I. Xac dinh cac thong s6 ban ddu
3.Trim ra, trim bang
Dong chay quatran ra, tr3.n bang thuang la dong chay qua d~p tran dinh rQng va luon la dong chay tv do. Vi v~y ta co dUng cong thuc (3-2) d6 tinh. Khi tinh co th6 lAy h~ s6 co h~p ngang e=1 d6 tinh.
4. Caumang
Gilio trinh nay chi trinh bay cho cAu mling d<mgho, m(it c~t ch1i nh~t (hinh 3-6)
__ .D_ID_R_'_,I'1/ 1/ ~1'11L~ Zl DK L f .DTDR2
H'mh 3-6. ScIdO tfnh tmin thuy l~ mang dai
Khi tinh va chQn khdu di~n cho cAu mling, truoc h8t cAn phan bi~t mling ng1ln va mling dai.
Mling ng1ln la mang co L ::;(8+1OH) Mling dai la mling co L >(8+1OH)
(3-5) Khi mang ngtln, vi~c tinh toan tuang tg nhu c6ng ho.
Khi ffiang dai ta coi dong chAy qua mang ill dong chAy lien hi~ giita 3 cong trinh nhu sau: d~p tran dinh rQng 0 Clm vao (BTBRI) chAy vao mQt dO{lllkenh (BK) 18.than mang, sau do chAy vao d~p tran dinh rQng 0 cua ra ( BTBR2) ( hinh 3-6).
Trinh tg tinh toan d~ chQn B, h: Co nhi~u cach tinh, giao trinh nay chi trinh bay mQt cach thuang dUng nhu sau:
- ChQn coo trinh day B], de) d6c i Clla mang: cao trinh day thuang chQn coo han day kenh 0 cua vao khoang 5 -;. I Ocm d~ giam bUn cat troi vao mango Be) d6c i thuang chQn i =1/400 -;. I/!OOO sao cho v~ t6c trong mang v = 1,0 -;.1,5m/s. Tinh H va cao trinh
B2•
- Tinh toan chQn B, h theo dO{lllkenh: DUng cong thirc C(Jban cua dong d~u trong kenh ho (Q =roc.JRi ) d~ tinh va chQn B, h. Khi tinh nen dUng phuang phAp thu dAn d~ tinh
Trinh tg: gia thi~t Zl =5 -;. !Ocm, tinh h =H - Z], sau do tinh thu dAn d~ xac dinh B.
Co B tinh toan, ta ti~n hllnh chQn B. B thuang chQn chdn den dm va b6 tri thu m(it c~t ngang mango N~u thAy B chua hQ'PIy chQn I~ Zl ho(ic ca coo trinh B], de) d6c i va tinh
I~i.
- Ki~m tra Q theo kha nang thAo 0 cua vao: DUng cong thirc d~p tran dinh re)ng chAy ng~p d~ tinh ZOI ( cong thirc 3-3a):
Z _ Q2
01 - 2B2h22
<Pn g
Trong cong thirc tren d1ib6 qua h~ s6 co hC(pngang E
<potra ph1,ll1,lc(3-3) theo h~ s6 lUll lugng m (ph1,ll1,lc2-2) ho(ic co th~ lAy gAn dUng <po=0,95 -;. 1,0
Kh. 'nh1tI co teo' h' b' qua -y~
2g
Neu ZOI xAp xi Ho- h thi khA nang thao 0 cua vao la dam bao.
Neu ZOI Ian han Ho- h nhi~u thi kha nang thao 0 cua vao la thira; khi do ta nen nang cao cao trinh day mang len cho phil hQ'P.
. Neu ZOI nh6 han Ho- h thi kha nang thao 0 cua vao la thieu; khi do ta nen h~ cao cao trinh day mang xu6ng de nang cao Zl len cho dam bao
Ngoai ra co th~ chQn I~ i vii tinh chQn I~ B theo dO{lllkenh vii tinh toan kiem tra - Ki~m tra Q theo kha nang thao 0 cua ra :ciing dung cong thlrc (3-3a) de tinh:
Q2
Z02=--~-
E2<p~B2h22g (adsbygoogle = window.adsbygoogle || []).push({});
Khi tinh co the lAy E= I ; <po= 0,87 -;. 0,90 de tinh nhung chli Y Iii khong duqc b6
y2
qua ---M. 2g
Chenh lech muc nucrc th"c te 0 ciIa ra:., . Zo2tt = D2+h-MNHL+ V~ = f)l-iL+h-~
MNHL+ V~; VM=Q/Bh 2g
Neu Z02 xtlp xi Z02tt thi kha nang thao 0 ciIa ra Iii dilm bao. Qua trioo tlnh toan ket thuc.
Neu Zo2 16'nh(JllZo2tt nhi~u thi ill nang thao 0 ciIara Iii thiIa; Khi do ta co the tang dQ dac i len ( B se giilm xuang) vii thiet ke I~i til dau.
N eu Z02 006 h(JllZ02tt thi khii nang thao 0 ciIa ra Iii thieu; khi do ta neIi gilim dQ dac i ( B se tang len) va thiet ke I~i tir dAu.TrnOng hQP cuai cling, neu mang vful khong du khli nang thao thi cAn phlii thiet ke I~i keOOtum (tiing cheOO I~ch m\lc nucrc thUQ'Ilgh~ lUll len).
an!!so i~uVI !J 3-3-3
IT D(ic trung Q Cao trioo M\lC nucrc
(m3/s) day (m) (m)
1 Kenh thuqnl! luu 9,90
Max 10,68 Thiet ke 10,60 Min 10,45 2 Kenh h<lluu 9,70 Max 10,52 Thiet k8 10,44 Min 10,29
3 Luu luqng kenh
Max 0,60
Thiet ke 0,50
Min 0,30
Vi d\l 3-3-3 : Hay tiOOtoan chQn khAu di~n cho mQt cAu mang dful nucrc tren keOO tum co m(it c~t ngang hiOOcM OO~t.
