GT thiết kế công trình dẫn và tháo nước

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BQ NONG NGHI~P VA PHAT TRIEN NONG THON
TRUONG CAD DANG CONG NGH,f; - KINH

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THiry LQI MIEN TRUNG

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DIl an Khoa hqc cong ngh~ nong nghi~p - Giai dO\ln2010-2012
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Ti~u hqp phin 3.1

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H\lng myc: Bien SO~lDGiao trinh h~ Cao ding
Nganh Cong ngh~ Ky thu~t xay dl}'llg

GIAOTRINH
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THIET KECONG TRINH

nAN vA THAo Nuac
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Bien soan:
. LE NGOC NHUAN

-THfiVilN
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TRUONGCAO OANG c61~G NGH~
. KINHl~ vA !HUY HI'I Mj~N TRUNG

86:

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HQi An 11/2012



UJINOIBAu
Nganh Cong ngh~ ky th~t xay dl,lllg, h~ cao ddng la mQt nganh moo duQ'c thanh
I~p; vi v~y de dap Ung duQ'C.nhu cAu ve giang d~y va hQc ~p cua giao vien, sinh vien,
Tnremg Cao ddng cong ngh~ - kinh t6 va thuy IQ'imien trung dii t6 chtic vi6t bQ giao trinh
cho nganh nay.
Giao trinh "Thi6t k6 cong trinh ddn va thao nu6c" la tai li~u de giang ~y va hoc .
~p mon " Thi6t ke cong trinh ddn va thlio nu6c " cho h~ cao ddng chinh quy, nganh Co~g
ngh~ ky th~t xay dl,lllg, chuyen nganh thuy IQ'i. Sinh vien, hQc sinh mQt s6 nganh khac;
giao vien va can bQ ky thu~t co the tharn khao de hQC~p ho~c de tinh toan, thiet k6 trong
th\lc teo
Kh6i IUQ'flgkien thtic va k6t c~u cua giao trinh vi6t theo chuang trinh mon hQc "
Thi6t k6 cong trinh ddn va thao nu6c " do Tnremg Cao ddng cong ngh~ - kinh te va thuy
IQ'imien trung bien so~, voo 3 dan vi hQc trinh.
C~u trUe giao trinh gBm 3 chuang:
Chuqng I. Khlii quat chung ve cong trinh ddn va thao nu6c tren h~ th6ng kenh
Chuang 2.Thi6t ke kenh ddn
Chuang 3. Thi6t k6 cong trinh tren kenh
NQi dung giao trinh, trinh bay nhUng ki6n thtic Cva cac cong trinh tren kenh vila va nh6 (cAp III, IV) thuemg dimg 6 Vi~t Narn.
Trong qua trinh bien so~, toi dii vi6t theo phuang cham " C\l the, co ban, hi~n d~
va Vi~t narn" theo trinh dQ Clla sinh vien cao ddng hi~n ~. NhUng nQi dung Clla giao trinh
duQ'c c~p nh~t theo cac tieu chuAn hi~n hanh cua Vi~t Narn.

Noi chung ki6n thtic ve " Thi6t k6 cong trinh ddn va thao nu6c " la r~t rQng va lien
quan d6n r~t nhieu mon hQc, nhieu liinh V\lC; giao trinh nay chi cung cAp nhUng kien thtic
co ban, cAn thi6t nh~t; vi v~y trong qua trinh hQc t~p, sinh vien cAn thuemg xuyen on luy~n
va c~p nh~t nhUng ki6n thuc co lien quan 6 cac mon hQc khac, 6 liinh V\lCkhac; phili bi6t
tu duy cM dQng, sang ~o; dBng tho; phai thuemg xuyen lien h~ voo th\lc tien de co the
nfun vfrng Iy thuy6t va co the ap dl,mg duQ'CIy thuy6t vao th\lC tien mQt cach sang ~o nh~t.
Toi xin chan thanh cam an cac ThAy, Co Vii Hoang An, Hoang Thi HQ'i va cac
giao vien, can bQ trong trllemg Cao ddng cong ngh~ - kinh t6 va thuy IQ'imien trung dii
dong goP. nhieu y ki6n tronll qua trinh bien so~; cam an cac mc gia di tnr6c dii viet nhUng
tai li~u de toi tharn khao viet trong giao trinh nay.
Trong giao trinh, chfic rdng khong trlinh kh6i thi6u s6t, toi r~t mong nh~ duQ'c S\l
gop y chan thanh cua b~ dQc.

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ChlfO'Dg1 : KHAI QUAT CHUNG
1.1. KHAI QUAT vt CONG TRiNH DAN VA THAo Nl10C
1.1.1. Khai quat chung

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MQt h~ th6ng tucri gAm co 2 OOom clIng triOO: Nhom cac cong triOO dau moi va
OOom cac cong triOOtren keOO.Cae cong triOOtren keOOgAm co miill1gluCrikeOO( keOO
chiOOva cac keOOOOanh)va cac cong triOOtren keOO.
H~ th6ng keOOdUng dll dfuI nuac til ddu m6i d~n neri sir d\lllg (ruQng cdn tum, neri
>
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can cap nU(Jc...
.
,
Cong triOOtren keOOla OOfrngcong t?OO duQ'c lam tren cac tuyen keOO.C.hUngco
thll duQ'c dUng dll dfut nuac cho keOOkhi can vugt qua chuang ng(li v~t ho?c de bao v~
keOO, dll dieu ti~t dong chily trong keOO...
..
Ngoai ra trong h~ th6ng tuCricon co h~ th6ng tieu ( ding gAm miill1gluCrikeOOva
cac cong trinh tren keOO);Vi v~y trong mQt M th6ng thuy nong noi chung ( bao gAm ca
tucri va tieu) miill1gluCrikeOOva cong triOOtren keOO la rdt nhieu va rdt da diill1g;m6i lo(li
co mc d\lllg, cdu t(lO, dieu ki~n ap d\lllg ... khac nhau, cach tiOOtoan thi~t k~ cling khac
OOau.
Tai li~u nay chi trinh bay vcri cong trioo dfuI va thao nuac tren M th6ng keOOtucri.
Khi dii nfun duQ'CnQi dung cua vi~c thi~t k~ cong trioo dfut va thao nuac tren h~ th6ng
keOOtum ta co thll v~ d\lllg di\ thi~t k~ cho keOOva cac cong triOOtren h~ th6ng keOOtieu
ho?c h~ thang khac.
.
1.1.2. Kenh dAn
1. Kenh ha (kenh dan ha)
KeOOh6 la keOOrna ben tren di\ ha ( khong co dAp ddt), m?t thoang duQ'c ti~p XIlC
vm khi trm. nen dong chily trong keOOluon la dong khong ap.
DiilI1gm?t cAt ngang kenh ha thong d\lllg la diill1gm?t cAt hiOOthang va chi! OO~t,
ngoai ra con co cac diill1g:m?t cAthiOOparabol hiOOqua trirng ...
KeOO ha la diill1gkeOOdfut duQ'c irng d\lllg rQng rill OOdtso vm cac lo(li keOO dfut
khac (tren 90%).
Cae diill1gm?t cAtva cAu t(lOkeOOthuang dUng se duQ'ctriOObay a chuang 2.
2. Kenhngdm
KeOOngdm la keOOlam ngdm duCriddt, ben tren keOOco dAp ddt OOung dong chay
qua keOOvfut la dong chily khong ap.

DiilI1gm?t cAl ngang keOO thuang dUng la diill1gm?t cAl chi! OO~tho?c tron. Cac
diill1ghiOOvom, hiOOqua trirng .. .it duQ'c sir d\lllg trong th\lc t~.
S\l khae bi~t ccr ban gii!a keOOh6 va keOOngdm la a ben tren keOOkhong co dAp
ddt va co dAp ddt.
Do keOO ngdm ben tren co dAp ddt nen coi OOu khong co di~n tich chi~m ddt,
khong SQ'bi xoi la do mua ... Tuy OOiendiill1gkeOOnay quan Iy kho, kiOOphi xay d\lDg dAI,
vi v~y no chi duQ'c sir d\lng trong tmang hgp ca bi~t, vi d\l: keOOdi qua vling do thi, vling
suan dAi ...
3. M(jt

s6 d{lng

khitc

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- Kenh dfu1 d(lIlg mang n6i: Kenh d(lIlg nay g6m m(lt M thBng gia dO' ( thuOng
bdng be tong cBt thep, tre, g6 ... ) d~ dO'mang dfu1nuo-c a ben tren ( bdng be tong cBt thep,
xi mang lum thep, ton, g6 ... ).
D(lIlg nay chi nen dUng trong cae truOng h?p' sau: Tuy~n kenh di qua vimg dAt
thb nuac m(lIlh, lAy th\lt; tuy~n kenh di qua vimg doi nw ho(ic thung liing co hien tugng
Sf,itla, kern 6n djnh ...ho(ic khi cAn ti~t kiem dien tich chi~m dAt d~ danh dAt canh tac.
- DuOng Bng dfut: D(lIlg miy tuang t\r ( d6ng d(lIlg ) nhu kenh ngb, nhung dong
chay qua dUOng Bng thuOng thi~t k~ Ill.dong chay co ap, nen ti~t dien Bng thuOng nh6 han.
Tuy nhien do Ill.dong co ap va ap h,rc nuac thuOng cao ho{ic rAt cao nen viec chBng ro ri
nuac qua cac kh&p nBi Bng Ill.vAn de rAt quan trQng so vm cac d(lIlg dfut nuac ho.
DuOng Bng dfut chi thuOng dUng vm cac cong trinh co c(lt nuac cao ( trf,iffi thuy
dien, he thBng cAp nuac sinh hOf,it,cong nghiep ... ), v(it lieu thUOng dUng Ill.Bng thep, Bng
nh\fa duc sfu1.

- DuOng hAm: DuOng hAm ciing Ill.mQt d(lIlg kenh ngAm, nhung dugc thi cong
bdng cach dao qua d6i, nuL D(lIlg nay thuOng co ti~t dien Ian, thi cong phtrc tf,ip... nen no
chi thuOng dUng cho cong trinh Ian, quan trQng ( trf,I.mthuy dien) khi kenh cAn vugt qua
d6i, nw.
1.1.3. Cong trinh tren kenh
Sa d6 bB tri m(lt sB 10f,iicong trinh tren kenh tum mo ta a hinh 1-1.

