I: ngu5ng tran; 2 va 3: 6ng do lip; 4: voi xa
c. Tim tung dQ duemg cong MNN t\li di6 m
L' .' .•....! '. i.•....! • i' " .•....!+16 = 20 m trong truemg hqp gi8ng hoim chinh ?
. - .. - .. ~NlJOt:T1I'IR . Giili:
---~---~~---+14a) Day la gi8ng khong ap khong hoan chinh
vi gi8ng khoan xuyen qua tiing cat thO thfun
nucrc, day gi8ng chua ch\lffid8n tAng cach
nucrc ben dum. Cac thong sf, suy ra til hinh
ve nhusau:
H=(+14)-(+4)= 10m
[=(+14)-(+9)- S =5 -2=3 m< 1/3H
S=X(S+l) ~2=X(2+3) hay: X =2/5 = 0,4 ~ Y = 1,6
hay Ha = 1,6(2 + 3) = 8 m. Suy ra: ha = Ha - S ~ 8 - 2 = 6 m. + Tim B : h~s6khong hoirn ehinh:
B =~ I tha -I = [3~2.6-3 = 0,783.
ha ha V'6 6_
+ Tim ban kinh imh hu6ng R: R = 2S~Ha .k =2.2.J8.12,5 = 40 m + Tinh lUllluqng giSng khong hoirn ehinh, QKhc:
I 366K(H2 _h2) 2 _ 2
Q =' a a B = 1,366.12,5.(8 6) .0,783 = 143,87m3/ng.d
Khe IgR -Igr Ig40-lgO,I
b) Tru6ng hC)'pgiSng hoirnehinh, vi day giSng khoan dSn tfulgelich nuae ben dum. + Tim ban kinh imh hu6ng R: R = 2S.JH.k = 2.2.JIO.12,5 = 44,7 m
+ h=H-S=IO-2=8m.
+ Tinh lUllluqng giSng hoirn ehinh:
2 2
1,366K(H - h) 1 366 125 (102 _82)
Q = =' . ,. = 232m3/ngd.
he IgR-Igr Ig44,7-lgO,1
.e. Tim tungdQ y:
y = h2 + 0,73.Q.(lgx -Igr) = 82 + 0,73.232.(lg20 -lgO,l) = 9,75 m.
k 12,5 .
~ 3.6. Dong thdm too cae cong trinh tieD thoat DIrac ilon nim ngang.
Cae cong trinh tieu thoat nuae dan nfun ngang co kenh va M th6ng kenh thoat nuae hoan ehinh va khong hoirn chinh.
3.6.1. Kenh dan thoat nuac hoirn ehinh.
a) LUll luqng dan vi q, dong ng~m ehAy d~n tir m(\t phia ba kenh (hay rlinh tieu) tren 1m dai kenh:
H2_h2
q=k-- -(m3/ngd) (3-101)
2R
b) Luu luqng Q, dong ng~m chAy d~n tir m(\t phia ba kenh (hay ranh tieu) tren B (m) dai kenh :
Q=B.k H2 - h2 (m3/ngd) (3-102)
. H-h '
Neu gQi 1= R' I 1ftgradien dong ngam thi :
c) LUll IUlll1gQ, dong ngdm chay d~n ca hai phia ba kenh (hay ranh tieu) tren B (m) dfti kenh 1ft: (3-105) (3-104) (3-103) (m) (m) hay Q=B.k(H +h)I hay 2 h2 Q=B.kH - R
Trong do: H 1ftb~ day tdngchua nu6'c
h 1ftdi) sau lOp nu6'c trong kenh (riinh tieu)
R la chi~u ri)ng vimg ilnh hu6'ng clia kenh thOlit, dugc tinh til mi)t
mep biYkenh.
d) Tung di) duang cong m\Tcnu6'c dugc tinh theo c6ng thuc:
~h2 2q.x
y= . +T
~ 2 x(H2 _h2)
.y= h +----
R
Trong do: x 1ftkhoilng cach tu mep kenh d~n ti~t di~n xac dinh y q 1ftlUll IUlll1gdon vi
R
/
Hinh 3.27 Kenh don thmit nuac holm chinh
R
3.6.2.Kenh dan thoat nuac kh6ng hoan chinh.
D6i vai kenh kh6ng hoan chinh (day. kenh chua ch\ffi1 den tAng cach nuac ben dum), vi~c tinh toan lUll luqng co xet den b€ day lap nuac co hi~u qua (phan b6 ben tren tAng chUa nuac) Ho :
a) LUll luqng dan vi q, dong ngl1m chliy den tir mQt phia biYkenh (hay ranh tieu) tren 1m dai kenh:
(3-106)
(3-107)
c) LUll luqng Q, dong ngl1m chliy den ca hai phia biYkenh (hay ranh tieu) tren B (m) dai kenh la:
Q=B.k H~; h~ hay Q =B.k(Ho +ho)1o (3-108)
V.,<Y1I Ho-ho I I'd' d'. thA
0 = R ,0 a gra len ong am
Trong do: Ho la b€ day tl1ng chua nuac co hi~u qua (ho~t dQng) ho la dQ sau lap nuac ho~t dQng trong kenh (ranh tieu) R la chi€u rQng vimg anh huang cua kenh thoat, duqc tinh . tir mQt phia biYkenh.
3.6.3. H~th6ng kenh thoat nuac hoan chinh.
Khi cAntieu thoat nuac cho mQt vimg ta co thS dung h~ th6ng kenh, it nhAt hi hai kenh b6 tri song song. H~ th6ng g6m hai kenh se c~td(rt dong ngl1m chliytm khu V\fC gifta chung. Nhu v~y van d€ tieu nuac &khu Y\lC nay th\l'c chAt Ill.tieu tho at luqng nuac mua itgAm xu6ng (W, m/ngd) dS gift cho mgc nuac ngl1m & do kh6ng dang len cao.
a) Luu luqng dan vi q, dong ngl1m chliy den tir hai phia biYkenh (hay ranh tieu) tren 1m dll.icua m6i kenh Ill.:
I~ ~ (3-112) (3-111) (3-110) (m) q=W.L (m3/ngd) (3-109)
b)Luu luqng Q, dong ngAm chily d~ntilhai phia bakenh (hay ranh tieu) tren cit chi~u diti (B) m6i kenh Iii:
Q=W.L.B (m3/ngd)
c) Khoang each giua hai kenh, xac dinh theo cong thtrc:
L=2(H-S)~~
d) DQ hit m\lC nuac ngAmbe nh~t, quan sat th~y akhoitng giua hai kenh :
HWL2
S . =H- h +-- (m)
mm 4k
• w,
L
CHUONGIV: