cac nghien va tu sir kip thai.
ciru ky tren mo hinh vat ly hoac mo hinh XTI,.~,«« .,1,- .- , . . , .. j - . • i, u- • , . , , . , , . » , . . . . Mhung phan tich, danh gia da trinh bay o toan, nen khong du bao duac hieu qua eua ,^g„ ^^^ ^.^ ^^^ ^^^ ^^^^^ ^..^ ^^. ^^
chiing. Sau khi dua vao xay dung, cong . ^ N , a day khong ki din cac khia canh trinh khdng dugc theo ddi duy tu, quan ly „« ^^\
TAI LIEU THAM KHAO
[1] LiroTig Phuong Hau (2010), Nghien cuu cdc gidi phdp khoa hgc - cdng nghe cho he thdng cdng trinh chinh tri sdng tren cdc doan trgng diem viing ddng bdng Bdc Bg vd Nam Bd. Detai khoa hgc - cdng nghe cap nha nude, ma sdKC.08.14/06-10.
[2] Luong Phuong Hau (2010), Chi ddn ky thuat cdng trinh chinh tri sdng; NXB Xay dung.
Ha Ngi.
[3] Lu- Ngoc Lam (2005), Ludn vdn thac sTky thuat - Dai hgc Xdy dung.
TAP CH( KHOA HOC VA C O N G N G H £ T H O Y LOI S 6 27 - 2015