1

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Su6i

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Duong

Hinh 1-1. Set d6 m(li s6 c6ng trlnh tren kenh lUcri
I.C6ng illYm~ac: 2. C6ng di/!u ti€t; 3. au mling; 4. C6ng 1u6n
5. C6ng qua duong; 6. B~c nuoc (D6c nuac); 7. C6ng tieu;
8. Tran vao; 9. Tran ra; 10. O,u 6 t6; 11. O,u tM so

1. C6ng trinh ldy nuuc
Cong trinh lAy nuac ( cBng dAu kenh): DUng d~ lAy nuoc tir kenh dp tren ho{ic tir
ngu6n vao kenh. Khi cBng lAy nuac Ill.cBng lAy vilo kenh dp dum con gQi Iii cBng chia
nuoc, cBng phan nuac. Df,ing thuOng dUng Iii cBng h6 vii cBng ngAm, co cua van de dieu
tiel.

2. C6ng trinh di~u tiit nuuc

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Cfmg triOOdi8u ti~t nuac mn keOO( tum ) dUng d8 di8u ti~ m\lC nuac trong keOO.
Dl;Ulgthuemg dUng la dang nu6c len d8 dam Mo m\lc !!uac ,cho cac c6ng dAU;keOO cAp
dum lAy duqc dli nu6c theo yeu cAu. Ngoai ra c6ng dieu tiet con dUng d8 dieu ti8t luu
luqng cho keOOkhi tum luan phien .. "
.
.
C6ng di8u ti8t thuemg duqc b6 tri 6 dol;UlkeOOdai, co ton thiit cQt nuac 16n, khong
dl).tdugc m\lC nuac kh6ng ch~.,
.
,
Dl;Ulgcong triOOthuemg dUng la cong ha, co cua van dieu tiet.
Tl).iOOiing nm co S\l thay d6i dQt ngQt v8 dQ cao m\lc nuac (truac b~c nuac, d6c
nuac) cfuig cAn b6 tri c6ng di8u ti~t, tuy nhien de tranh lang phi, ngum ta chi cAn b6 tri
cua van ho~ cua phai 6 Clravao Cllab~c hay d6c nuac de di8u ti8t.
3. Cong trinh vu(1t chuang ng(li
Khi keOO dful g~p cac chuang ngl).iv~t tren duemg dful OOusong su6i, duemg giao
thong, de, keOOkhac (keOOtieu) ... ta phai lam cong triOOde dful nuac trong keOOvuqt qua
cac chuang ngl).i v~t nay. Cong triOOdl;Ulgnay gQi la cong trioo vuqt chuang ngl).i (cong
trinh vuqt chuang ngl).iv~t, cong trioo vuqt v~t can ).
Cong triOO vuqt chuang ngl).i thuemg dUng la c6ng ngk, c6ng lu6n (xi phOng
ngugc), cAu mango
4. Cong trinh n6i tlip
Khi dQc keOO dful (keOO ha ho~c keOO ngk) g~p dja hiOO qua d6c ta pMi lam
cong triOO de chuyen nuac til tren cao xu6ng thAp, de dam Mo dong chay trong keOO

khong pha,hol).i keOO?O~Cde phia hl).luu keOOkhon~ phai dAp cao. ~~u k~OO~p qua cao
se lam khoi luqng dap Ian, kinh phi xiiy dl,lng OOieu, di~n tich chiem diit nhieu ... Dl;Ulg
cong triOOnay gQi la cong triOOn6i ti8p.
Cong trioo n6i ti8p g6m b~c nuac (mQt cAp ho~c nhi8u cAp) va d6c nuac. Cong
triOOtren keOOthuemg chi dUng b~c nuac 1 cAp.
5. Cong trinh thao nutlc (c6ng tieu, trim bang ...)
Cong triOOthao nuac ( tren keOOtum) la cong trioo dUng de thao nuac thua trong
keOOho~c do nuac mua chay ngang qua keOOOOfunbao v~ keOOkhong bj Sl).tla, va keOO.
Cong triOOthao nuac tren keOOtum g6m:
- C6ng tieu: Ihao nuac mua til ben nay chay ngang qua ben kia keOOkhi cho nuac
chay dum day keOO.C6ng tieu thuemg lam dl;Ulgc6ng ngk, c6ng lu6n.
.
- Iran bang : Ihao nuac mua til ben nay cMy ngang qua ben kia keOO khi cho
nuac cMy tren m\l"c nuac Clla keOO.Iran bang thuemg su d\lllg khi cAn tieu qua keOO vm
luu luqng tieu khong Ian va cao dQ m~t dAt tl,lnhien cao.
- Iran ra : Thao nuac qua ba keOO, til trong keOOra ngoai keOO.
Iran ra co nhi~m V\I thao nuac thua trong keOOra ngoai. Nuac thua co the do nuac
mua ho~c do mQt Iy do nao do nuac trong keOObj thua ra: do nuac mua 2 ben tran vao, do
c6ng dAu keOO rna qua Ian, do cac cong lAy nuac tren keOOkhac dong ...
- C6ng thao nuac cu6i keOO
Khi keOO la keOOM, n~u luu luqng keOOtuang d6i Ian ( Ian han hay bdng 0,50
3
m /s ) thi 0 cu6i keOOpMi b6 tri c6ng thao nuac de thao bat nuac khi m\lC nuac trong
keOOdang qua cao ho~c de thao Cl;UlkeOOph\lc V\l cho vi~c nl).ovet, sua chua keOO, cong
triOOtren keOO.
6. Cac cong trinh khtic
a. cau qua kenh

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. cAu qua kenh de ph\lc V\l giao thong qua kenh. cAu qua kenh dugc phan thanh 2
lo(li: cau 0 to va cAutho sa. cAu 0 to sir d\lOgkhi kenh c~t qua duemg co 0 to qua l(li, cAu
tho sa bUnkhi kenh c~t qua duemg nh6 kh6ng co 0 to qua I~i ho~c khi kenh khong c~t qua
duemg nRo. Khi khong co duemg giao thong c~t ngang kenh nhung i:1 nhUng vimg co san
xuAtnong nghi~p, i:1 nhUngnm co dan cu qua l(li thl trong khoang 100m dSn 200m cAnb6
tri mQtcAutho sa de thl$t ti~n trong di l(li, san xuAtCllangum dan.

b M6(

s6 c6ng

trinh khac

N~oai nhUng cong trinh !ren, tren h~ th6ng kenh, tily vao muc dQ1611nh6 Cllakenh
con co the co cac d~g cong trinh sau:
- Con/iltrinh do nuuc: chi b6 tri i:1 cac kenh 1611.
- Be lang cat: De I~g bUn cat, tru&ckhi nuuc chily vao cong trinh d~ bi bAi I~g (
c6ng lu6n, cAumang) ho~c chily vao do~ kenh ngdrn hay duemg 6ng ...
- BSn rna: De dan lam nai rna tay chan, d\lOgC\llao dQng... khi cAnthiSt.
1.2. KHAI QUAT vE THItT KE CONG TRINH DAN VA THAO Nuac
1.2.1. D,c diim chung vi thiit ki cong trinh dAn va thllo nric
Con/il trinh ddn va thao nuuc tren kenh tum noi chung dSu.Ia cong trinh ~6,
thuemg Ja cap IV (trir kenh va cong trinh thuQc kenh chinh Cllah~ thOng 1611).D~c diem
chung Clla cong trinh ddn va thao nuuc la chUng phan b6 tren mQt m~t bfutg rQng, diSu
ki~n dia hinh, dja chAt,tMy van ... da d~g; chUnglo~i cong trinh co the sir d\lOgcho mQt
m\lC dich sir d\lOgcling rAt da d~g; cac nQi dung, yeu CAuvS tinh toan thiSt kS cho cac
cong trinh ding cit da d~g ... Vi v~y khi thiSt kS cAnhieu ro d~ diem va diSu ki~n trng
d\lOg Clla tUng lo~i de co thS h,rachQn dugc lo~i cong trinh hgp Iy; cAn hiSu ro cac nQi
dung, yeu cAu vS tinh toan thiSt kS cho tirng lo~i cong trinh dS co thS tinh toan thiSt kS

cong trinh dugc chQndam bao cac yeu cAuvS thiSt kL .
1.2.2. Nguyen t~c thiit ki cong trinh dAn va thllo DIrac
ThiSt kS cong trinh ddn va tMo nuuc hay bAtcu mQt cong trinh nao, phili tuan thll
cac nguyen Mc sau:
- Cong trlnh pMi dap trng dUng cac nhi~m Vl,IcM ySu Cllacong trinh da dugc d(it
ra, d6ng thm pMi v~ d\lOgnguyen t~c " 19id\lOgt6ng hgp" trong thiSt kS dS phat huy hSt
hi~u qua Cllacong trinh.
- Phai dam bao cong trlnh va bQph~ cong trinh lam vi~c an tooo trong mQitruemg
hgp, d6ng thm kinh phi xay d\Ing phai nh6 va phil hgp vm diSu ki~n tt,rnhien, xa hQi Clla
cong trinh; diSu ki~n thi cong, quan Iy, sira chua thu~ 19i;dam bao tinh my quan Cllakhu
Yt,rc;khong lam t6n h~i dSn moi trnemg khu vt,rcxay d\Ing, vimg Ian c~ va d(ic bi~t la
vimgh~luu.
- Cong trinh phili co tinh hi~n d~i, ap d\lOgcong ngh~ thiSt kS, thi cong va quoo Iy
tien tiSn, pM hgp vm quy mo, diSu ki~n xay d\Ing t~i ch6 va xu thS pMt triSn Clla dia
phuong, khu Yt,rCva CllaQu6c gia.
- Phai hiSu ro cAu~o, d(ic diSm xay d\Ing cila cong trinh va tirng bQ ph~ cong
trinh; hiSu ro diSu ki~n tt,rnhien, xa hQi Cllakhu Yt,rCxay d\Ing dS co thS It,rachQn dugc
lo(li cong trinh, cdu t~o cong trinh hgp Iy.
- N~ ch~c cac yeu cAuvS tinh toan, It,rachQnva cac phuong pMp, d(ic diSm Clla
tUng phuong pMp tinh toan dS co thS v~ d\lng vao tinh toan, It,rachQn cac thOng s6 clla

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cong trinh; tinh toan ki~m tra S\l lam vi~c an toan cua cong trinh va timg bQph~ cong
trinh... mQtcach hgp Iy.
.
_ Tuan thu dUngcac tieu chufut,quy p~ hi~n hanh,Cllanha nucrc..
,
Rieng v~ thi~t k~ cong trinh dfutva thao nucrc, con can cM y cac d(icdiem, yeu diu

rieng Cllatimg 10\1icong trinh, cac bQph~ cua chUngd~ c6 the l\la chQnduqc cAu1\10;nQi
dung, phuang philp tinh toan thi~t k~ hgp Iy nhAt.vAn d~ nay se duqc trinh bay trong timg
chuang vm timg lo\li cong trinh rieng.
1.2.3. Xae djnh eip eua dlng trinh va cae chi tieu thiit ki
1. Xac dtnh cap cua c6ng trinh

cAp Cllacong trinh cM y~u duqc xac dinh theo QCVN 04-05-2012, tra bang PL
1-1-1, ph\ll\lc 1-1. Khi xac djnh dn chi!y nhUngnQidung sau:
- cAp Cllakenh va cong trinh tren kenh n6i chung, cM y~u ph\l thuQc vao nang l\lc
ph\lc V\I (nhi~m V\I) cua kenh ho(iccua h~ th6ng cong trinh, nen chi trli cac m\lc 1,2, 3 Clla
bang PL I-I-I, ph\ll\lc I la duo
- Rieng vm tuang chiin dAt,cApCllan6 con ph\l thuQcvao chi~u cao va n~n tuang
; Nen sau khi phan c~p theocac m\lc 1,2,3 cua bang PL 1-1-1 ta cAnxac dinh c~p theo
m\lC 6 cua bang PL 1-1-1 (tuang chiin), sau d6 ta chQn cApIan han d~ lam cApthi~t k~
. chotuang.
- Ngoai ra cAncM y riing: cApCllacong trinh c6 th~ duqc nang len ho(ic h\1xu6ng
I c~p illy vao nhUng d(ic di~m rieng bi~t cua cong trinh, duqc neu a cac ghi chu trong ph\!
I\lc 1-1-1
- N~u cong trinh la cong trinh thu y~u ho(ic cong trinh t\lffithm, c~p Cllacong trinh
ph\l thuQc vao cApcua cong trinh chu y~u trong cimg h~ th6ng dful, xac dinh theo bang
PL 1-1-2, ph\ll\!c I-I.
2. Xac dtnh cac chi tieu thilt

ki

Sau khi xac dinh duqc c~p Cllakenh va cong trinh, din cu nhi~m V\I va d(ic di~m
cua cong trinh ta phai xac dinh cac chi tieu thi~t k~ chinh cua cong trinh d~ lam co so cho
vi~c thi~t k~.
Cac chi tieu thi~t k~ chinh g6m:
- Muc bao dam thi~t k~ cua cong trinh thuy 19i(ph\ll\!c 1- 2)

- TAnsu~t luu luqng, m\lCnucrcIan nh~t, nho nh~t thi~t k~ va ki~m tra cong trinh
(ph\!I\lC 1-3)
- TAnsu~t m\lCnucrc Ian nhAtd~ thi~t k~ cac cong trinh t\lffithm ph\lc V\I cong tac
dfuldong, ch(in dong ( ph\!l\lc 1-4)
- H~ s6 an toan cho phep [K) cua cac cong trinh va cac bQph~ cua chUng ( ph\!
I\lc 1-5)
D~ xac dinh 10\1ichi tieu, cac trj s6 d~c trung cho m6i chi tieu cho mQt lo\li cong
trinh nao d6, ta can cu vao nhi~m V\I va d~c di~m lam vi~c cua cong trinh do.

8


CA.UHOI ON T~

CHUONG 1

I. Hay trinh bay cac d\Ulg kenh dful; neu d(ic diem va di&u ki~n sir dl).llg Clla m6i
lo(U.
2. Hay ke ten cac lo(U cong trinh tren kenh, nhi~m V\I va vi tri ~g dl).llg Clla m6i
lo(Ucong trinh ..
3. Neu dinh huang cach xac djnh d.p cong trinh.
.
4. Ke ten va neu y nghia cua cae chi tieu thi~t k~ chinh dUng trong thi~t k~ cong
trinh thuy 19i.

9


CbU'O'Dg 2. THutT ICEKENH nAN
2.1.TM LI~U TmET ICE KENH

.
D~ thich k€ kenh tum, dBi vm nhftng kenh Ian ta can cac tai lieu sau:
1. Tai lieu dia hinh
,
.
- Ban d6 UTM Clla khu V\l'C, thuimg dimg ban do ty Ie 1150.000 ho~c 1125.000
- Binh d6 khu tum, thuimg dung ban d6 tY Ie 1110.000; 115.000
- Ban d6 giai thira d6ng ruQng Clla khu tum, n€u co.
- cAt dQc, cAt ngang dia hinh tuy€n kenh. cAt dQc thuim& dimg tY ~e 11100
112000; cAt ngang thuimg dimg ty Ie 11200;11100; 1150; 1125; chieu rQng moi m~t cat
ngang kenh til 10 + 50m my thuQC vilo kich thuCrc m~t cAt ngang (d\f ki€n) cua kenh. Vi
tri dn do ve m~t cAt ngang Iii cac vi tri co dia hinh dQc tuy~n thay dBi dQt ngQt, vi tri d\f
ki~n lilm cong trinh tren kenh, vi tri kenh dBi huang tuy~n. Khi dia hinh dQc tuy~n bkg
phkg hay tuang dBi bkg phkg vii khong co vi tri ca biet nilo thi khoilng 100m do mQt
m~t cAt ngang.
- Sinh d6 dQc tuy~n kenh ( con gQi Iii binh d6 IQtuy~n). Ph(lIl1vi do ( theo phuang
ngan~ kenh) my thuQC vilo kich thuCrc m~t cAt ngang d\f ki~n Clla kenh. Lolli nily thuimg
chi can cho kenh quy mo Ian, dia hinh phuc ~p.
2. Tai lieu khi tUQ11g,thuy van
- Dieu kien khi tuQ11gkhu V\fC:Mua, gio, dQ fun, nhiet dQ...
- Dieu kien thuy van: Dong chily, m\fC nuCrcbi~n, song suBi... trong khu V\fC.
3. Tili lieu dia chilt, thB nhuang vii cac tai li~u khac
- Dieu kien dia ch~t dQc tuy~n kenh, cac bai v~t li~u (d~t) n~u co.
- Dieu ki~n ve thB nhuang, ciiy tr6ng, thai V\lgieo tr6ng ... Clla khu tum
- Dieu kien giao thong
- Dieu ki~n ve di~n, nuCrc(d~ thi cong), v~t li~u xiiy d\fllg, dieu ki~n thi cong ...
Vm cac kenh co quy mo nho ho~c khong Ian lfun ta can lugc be) mQt sB tai lieu (
daneu tren) d~ giilm kinh phi ciing nhu thai gian khilo sat.

9;

.2.2. LlfA CHQN TUYEN KENH vA 86 TRI CONG TRiNH THEN KENH
2.2.1. Khlii quat vi m\lng hrm kenh tum
H~ thBng kenh tum bao g6m m\lllg lum kenh tum vii cac cong trinh tren kenh.
M\lIlg lum kenh tum g6m: kenh chinh, cac kenh nhlinh c~p I, II, III... Kenh cAp cuBi cimg
Iii kenh cAp nuCrcvilo kholinh tum gQi Iii kenh chan r~t ( Hinh 2-1).
Ten Clla cac kenh dugc d~t nhu sau:
- Kenh chinh: KC
- Kenh nhlinh c~p I: N I, N2, N3 ...
- Kenh nhlinh c~p II: NI-I, NI-2, NI-3...
N2-1, N2-2, N2-3 .
N3-1, N3-2, N3-3 .
- Kenh nhlinh cAp III: NI-I-I, NI-I-2, NI-I-3 ...
Khi h~ thBng co nhieu kenh chinh thi co th~ d~t ten Iii KCI, KC2 ... ho~c co th~
dimg ky hi~u khac d~ d~t cho tUng kenh ( N, S, B ... ). Kenh chan r~t khong d~t ten.

10


5

Hinh

2-1.

SCI

d6 IDling 1um kl!nh

tum

2.2.2. LI}'ll chqn tuy~nkenh
1. Jrhaiquatchung
L\Ia chQn duQ'c tuy&n keOOde thi&t k& la cong vi~c quan trQng ddu tien trong thi&t
k&mQt con keOO. De chQn duQ'c tuy&n xay d\IOg cho timg keOO clla mQt h~ th6ng ta phai
k&thgp giii'a biOOd6 khu tum vm th\Ic dia; cong vi~c thm'mg duQ'c ti&n haOOOOusau:
- Truac h&t din cll vao biOOd6 khu tum, ta ti&nhaOOve sa d6 ml;lllg lum keOO( ve
tren biOOd6 khu tum). Buac OIlY gQi la thilt ki m(it bimg h? thr5ng kenh
- Ciin Cll vao sa d6 ml;lllg lum keOO dii ve, ta di th\Ic dja de xac djOO tuy&n C\l the
cho timg keOO.
Hal buac nay thuang phai ti&n hanh song son~. Khi di th\Ic dja thAy ve chua hgp
If thi ve I~ sa d6. NguQ'c liilikhi ve I~ sa d6 thAy tuyen chQn tren rhwcj dia cdn pMi dieu
chiOOthi dieu chiOO liili.Thm'mg, vm cac keOO Ian pMi lam nhieu Idn mm xong; keOO 006
co the lam 1 d&n2 Idn la xong.
Sau khi chQn duQ'c tuy&n cho ti&n hanh phong tuy&n, dong CQCva khao sat dja
hiOO,dja chAt.
2. Br5tri tr5ngthi m(Jng h,6'i kenh tu6'i
Khi b6 trl t6ng the ml;lllg lum keOOcdn tuiin thll tlhUng nguyen cic sau:
- Phai xet tm quy hOiilchtr6ng trQt trong khu V\ICva nen b6 tri keOOrieng bi~t cho
timg vling tr6ng trQt, OOu vling tr6ng Ilia (nuac), vling tr6ng mau, vling tr6ng cay cong
nghi~p ...
- H~ th6ng keOO tum phai duQ'Cb6 tri d6ng ththanh mQt h~ th6ng tum, tieu hoan chiOO.
- Cdn b6 tri keOO OOanh sao cho ph(lffi vi tum clla chUng nk gQn trong dja gim
khu V\IChaOO chlOO ho?c cac dan vj san xuAt OOu nong tTuang, hgp tac xii ... de vi~c t6
chUc san xuAt va quan If phan ph6i nuac duQ'c thu~ ti~n, hgp If.
3. Ch(in tuyin cho timg kenh
Khi chQn tuy&n keOOtuai cdn tuan thll cac nguyen t~c sau:

11

• TuySn kSnh nSn di trSn vimg cao dQ tuang d6i cao Clla khu V\fCde vi~c tum tg
<
.
chay dugc phat huy cao nhat.
.'
,
_ TuYSn kSnh tum nSn.di qua vimg dAt bn dinh ( khong hi 100 S\lt, s~t 10.. ')'. it thfun
de kSnh cO the him vi~c bn dinh va giam kinh phi xay d\Il1g. .
.
• TuySn kSnh cAp trSn pMi t~o dieu ki~n tht$lIQi dS xay d\Il1g cac kSnh cap dum
va cae cong trinh tren kSnh.
.
.
_ TuySn kSnh tum phai di sao cho kSnh it g~p chu60g ng~ v~t nhat, nhat la cac
chu60g ng~ v~t phai xu Iy phuc t~p nhu song.•su6i, khu diin.cu dong .duc.
,
- TuySn kSnh tum phai di sao cho khoi lugng dao dAp it, chiSm di~ntich dilt canh
tac it.
- TuySn kSnh tum nSn di sao cho vi~c thi cong, quan Iy dUQ"cd8 dang .
• TuySn kSnh tum nSn di sao cho kSnh co the kSt hgp ph\lc Y\l cho cac m\lC dich
khac: kSt hgp lam dUOng giao thong, dUOng day di~n ...

3. Chpn btin kinh cong cua kinh

o nhilng

.

do~ kSnh chuyen hu6og, tuySn
kSnh cful dUQ"cchuyen hUOng tir tir de tranh tbn
thAt CQt nucrc C\lChQ va tranh de dong cMy gay
xoi 10 ho~c h6i lfulg cho kSnh ( xem hinh 2-2 ).
Ban kinh cong r Clla do~n kSnh nSn chQn r = 5B.
Khi cful giam nh6 r thi phai co It$l chirng C\l the
va cful th6a milo dieu ki~n sau:

r2: 2B

(2.1)

s

Hinh 2-2. Rin kinh cong Clla kenh

tum

B: Chi~u rQng Clla m~t thoang ngang kSnh
irng vm lUll lugng thiSt kS

2.2.3. 86 trf cong trinh tren kenh
B6 tri cong trinh trSn kSnh thuOng dUQ"ctiSn hanh song song vm vi~c h6 tri m~g
lucri kSnh va chQn tuySn kSnh.
De co the chQn va h6 tri cac cong trinh trSn kSnh hgp Iy cful nghiSn CUu ky di~u
ki~n dia hinh, dia chAt vimg tuySn kSnh di qua; di~u ki~n khi tugng thllY van, xa hQi Clla
khu V\fC... d6ng thffi phai hieu ro mc d\lOg, d~c diem lam vi~c Clla tling lo~ cong trinh trSn
kSnh.
KSt qua clla vi~c chQn va h6 tri cong trinh trSn kSnh phai dUQ"Cthe hi~n trSn m~t
hAng h6 tri m~g hIm kSnh.

2.~.

tic

DJNH LUU LUQNG, DQ DOC

vA m10NG

MVCNUaC

TRONG

KENH

2.3.1. Xlic djnh hru hrqng thiet ke kenh
1. Cac logi luu IU(Tngthiit td kenh
D~ xac dinh m~t c~t kSnh tum cful dUng 3 cAp lUll Iugng
- LUll lugng thiSt kS Q ( Qtk) ( gQi t~t la lUll lugng kSnh) .
• LUll lugng nh6 nhAt Qmin.
- LUll lugng 160 nhAt Qmax (lUll lugng hAt thuOng).
LUll lugng thiSt kS Q la lUll lugng 160 nhAt trong hieu d6 lUll lugng thiSt kS thuQc
mQt do~ kSnh, mQt dp kSnh hay mQt h~ th6ng kSnh. BiSu d6 lUll lugng dUQ"cxay d\Il1g

12


sa

tren co

cua bi~u dB h~ s6 tum cUacac lo~ cay trBng do keOO do dam nhi~m tUm sau
khi d1iduQ'c di6u chiOO.
.
Khi xae diOO lUll lugng thiet ke keOO cAn phan bi~t lUll lugng th\lC cAn Qtc ( lUll
lugng th\lc te) va lUll lugng toan bi) Qtb.
LUll lugng thiet ke th\lc cAn Qtc la lUll lugng thiet ke cUa keOOchua k~ t6n thAt.
LUll lugng toan bi) Qtb la lUll lugng cAn chuY6n vao ddu keOOho~c ddu do(Ul keOO
d~ dam bao Qtc d1ixae diOO.
LUll lugng thiet ke Q dUng d~ xac diOOkich thuac m~t c~t keOOva d6 thiet ke cac
cong trinh tren keOO.
LUll lugng Ian ooAt QrnaxdUng d~ ki~m tra kha nling xoi la trong keOOva xac diOO
di) cao an toan cho diOOba keOO.
LUll lugng 000 ooAt QrnindUng d6 ki6m tra kha nling bBi I~g trong keOO, kha nling
dam bao tum tl,l chay d~ til do nghien Clm, thiet ke c2. Xac a;nh cae lO(li lltU lU(1ng ad thilt ki kenh
a. Xac a;nh lltU lU(1ngnho nhiit Qmin va lltU lU(1ng lUn nhiit Qmax
- LUll lugng 000 ooAt QrninduQ'c xac djnh theo bi~u dB h~ s6 tum thiet ke ho~c xac
diOO theo lUll lugng thiet ke keOOOOusau:
+ Khi xac diOOQrnintheo bi~u dB h~ s6 tum thi Qrnincua mi)t do(Ul kenh, mQt cAp
keOO,mi)t M th6ng keOOkhong duQ'c 000 han 40% lUll lugng thiet ke tuang wg.
Vi~c xay d\lllg bi~u dB h~ s6 tum cho mQt h~ th6ng la rAt phuc t\1Pva t6n rAt nhi6u
thai gian, cong suc, vi v~y no chi thucrng duQ'c xay d\lllg vm h~ th6ng tum Ian. Cac h~
th6ng tum 000 thucrng mugn cUa cac h~ th6ng tuang tl,l.
+ Khi khong co bi6u dB h~ s6 tum, co th~ chQn Qrnin= (0,40 + 0,60 )Q
- LUll lugng Ian ooAt QrnaxduQ'c xac diOOtheo lUll lugng thiet ke keOOOOusau:
Qrnax= K.Q
(2-2)
3
+ Khi Q < 1,0 m /s lAy K = 1,30
+ Khi Q = 1,0 +10,0 m3/s lAy K = 1,15 +1,20

+ Khi Q> 10,0 m3/s lAy K = 1,10 +1,15
b. Xac a;nh lltU lU(1ng thi€t ki
- LUll lugng thiet ke th\lc cAn Qtc xac diOOtheo cong thuc sau:
Qtc = q. W = LW,qi
(2-3)
q : H~ s6 tum thiet ke t\1im~t rui)ng ( IIs.ha)
q duQ'c xac diOOtheo bi6u dB h~ s6 tum cua cae lo~ cay trBng do keOO dam OOi~in
tum sau khi d1i duQ'c di6u chiOO. Vi~c xay d\lllg bi~u dB h~ s6 tum cho mi)t khu tum la
tuang d6i phuc t\1p va t6n OOi6u thai gian, cong suc; nen vm h~ th6ng tum 000, trj s6 q
thucrng duQ'c xae diOOtheo khu tum tugng tl,l.
Khi keOOph\! trach OOi6u10\11cay trBng khac OOau, q duQ'c tiOOtheo cong thuc sau:
q

=!
Lwiq,
W

(2-4)

T6ng di~n tich tuai do keOOhay do(UlkeOOph\! trach
Wi : Di~n tich cay trBng thu i do keOOhay do(UlkeOOph1,1trach
qi: H~ s6 tum cua trBng thu i
- LUll lugng toan bQ Q xac diOOtheo cong thuc sau:
Q = Qtc + Qt
(2-5)
W :

13

Ho~c:

Q = Q"

(2-6)

TJ
Q: Luu lugng thiet k~ t~ dAu kenh hay d~u do\U1kenh thi~t k~.
•
Qt: Luu I,!gn¥ bi t6n tMt ( chi! y~u Ili do thfun ), tinh til h(lluu d~n d~u kenh hay
dau dO(lnkenh thiet ke.
.
TJ : He sf, 19i dung cm kenh ( cua mQt kenh nao do). .
Trinh' tv tinh t~8n xae djnh Q la til kenh chan r~t trO' len va til cu6i kenh d~n dAu
kenh.
- Xac dinh Qt:
Khi chua co m~t c~t keOOxac djnh, t6n tMt nuoc do thk co th~ xac dinh theo
cong thirc sau:
Qt4v = 1O.AI.QI-ml
(2-7)
Ho~c:

tJ.
%
Qm'

0= --

(2-8)

o : T6n that nuoc thfun, tiOObfulg % cua Q
Qtdv = Luu lugng thfun tren I km chi~u diUkenh ( Luu lugng thfun d(Yllvi)
Q : Luu lugng nuoc trong kenh
tJ., mO, AI, ml: H~ s6 ph\! thuQc lo~ dat lam kenh xac diOOtheo ph\!l\!c (2-2) va
ph\!l\!c (2-3)
NgOlii ra n~u kenh lam vi~c dinh kY, thm gian mO'nuoc ng~, ho~c kenh co tkg
nuoc ng~
nong, kho thoat nuoc ck pMi xet them cac h~ s6 hi~u chiOO khac ( xertl
TCVN 4118 - 85).
- Xac dinh TJ :
f)~xac diOOh~ s6 19i dvng cua keOOck pMi xac dinh dugc luu lugng th\Cc ck,
luu lugng t6n that va luulugng toan bQ, sau do tinh TJ theo cong thlrc (2-6).
+ Khi thi~u tai li~u va vo; kenh nh6 ( co di~n tich tuo; khong qua 300ha, luu lugng
tuoi khong qua 0,30 m3/s) co th~ xac dinh TJ theo ph\!l\!c 2-4, sau do tiOOQ ( rna khong
ck xac dinh Qt)
Khi tinh luu lugng thi~t k~ cua kenh, n~u h~ th6ng co OOi~ukenh nen I~p bang d~
tinh d~ d~ qua sat.
Voi mQt mQt h~ th6ng keOOkhong lan, ta co th~ I~p bang tinh nhu bang 2-1
v 0; h~ th6ng Ian ta nen I~p bang tinh OOubang 2-1 OOung la cho tUng kenh nhanh
cap I ho~c dp II, sau do I~p them mQt bang khac d@tinh cho kenh chinh.
Ghi chu bling fink:
C(jt 8: Vtli kenh tinh Q theo 77: la luu IU(J7Igth!lc ti cua kenh; Qtt = qlua *OJlua +

a

qmau * lOmtiu
Vtli kenh tinh Q theo t6n thdt df)c kenh: la luu IU(J7Igchua ki t6n thdt df)c kenh
(Qat bling t6ng luu IU(J7Igcua cac kenh nhanh cua kenh dang tinh toan)
C(jt 9: .77.~Hf s6 Ir;i d',mg cua kenh, tra phl,lll,lc 2-4-1 va phl,lll,lC 2-4-2 va chf)n tr;
s6 nh6 di thitt ki

C(jt 10. 11: AI va ml: Cac hf s6 di tinh t6n thdtthdm df)c kenh Qt. tra phl,lll,lc 22; (chi cc1ntra va tinh khi kenh khOng cho phep tinh Q theo hf s61r;i dl,lng 77)
C(jt 12: Qtdv = 10. AlQI.ml

14


C(Jt 13: Q,= Qtilv.L (L IiI chi€u dili kenh - km)
C(Jt 14: Qtk = Qtll'/ ven kenh cha phep tinh Qtk tn,rc tiip thea 1'/ ha(ic Qtk=Qtt+ Qt
ven kenh /chong cha phep tinh Q thea hf s61(7i dlmg 1'/)
- Co th~ I~p bang tiOOQ theo t6n thAt tioo theo eong thue (2-8)
Blml!;2-1. Blml!;tinh hm Im;ml>dau kenh ehinh N eua mQth~ th6nl>khon" 160 (mdu)
hs tum
Qtt
Al
ml
Di~n tieh tum (ha)
L
Q'dv
(Qot) TI
(I/s.ha)
KeOO
(kID)
I/s.kID
lis
co
qUia qmau
COltia Olmau
12
9
10

11
4
5
6
7
8
1
2
3

N
NI
N1•I
N 1-1.1
NI•I_2
NI.2
..........
N2
N2.1
N2'1'1
N2.j.2
N2.2
..........
N3

Q,

Qtk

lis

13

lis

14

.

.

.

va

3. Xac d;nh hf s6 1(7id1,tngcua hf th6ng I'/h
!dim tra
H~ s6 19i d\lllg ella h~ th6ng keOOTIh xae diOOtheo eong thue sau:
TIh=

W

~ =

L qicoiti
Q.T

(2-9)

W,: Lm;mg nuae lAy vao m~t ruQng.
W: Lm;mg nuae lAy vao eong triOOdAu m6i.

qi: h~ s6 tum ella khu tum thu i.
COi:Di~n tieh tum ella khu tum thu i.
ti: Thai gian lAy nuae vao khu tum thu i.
T: Thai gian lAy nuae vao eong trinh d~u m6i.
Q: lUll Im;mg thi~t k~ (toan bQ) ella h~ th6ng.
i tiOOtir 1 d~n h~t s6 khu tum ella h~ th6ng.
H~ s6 19i d\!ng ella h~ th6ng keOO tum khong duge 006 hon h~ s6 19i d\lllg eho
phep [TI]hghi ph\! hie 2-5
Khi h~ s6lgi d\lllg ella keOO006 hon tri s6 [TI]h ek co bi~n phap eh6ng thk hi~u
qua ( lam lap ao eh6ng thAm ho~e dUng v~t li~u khae) d~ nang eao TIlen.

a

15


•
Vi d~2-3-1. KeOO chiOO mQt M thfmg tum cua mQt he, chua nucrc 006 co so de, b6 tri
keOO OOuhiOO (2-3). H~ sf; tumcua h~ thf;ng: cho Illaql = 1,3I1s;ha; cho mau q2 = 0,6
IIs.ha; toan bQ cae keOOdeu lam bfutg dAt, khong co lap ao bQc. CM dQ tum cho toan khu
tum la tum thuang xuyen.

Ko KC

Hinh 2-3

sf; li~u ve cac keOO:
- N1: Mcr ~i vi tri Ko +500 Clla KC; tum cho Ilia: <01= 50 ha; cho mau: <02= 0 ha;
keOOdai 2,2 Km, co 5 cf;ng Idy nucrc; ddt lam keOOco tiOOthdm nhieu.
- N2: Mcr tiilivi tri KI +700 cua KC ; tum cho Ilia: <01= 70 ha; cho mau: <02= 30 ha;

keOOdiU 3,3 Km, co 7 cf;ng Idy nucrc; ddt lam keOOco tiOOthdm it.
• N3: M& tiiilvi tri Kc Clla KC; tum cho Ilia: (0) = 180 ha; cho mau: <02= 0 ha; keOO
dai 3,6 Km, co 25 cf;ng Idy nucrc; ddt lam keOOco tiOOthdm it.
- N4: M& tiilivi tri Kc cua KC; tum cho Ilia: <01= 380 ha; cho mau: <02= 0 ha; keOO
dai 0,8 Km, chi co 2 cf;ng Idy nucrc VaGN4_1va N4_2;dAt lam keOOco tiOOthdm trung biOO.
• N4-1: M& tiiilvi tri Kc cua N4; tum cho Ilia: <01= 160 ha; cho mau: <02= 0 ha;
keOOdiU 3,8 Km, co 35 cf;ng Idy nucrc; dAt lam keOOco tiOOthdm it.
• N4-2: M& tiiilvi tri Kc cua N4; tum cho Illa: <01= 220 ha; cho mau: <02= 0 ha;
keOOdai 4,4 Km, co 45 cf;ng Idy nucrc; ddt lam keOOco tiOOthdm it.
- Kenh chinh: Chieu diUkeOO3,6 Km; Ddt lam keOOla ddt pha set vira.
Yeu ciu:

Hay tiOOluu lugng thi~t k~, luu higng Ian OOdt,006 OOdt& dAu keOO

chiOO.
Ghi chii: Khi keOO co <0= 50ha S 300ha cho philp tiOO Qtk tiiildAu keOOt1'\ICti~p
qua <0va TJ (rna khong pMi tinh toan theo tan thdt thdm dQCtheo chieu diU keOO)

Bai giai
Cach
1. Tinh toan khong Hip
bang
•
1
,
,
,
De tiOOduQ'c luu lugng thiet ke & dan keOOchiOO, ta can tinh toan xac diOO duQ'c
luu lugng thi~t k~ &dau cac keOOnhanh cdp I; DS tiOOduQ'c luu lugng thi~t k~ & dau keOO
OOanh cdp I, ta can tiOOtoan xac dinh duQ'c luu lugng thi~t k~ & dau cac keOOOOanh cdp

II ...Nhu v~y ta pMi tinh dan tv hiilluu len.

16


1. Kenh N1:
Kenh N I c6 OJ = 50ha
OJ

va 11

:s 300ha,

do d6 ta c6 th~ tinhQtk t(li ddu kenh t1lIc tiep qua

Can cu ph\ll\lc 2-4-1: N 1 c6 chieu dai tinh toan L = 2200m 150ha = 44m/ha, nhuug
c6 56 c6ng lAy mrac bAng 5 100 hon 3, nen kenh thuQc lo(li B; clAtlam kenh thk nuac
nhieu ta tra dugc 11= 0,7
Can cu ph\ll\lc 2-4-2: N I c6 501/5 < Q < 1001/5 va L =2,2km, ta tra dugc 11= 0,80
Thien an toan ta chQn 11= 0,70
Dod6:

ON, =

= 1,3 * 50 = 93 lis
11
0,7

q.OJ

2. Kenh Nz:
Kenh Nz c6 OJ = 70 ha lua+30 ha mau :s 300ha , do d6 ta c6 th~ tinh Qtk t(Ii ddu
kenh kenh t1lIc tiep qua OJ va 11
Can cu ph\l l\lc 2-4-1: Nz c6 chieu dai tinh toan L = 3300m /1 OOha = 33m/ha,
nhuug c6 56 c6ng lAy nuac bfulg 7 100 hon 3, nen kenh thuQc lo(li B; dAt lam kenh thk
nuac it ta tra dugc 11= 0,84
Can cu ph\ll\lc 2-4-2: Nz c6 150 lis < Q < 2001/5 va L = 3,3km, ta tra dugc 11= 0,8
Thien an toan ta chQn 11= 0,8
Dod6:

ONz = q] .OJ, + q2OJ2 _ 1,3 * 70 + 0,6 * 30 = 136 115
11

0,8

3. Kenh N3:
Kenh N3 c6 OJ = 180 ha lfu+O ha mau :s 300ha , do d6 ta c6 th~ tinh Qtk t(li ddu
kenh t1lIc tiep qua OJ va 11
Can cu ph\l l\lc 2-4-1: N3 c6 chieu dai tinh tmin L = 3600m /180ha = 20m/ha,
nhuug c6 56 c6ng lAy nuac bfulg 25 100 hon 3, nen kenh thuQc lo(li B; dAt lam kenh thk
nuac it ta tra dugc 11= 0,76
Can cu ph\ll\lc 2-4-2: N3 c6 250 lis < Q < 3001/5 va L = 3,6km, ta tra dugc 11=
0,86
Thien an toan ta chQn 11= 0,76
Dod6:
ON3

=

q.OJ

11

= 1,3 * 180 = 308 lis
0,76

4. Kenh N4: Kenh N4 c6 OJ = 380 ha lua+O ha mau > 300ha , do d6 ta phai tinh
Qtk t(li ddu kenh d\la vao lUll lugng a cu6i kenh va t6n thAt thk dQc kenh.
f)~tinh dugc Q cu6i kenh ta cdn tinh dugc Q tai ddu kenh N4-1 va N4-z
a. Kenh N4-1:
Kenh c6 OJ = 180 ha lua+O ha mlm :s 300ha , do d6 ta c6 th~ tinh Qtk tIf\lc tiep qua OJ va 11

17


.
can clI ph\ll\lc 2-4-1: N4-1 co chieu dai tinh toan L = 3800m 11~Oha= 22,5~a,
nhung co s6 c6ng lAy nuac bfulg 25 Ian han 3, nen kenh thuQclo(U B; dat lam kenh thiim
nuac it ta tra duQ'c 1] = 0,76
Can ClIph\ll\lc 2-4-2: N4-1co 250 lis < Q < 300l/s va L = 3,6km, ta tra duQ'c 1] =
0,86
Thien an toan ta chQn 1] = 0,76
Dodo:
QN4-1= q.Ol= 1,3* 160 = 274 lis
1]
0,76
b. Kenh N4-2:
Kenh co Ol= 220 ha lua+O ha mau :s 300ha , do do ta co the tinh Qtk t(li trvc ti~p qua Olva 1]

Can clI ph\l I\lc 2-4-1: N4-2 co chieu dili tinh toan L = 4400m 1220ha = 20m/ha,
nhung co s6 c6ng lAy nuac bfulg 45 Ian han 3, nen kenh thuQC lo(U B; dAt lam kenh thAm
nuac trung it ta tra dugc 1] = 0,76
. Can clI ph\ll\lc 2-4-2: N4-2 co 250 lis < Q < 300l/s va L = 4,4km, ta tra duQ'c 1] =
0,83.
Thien an toan ta chQn 1] = 0,76
Dodo:
ON4-2= q.Ol= 1,3* 220 = 376 lis
1]
0,76
e. LIfU hrqng euAi kenh N4:
QCN4= ON4-1+ ON4-2= 274+376 = 650 lis
d. LIfU hrQ'l1~dAu ken~ N4:.
.
,
LUll lugng, dau ,kenh bang lUll lugng cuoi kenh cQng vo; lUll lugng ton that dQC
kenh ( khong co cong lay nuac nao dQc kenh)
LUll lugng thAm dan vi dQc kenh N4:
Qt = 10. AI.Q I-ml
.
BAt lam kenh N4 co tinh thAm trung binh, tra ph\ll\lc 2-2 duQ'c Al = 1,9 ; ml = 0,4
Qt = 10* I ,9* (0,65)1-0,4= 14,7 IIs.km
LUll lugng dAu kenh N4:
QN4 = 650+ 14,7*0,8 = 6621/s
5. Kenh ehinh
a. LUll lugng chua k~ t6n thAt dQc k~nh chinh
Qot= ONI+ ON2+ ON3+ ON4= 93 + 136 + 308 + 662 = 1199 lis
LUll lugng thAm dan vi dQc kenh chinh :
Qt = 10. AI.Q I-mt
BAt lam kenh chinh co tinh thAm trung binh, tra ph\ll\lc 2-2 duQ'c Al = 1,9 ; ml =

0,4
Q, = 10*1,9* (1,2)1-0,4= 21,3 IIs.km
b. LUll lugng dAu kenh chinh
QKC= 1199+ 3,6*21,3 = 12751/s

18


6. Ki~m tra 1')h cua hf thang
H~ th6ng kenh co che dQtum Iiidilng thai nen ta co
=

w,

=

L qiroi _
Q

W

1')h

1,3*(50+ 70+ 180+ 380)+0,6*30
1275

H~ th6ng co ro < 2000 ha, tra ph\ll\lc 2-5 ta dugc
Kenh dilln boo v~ di~u ki~n ch6ng thfun

[1')]h

= 0 71
'

= 0,7 < 1')h =0,71

each 2. Tinh toan theo cach I,p bang
B'ang 2•.2 B'angtJ'nh II1U Iuqng'd'au k-enh em
h' h N
L

Di~n tieh tum (ha)

(km
1

N
Nt
N2
N3
N.
N'.l
N •.2

)

OlUla

2

3

COrnall

4

q (l/s.ha)

ro

qlua

5

6

.
30
710
680
50
1,3
50
0
1,3
70
30
100
1,3
180

0
180
380
0
380
160
1,3
160
0
220
0
220
1,3
bang tinh:
C6t 8: Vai kenh tinh Q theo 1]: la

3,6
2,2
3,3
3,6
0,8
3,8
4,4
Ghi chu

qrnau
7

-

0,6
0,6
0,6

0,6
0,6

Q.
(Qot)

1')

Al

m1

Qt~v

Qt

Qtk

lis

10

II

I/S.km
12

lis

9

13

14

0,4
.

21,2
.

76

1275
93
136
308
662
274
376

lis
8

1199
65

109
234
650
208
286

-

1,9

0,70
0,80
0,76

.
.

.

..

.
.

-

1,9

0,4

14,7

12

0,76
0,76

-

.

.
.

.
.

.
.

Qtt: LlnIlu(J7lg thifc

-

d cua

.
-

kenh; Qtt = qlua *CIJ[ua +

qmim *lUmau

Vai kenh linh Q theo t6n thdt d(lc kenh: la Qo': LlnI Iur;mg chua ki t6n tMt d(lc
kenh (bang t6ng IlnI IU(J7lgcua cac kenh nhanh cua kenh dang tinh toan)
C6t 9: 1]:, H~ s6 l(J'id7,mgcua kenh, tra phl,l/l,lc 2.4.1 va phl,l/l,lC 2-4-2 va chr;m Iri
s6 nh6 dd thidt ki
C6t 10, 11: Al va ml: Cac h~ s6 dd tinh t6n tMt tMm d(lc kenh Qt, Ira phl,l/l,lc 2.
2; (chi cdn tra va tinh khi kenh kh6ng cho phtfp tinh Q theo h~ s61(J'idl,lng 1])
C6tI2: Q'ilv=IO.A1QI.ml
. C6t 13: Q, = Q tilv.L( L la chi€u dai kenh . km)
C6t 14: Qtk = Q,/1] vai kenh cho phtfp tinh Qtk Irifc tidp theo 1] ho(lc Qtk = Qtt+ Q,
vm kenh khOng cho phep tinh Q theo h~ s6 l(J'idl,lng 1])

2.3.2.

L\flI

chqn dl}d6c day kenh i va thiet ke dlfirng ml}'cnwc trong kenh

1. L7,rach(ln d6 d6c day kenh i

DQ d6e day kSnh co anh huang quan tn;mg d~n khil nang lilln vi~e eua kSnh. DQ
d6e i Ian se giilln dugc kieh thuac m~t cAtngang kSnh, tranh duge bili liing trong kenh
nhung I~i lilln giiun khil nang tum l\f chily cua kenh, v~ t6e dong chily ehily 16'0 co th~
lilln xoi 16 kSnh... dQd6e i nho thi nguge I~i.Ngow ra dQd6c day kenh con co anh huang
16'0 d~n kh6i lugng dilo dApkenh. Vi v~y khi chQn dQ d6e day kSnh dn thOa man nhiing
di~u ki~n sau:
- T6n thit ddu nuae theo ehi~u dili kSnh khong 16'0.
• Khong sinh bili liing, xoi 16 long kSnh.

19


- Kh6i Iugng dao d~p keOO006.
.
_ Vi~c xay dgng clIng triOOtren keOOkhong g~p tru ng\li Ian va khong qua ton kiOO
phi xay dgng.
De I\fll chQn d(l d6c day keOOcM yeu elin cu vao d(l d6c dia hi~ dQc keOO, Iugn~
phu sa Clla nuac trong keOO, lUll Iugng Clla keOO. Khi 'I\fll chQn d(l doc day keOO co the
tham khao OOihlgggi Y dum day:
- Khi dia hinh tuyen keOO di qua co d(l d6c Ian va dong chay trong keOOco Iugng
phu sa Ian co the chQn i = 1/2000'" 1/2500.
.
- D6i vm keOOdfut nuac til h6 chua, khi dia hiOOtuy(\n keOOdi qua khong d6c lfun
co the chQn i = 1/3000'" 1/5000.
- Khi dia hinh tuy(\n keOOdi qua vUng d6ng bfulg, dia hinh tuung d6i bfulg phfulg
co the chQn i = 1/5000'" 1/15.000.
Noi chung khi keOOco lUll Iugng 006 thi nen chQn i thien lan, keOOco lUll lugng
Ian thi chQn i thien 006.

2. Thiit ki duang mile nuue thih ki trang kinh
a. Xlie dinh mile nuue kh6ng chi tum til ehtiy ella kinh
M\lc nuac kh6ng che tum t\f chay la m\lc nuac kh6ng che cAn thi(\t de dam bao
dieu ki~n tum t\f chay cho keOOduqc nhieu ooAt.
* Coo d(l m\lc nuac t\li dAu m(lt keOOchan ret xac diOOtheo cong thuc:
V'ElKCR
= A,,+ hr + l.i +L\IIi
(2-10)
Ao : Cao d(l m~t ru(lng (d\li di~n

cho khu tum) cAn tum t\l chay.
hr
: Chieu sau lOp nuac m~t
ru(lng. Vm ru(lng Iua co the lAy A KC B
hr = 10 +I5cm; l.i : T6ng t6n
~
C
D
thAt dQc duemg Clla keOO ( I, i la
NZ-l
M
chieu dai va d(l d6c day keOO
E
tiOOtoan).
L\IIi : T6ng cac t6n thAt
Q
e\lc b(l qua cac cong triOO tren
Kenh chan r€t
keOO(neu co).
Cao d(l m\lc nuac cua Hinh 2-4. Sa dOtinh toan cao d~ ml!c nuac tren kenh tucri
keOO cAp tren ~i dAu keOO OOlinh
cAp dum xae diOOtheo cong thuc:
V'x = V'ElKCD
+ \IIElK
(2-11)
V'DKCD: M\lc nuac kh6ng ch(\ tum t\f chay 0 dAu keOOcAp dum.
L\IIElK: T6n thAt C\lCb(l qua c6ng dAu keOOcAp dum.
Cao d(l m\lC nuac t(li dAu m(lt keOObAt ky xac diOOtheo cong thUc:
V'ElK=V'x + Di.ij +L\IIi
(2-12)

V'DK: Cao d(l m\lc nuac t(li dAu keOOtiOOtoano Vi d\l t(li diem A ho(ic B, C, D tren
hiOO(2-4).

20


Vx (m) : Cao dQ m\IC nu&c t~ mQt diem x ciJa k8nh. Diem x co the duc;rcchQn la
diem cu6i clla k8nh ho~c cr dAu mQt k8nh nIulnh nao do ... (do nguCri thiSt kS chQn). Vi d\!:
Mu6n tinh m\Ic nuac t~ dAu k8nh N2 ta co the chQn X la diem M ho~ P ho~ Q
Lljjj (m): T6ng t6n thAt dQc duimg ciJa dO(ll1kenh tinh ill dAu k8nh dSn diSm X ciJa
k8nh tinh toan ( I;, ij la chi~u dai va dQ d6c day k8nh ( dli chQn ) Clla rung dO(ll1k8nh trong
dO(ll1k8nh tinh toan).
Lljlj (m): T6ng cac t6n thAt C\!CbQ qua cac cong trinh tr8n k8nh ciJa k8nh ho~c
dO(ll1k8nh tinh toan .
Vi~c chQn t6n thAt CQtnucrc qua cac cong trinh tr8n k8nh ph\! thuQc vao rAt nhi~u
YSu t6:Lo~ cong trinh, chi~u dai, luu luc;rng...va cM ySu d\Ia vao kinh nghi~m. De co the
chQn chinh xac han thuimg phai tinh toan thllY I\ICde thiSt ke sa bQ rung cong trinh; sa bQ
co the tham khao ph\!l\!c I ciJa TCVN 4118-85 ho~c tham khao s6 li~u kinh nghi~m sau:
C6ng ngAro: IjI = (7 + 20) cm
C6ng lu6n dai 15 + 20m: IjI = (15 + 30) cm ho~c 160 han
cAu mang dai 15 +- 20m: IjI = (10 + 20) cm
cAu qua k8nh (khi co lam can dong chay): IjI = (5 + 10) cm
NSu chQn t6n thAt cQt nuac qua cac cong trinh tr8n k8nh theo TCVN 4118-85 ho~c
theo s6 li~u kinh nghi~m nhu tr8n can luu y rfutg: Cac trj s6 chQn duc;rcchi la sa bQ; mu6n
kSt lu~ vi~c chQn co chinh xac hay khong dn phai thong qua tinh toan thllY l\Ic C\!the.
* Trinh tv xac dinh m\Ic nuac kh6ng ch~ tum tv chay:
Khi xac dinh m\Ic nuac kh6ng chS tum tv chay, truac h~t cAn chQn duqc diem dl;li
di~n cho tUng khu tum ( diem de tinh A,,). Tuy vao d~c diem cua rung khu tum co the
chQn I ho~c nhi~u diem dl;lidi~n de tinh, sau do tinh dfut dAn 18n cac k8nh cAp tr8n cho d~n
dAu k8nh chinh. Diem cAn tinh dfut 18n la diem dAu cac k8nh va t~ cac vi tri co b6 tri k8nh

cAp dum ho~c crhl;lluu Clla d6c nucrc hay b?c nuac Clla k8nh.
Sau khi dli tinh vm mai k8nh, chQn truimg hc;rpchotrj s6 160 nhAt cr dAu k8nh de
thi~t kS. Sau khi chQn duqc m\Ic nuac thiSt kS cr dAu k8nh chinh, ta cAn kiem tra kha nang
tum t\I chay cho tAt ca cac k8nh chua tinh toan n~u chua khfulg dinh duc;rcbfulg dinh tinh.
M\Ic nucrc kh6ng ch~ tum tv chay duqc tinh toan va chQn sau khi chQn dQ d6c day
k8nh i, nhung no co quan h~ gful bo vm dQ d6c i; khi dQ d6c i 160 thi kha nang tum t\I
chay a vimg thuc;rng luu tang 18n, khi dQ d6c i nho thi nguqc Il;li( duimg m\IC nuac trong
k8nh bao gio cfing song song vm dQ d6c i); vi V?y khi tinh toan rna m\IC nucrc kh6ng chS
tum tv chay khong dam bao thi cAn chQn Il;lii va tinh toan I~.

b. Thih ki iJuimg ml,tcnuac thiit ki trang kenh
Duimg m\IC nuac trong k8nh quan trQng nhAt la duimg m\IC nuac thiSt k~ ( duimg
m\IC nuac khi k8nh tai luu luc;rngthiSt kS). Co duimg m\Ic nuac thiSt kS ta d~ dang suy ra
duimg m\Ic nuac max va duimg m\IC nucrc min trong k8nh.
M\Ic nuac kh6ng chS tum t\I chay la mQt can cu quan trQng nhAt de thiSt kS duimg
m\IC nuac thi~t kS trong k8nh.
Khi thiSt kS duimg m\Ic nuac thi~t k~ cAn dam bao cac yeu sau:
- De dam bao kha nang tum tv chay cao nhAt cho kenh, duimg m\Ic nuac thiSt kS
trong k8nh 10ilng duqc thAp han m\Ic nuac kh6ng chS tum tv chay.
- Khili luc;rngdao dap k8nh nho.

21


- Dam bilo d~ vi~c xaydgng cong trinh tren kenh duqc th$lgi,
d~ bi~t la cong
trlnh thao nu6'c d~ boo v~ kenh, tranh kenh bi nuac ( mua)chliy vao se lam kenh bi xoi 16',
bi bAi lAp.
- Di~u ki~n thi cong thu~ 19i, vi d\l tul~n
kenh co da thi tranh kenh bi dilo sau.

Khi dB.co duemg m\lC nuac kh6ng che tuOOt\l chily, vi~c thi~t k~ duemg m\lc nuac
thi~t k~ dn giill quy~t vAn d~ quan trQng nhAt la : " Co nen nang day kenh cao len (tinh
ti~n len) d~ giam ~6i lugng dao d~p kenh hay khong? Nang cao len bao nhieu?". Khi
nang day kenh len can luu y cae yeu cau khae nhu dii neu tren.
Sau day la m(\t s6 ggi y khi thi~t k~ duemg m\lc nucrc thi~t k~ trong kenh:
- Nen chQn duemg m\lc nuac thi~t k~ trong kenh tuang img vOOm\lc nuac kh6ng
ch~ tuOOt\l chily trong nhUng truemg hqp sau:
+ Cac kenh chan r~t, cac kenh nhanh ho~c dO(lllcu6i kenh bAt ky nfun 6' khu tuOO
Clla chUng ( kenh khong con phill dfuI nuac qua khu tuOOkhac)
+ Kenh rna toan khu V\lCxay dgng (gAm ca cong trinh phfu1g.
- Khi dO(lllkenh a thugng luu Clla khu tuOOmil no ph\! trach co dia hinh dQc tuy~n
cao han nhi~u ho~c tuang d6i nhi~u so vOOdia hinh khu tuOOthi chQn duemg m\lc nuac
thi~t k~ trong kenh cao han m\lc nuac kh6ng ch~ tuOOt\l chliy, sao cho kh6i lugng dilo d~p
kenh la it nhAt, dAng thm cAn cM y vAn d~ an toan, thi cong kenh vii vi~c xay dgng cong
trinh tren kenh co lien quan.
D~ n6i ti~p cac dO(lllkenh li~n k~ co cao d(\ chenh d(\t ng(\t, ta dUng b~c nuac ho~c
d6c nuac.
Vi dy. 2-3-2. Tinh cao trinh kh6ng ch~ tuOOt\l chily tai Ko cua kenh chinh m(\t M
. th6ng tuOOnhu hinh (2-5).

Bi~t:
- Di~m Ao chQn d~ kh6ng ch~ 6' cuM kenh N4-2 co cao d(\ Ao = +5,20m
- Kenh chan r~t cu6i kenh N4-2 (cAp nuac cho di~m Ao) dili 250m; d(\ d6c i =

a

1*10-3
- Kenh N4.2 dili 360m, chi
co nhi~m V\I d~ chia nuac vilo cac

kenh chan r~t ( khong co kenh dfuI
cAp duOO)vii khong co cong trinh
tren tren nilo; d(\ d6c i = 1*10-3•
- Kenh N4 dill 600m, co I Ko KC
c6ng luAn dill 30m, 2 c6ng qua
duemg dill 6m; Qtk= 100 lis; d(\
d6c i = 5*10.4
- Kenh chinh:
+Do(lll tir ddu kenh d~n N I
ffioh 2-5.
dill 800m; co I du mling dili
25m; 3 c6ng qua duemg dill 12m;
Qtk= 450 lis; d(\ d6c i = 2*10-4;
+ DO(lll tir ddu kenh d~n N I d~n N4 dili 900m; co 2 cfru mang dill 15m; 2 c6ng qua
duemg dili 10m; Qtk= 320 lis; d(\ d6c i = 4*10-4.

22


DiU giiii
- Tinh cao dQ m\lC nuac 4li dAu kenh chan rlk
VOKCR= A,,+ hr + I.i +LlJlj
ChQn hr =15cm, ta co:
VOKCR= 5,20+ 0,15 + 250*1 *10-3 +0 = 5,40m
- Cao dQ m\lC nuac cuBi kenh N4-2:
Vx = VOKCD+IJIOK
ChQn tan thtlt qua cBng dp nUlJCcho kenh chan r~t IJIOK=5cm; ta co
Vx = 5,40 + 0,05 = 5,45m
- Cao dQ m\lc nuac dAu kenh N4-2:
VOK= Vx + Di.ii +LlJlj

Kenh khong co cong trinh tren kenh nfto lam tan thtlt nuac, do do
VOK= 5,45 + 360*1 *10-3 = 5,81m
- Coo dQ m\lc nuac cuBi kenh N4:
V N4CK= VOKCD+IJIok
ChQIi tan thtlt qua 1 cBng dAu kenh N4-2 1ft7 cm; ta co:
VN4 CK= 5,81 + 0,07 = 5,88m
- Cao dQ m\Ic nuac dAu kenh N4:
VN4 OK= V N4CK + Ddi +LlJlj
ChQn tan thdt qua (c6ng qua c6ng 1u6n (dfti 30m): 25cm; 2 cBng qua dU6m: lOcm; ta co
.
.
VN4_OK
= 5,88 + 600*5*10-4 + 1*0,25 + 2*0,10 = 6,38m
- Cao dQ m\lc nuac kenh chinh tai vi tri N4:
VKCN4= V N4OK+ IJIOK
ChQn tan thdt -qua c6ng dAukenh N4 1ft10 cm; ta co:
V KC.N4= 6,38 + 0,10 = 6,48m
- Cao dQ m\lC nuac kenh chinh t{livi tri N I:
V KC Nl = V KCN4 + Di.i; +LlJlj
DO(lIl kenh tu N, d~n N4 dai 900m; co 2 cAu mling dfti 15m; 2 c6ng qua du10m; Qtk= 320 lis; dQ d6c i = 4* 10-4.
•
ChQn tan thdt qua m6i cAu mling: 20cm; tan thdt qua m6i c6ng qua duta co

VKC Nl = 6,48 + 900*4*10-4 + 2*0,2 + 2*0,10 = 7,44m
- Cao dQ m\!c nuac 4li dAu kenh chinh:
V KCOK= V KC Nl + Lli.ii +LlJlj
DO(lIl ill dAu kenh chiflh d~n N, dfti 800m; co 1 cAu mling dai 25m; 3 c6ng qua

duChQn t6n thdt qua m6i cAu mling: 20cm; t6n thdt qua m6i c6ng qua duta

co

23


Ghi eM: Viec chQn t6n thAt CQtnuac qua cac cong trinh nhu tren chi! y~u d\la vao
kinh n~ern, nen tri s6chQn chi la tuong d6i; vi v~y vm rnQt de bili ~g nay co the se co
nit nhieu dap s6 khlic nhau va v&nco the coi tAt ca la dUng.

2.4. THIET Kt MAT CAT NGANG, DQCCUA KtNH
2.4.1. L\fll chlln dang
, mit cit ngang kenh, dOxoiii mai kenh
1. Cae dl;mg m(it cat ngang kenh ha thuUng g(ip (hinh 2-6) .

..-~

..-'..- ..~'f

.

..".-

a) m~t ciit hinh thang-kllnh dllt

.

..

He

t6ng

.

c) m~t cih chiI nh~t- kllnh M t6ng
Gidngngang
rnangdan
Giada
~'f~

I I

.-(1."..(1."'<-1'

c_':J
b) rnii-tciit hinh thang - co lap ao bQc

..(I. ~

c_':J

d) rn~t clit hinh paraMn - kllnh n6i

Hlnh 2-6. Mgt 56 dl)Ilg m~t ciit ngang kllnh ha
- Kenh ddt m~t c~t hinh thang ( hinh 2-6a): Kenh dAt m~t c~t hinh thang la 10(li
dugc sir d1)l1grQng rill nhAt trong tAtca cac 10(l1kenh lam bfulg v~t lieu khac do viec xay

d\lDg don gian, kinh phi re; sira chfra, nang cAp don gian ... d ~c bi et I a c ac k enh nh o.
- Kenh dAt co lap ao ch6ng thdm, rn~t c~t hinh thang ( hinh 2-6b): Khi dAt lam
kenh ( dAt nguyen th6 lam n~n kenh ho~c dAt d~p ) co khli nang ch6ng thdm kern kenh dn
dugc gia c6 them rnQt lap ao ch6ng thdm bfulg be tong ( tdm lat ho~c d6 t(li ch6 ), da g(lch
lat ... D(lDg kenh nay cling dugc sir d1)l1gnhieu do co kha nang ch6ng thdm, ch6ng xoi t6t,
kinh phi xay d\lDg cling khong d~t I~, viec tu b6 kenh hang nam cling it t6n kern hon

~~~~~_b~;~~~

kenh dAt.
- Kenh bfulg be tong, da g(lch xay, rn~t c~t chfr nh~t ( hinh 2-6c): D(lDg kenh nay
cling la rnQt ~g kenh co lap ao bQc. Cac ~g nay co kha nang ch6ng thdm, ch6ng xoi
t6t, it bi hu hong ( do S(lt rnai, xoi 1&b&... ), viec tu b6 kenh hang nam cling it t6n
kern ... Tuy nhien cac d(lDg nay kinh phi xay d\lDg d~t, nen no chi thuOng dugc lIng d1)l1g
vm cae cong trinh quan trQng hoi;ickhi kenh di qua vUng dan cu, do thi hoi;ic khi kinh phi
xay d\lDg d6i dao.
Lam kenh d(lDgrni;itc~t chfr nh~t giam dugc dien tich chi~m dAt Clla kenh.

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- KeOO d\lllg m~t cdt hiOOparabOn ( hiOO 2-6d) ho~ d\lllg hiOO cong, hiOO da giac
khac: Cac lo\li miy thuOng lam bang be tong c6t thep ( xi mang lum thep ) nit mong nen
con gQi Ia cAu mling vo mongo PMn chAn nuac Clla keOO do lam nit mong nen khong c6
kha nang chiu b,rc theo phuong dQc (vi v~y phlii lam gia do mling). KeOO<4uig nfly thuOng
lam n6i tren m~t dAtnen giam duQ'c OOi~udi~n tich chi~m D\lIlg keOOmiy chi thuOng duQ'Csu d\lIlg cho m(lt dO\lll keOOmill d6 khi can thi~t,
vi d\! khi keOO can vuQ't qua m(lt canh d6ng triing, r(lng do vi~c xay d\ffig phuc 4lP, yeu
cAu triOOd(l ky th~t cao, kiOOphi ddt.
2. each z,.,rach(Jn d(mg mi;itcdt va wjt lifU iii xay dlPlg kenh

Khi l\lll chQn d\lllg m~t cdt keOO, can can phlin tich kY cac ~c di~m Clla timg d\lllg
'm(it cdt dii mo tli tren va di~u ki~n thgc t~ Clla keOOd~ c6 th~ chQn duQ'c d\lllg m(it cdt hQ'P

Iy.
V~t li~u xay d\ffig keOOchil y~u la dAt tl;lich6 (ddp). Khi dQc tuy~n keOOkhong c6
d~t d~ ddp ( da, soi ) thi mm nghi d~n vi~c dimg lo\li v~t li~u khlic d~t, vi d\!: be tong, da
gl;lchxay ... ho(ic chuyen cha d~t cac vimg llin c~ tuy~n keOOd~n d~ ddp.
Khi d~t lam keOO ( d~t nguyen th6 va d~t ddp ) la d~t t6t ( dti cuang d(l va ch6ng
thk t6t ) thi nen chQn keOOla keOOd~t. Khi dAt lam keOOcUOng d(l t6t OOung tinh ch6ng
thk kern OOu d~t cat, pha cat. .. thi ciing nen chQn keOO la dAt OOung can lam them 16p
phil ch6ng thk. Lap phti ctia keOOcling c6 th~ d4ng cho keOOdAt ch6ng thk t6t d~ tang
cUOng kha nang chOng x6i la, tang cuOng tioo ben vting lau dai cho keOO, giam chi phi
nl;lOvet, sua chua keOOhang nam ...
Khi danh gia tiOOthk ctia d~t c6 th~ tham khlio ph\! b,IC2-1 (cho h~ s6 thk trung
biOO( gAn dling ) ctia m(lt s6 lo\li d~t).
Khi chQn d\lllg m~t cdt keOO la hiOO thang ho~ khi mlii ngolii Clla keOO la hiOO
thang, can pMi chQn d(l xolii cho tUng mlii keOO(mlii trong va mlii ngoai) hQ'PIy.
D(l xolii mlii keOOc6 anh hUOng chti y~u d~n khli nang 6n djnh ctia mlii va kiOO phi
. xay d\ffig keOO. Khi chQn d(l xolii mlii keOO can cu vao chi~u sau nuac Clla keOO, lUll
lugng keOO, d~t lam keOO,keOOc616p bao v~ hay khong ...
Khi chQn m c6 th~ tham khao ph\! h,IC2-6.

a

2.4.2. Tinh toan, chfln kich thU'cYcm~tcit ngang kenh
1. Thiit 1d mi;itcdt !rUt cua kenh
a. Khai quat chung
Thi~t k~ m~t ciit um cho keOOla tiOOtolin va
chQn chi~u r(lng day b va chi~u sau c(lt nuac h ctia
m~t ciit ngang keOO khi keOO thao vm lUll lugng

thi~t k~ ( hiOO2-7).
Sau khi chQn duQ'c d(l d6c day keOO i, d(l
ffinh 2-7. M~t ciit u<1tthi€t k€ cua
xolii mai trong m, can cu v~t li~u lam long keOO ta
xac diOO d(l OOam long keOO n ( ph\! I\!c 2-10) d~
kenh hinh thang
th~ ti~n hanh tiOOtoan va chQn kich thuac m~t ciit um cho keOO.
Truac khi ti~n hilnh tiOOtoan chQn b, h chiOO thuc can chQn ( sa b(l) tri s6 b ho~c
h. Tri s6 b thuOng chQn theo kiOOnghi~m. N~u chQn truac tri s6 h, sa b(l c6 th~ chQn theo
cong thuc sau:

25