Biet:
- Cao trinh day cang : + I O,OOm;
- Chi~u dliinguOn~ cang L = 25,Om; "
- CiIa vao tU(Jllg doi th~, nguOng tron, co wOng clinh thang, thu hc;p dan. - DQ OOilmcua rnang n = 0,015
sa li~u khac cho 0 bang
B' JZ- °d
Khi tiOOb6 qua lUll toc tm gan 0 ciIa vao. Bai giiii
1. ChQn trn6ng hQP tiOOtmin
KeOOthUQ'Ilgh~ I~ co m(it c~t OOuOOau,nen cheOO I~ch m\lC nucrc thUQ'Ilgh~ lUll khi keOO thao vm cli 3 cap lUll lUll IUQ'IlgIii OOuOOau, vi v~y ta chi cAn chon trnOng hQP keOOthao Qrnax=0,6m3Is de thiet ke khAu di~n cho mang la duo .
2. Ch(,m cac thong sa ban dAu
- DQ d6c day mling i = 1/400 = 0,0025; - Chenh I~ch cQt nuac acua vao Zl = 10cm; Ta tinh duQ'c:
H = 10,68 - 9,95 = 0,73m; (adsbygoogle = window.adsbygoogle || []).push({});
L = 25,Om> 10H = 0,73*10 = 7,3m nen mling la mling dai. Sa d6 tinh nhu (hinh 3-7)
__ D_ID_R_I_;I. DK t DTDR2
v L ~/
MNTI. ~ Zl Z2'"
Hinh 3-7
Xae dinh cae thong s6 lien quan khac:
h = H - 0,09 = 0,73- 0,10 = 0,63m;
D2 = Dl - i.L = +9,95 - 1/400*25 = +9,89m hn = 10,52 - 9,89 = 0,63 m;
Z2 = D2 +h - MNHL = +9,89 +0,63 - 10,52 = 0,00 m
3. Tinh tolin va chQn 8 theo kha nll.n¥thao Clla dOii\llkenh , . Dimg cong thtrc ca blin cua dong deu trong kenh h6' va phuong phap thu dan de tinh 8
- CQt nuac trong mling: h = H - 0,10 = 0,73- 0,10 = 0,63m; - Gia thi~t 8 = 0,75m Ta tinh duQ'c: ro = B.h = 0,75*0,63 = 0,473 m2 X= 8+ 2h =0,75 + 2*0,63 = 2,01m R = ro/X= 0,473/2,01 = 0,235m C = .!.R1/6 = _1_.0,235116= 52,37 n . 0,015 Q = roc.JRi = 0,473*52,37 ~0,235 * 0,0025 =0,60m3/s VM= Q/ro = 0,60 10,473 = 1,27m/s
Q = 0,60 = Qmax= 0,60 m3Is, v~y vi~c gia thi~t 8 = 0,75m la dung V~ t6c dong chay trong mling VM = 1,27m/s thuQc ph(ll11vi pM hgp.
ChQn 8: Ch(;m 8 = 0,75m de thi~t k~ cho mling ( ciing co the chQn ch~ 8 = 0,80m)
4. Kiem tra kha nang thao cho d~p tran 6' cua vao
86 qua cQt nuac luu t6c t6i gdn nen ta co cac thong s6 thlJc t~ t(li cua vao nhu sau: Ho= H = 0,73 m; ZOltt= Zl = O,IOm; h = 0,63m;
Ta cAn ki€m tra cheOO I~ch cQt nuac ZOltttren co dam Mod€ cl'ra vito thao du luu luong Qrnaxtheo yeu cAu hay khong ( Tinh ZOlho~ Q theo cong thuc tinh Q d~p tran vii so'sanh v&i ZOlttho~ Qrnax d€ k8t I~)
• TiOO Zol theo kha nang thao Clla d~p
Ctmg co cua vao tuong d6i th~, ngu5ng trim, co tu<'mg canh thing, thu h~p dAn; tra ph\ll\lc 3-2 vii ph\ll\lc 3-4 ta dugc m =0,34; cpn= 0,90. .
Do cheOO I~ch cQt nuac thugng h~ luu trong mang 006, nen co the xac diOO dong chay qua d~p tran Iii chay ng~p rna khong cAn ki€m tra ch8 dQ chay.
Y&i ~p triin diOOrQng chay ng~p, ta co:
. Q' 06'
ZOl= , " - , ,', - O,IOlm
CPnBh 2g 0,9.0,75.0,63.19,62
ZOI= 0,101 '" Zoltt = 0, 10m : CI'ravitO dil kha nang thao theo yeu cAu. 5. Ki€m tra kha nang thao cho d~p triinacua ra
E>~ptran acua ra khong co ngu5ng va khong co co thu h~p ngang, tra ph\ll\lc 3-3 vii ph\ll\lc 3-4 ta xac diM dugc m = 0,385; CPn= 1,0; Ta tiOO dugc cheOO I~ch cQt nuac yeu cAu Z02 :
Z = Q' 0,6' - °082m
02 cp~B'h' 2g 1'.0,75'.0,63'.19,62 ' CheOO I~ch cQt nuac th\IC t8acua ra Z02tt :
Y' 1,27'
Zo2n=Z2+-.M. =00+ -- =0080m
2g ' 1962, ' (adsbygoogle = window.adsbygoogle || []).push({});
Z02 = 0,082", Z02tt= 0,080m : Cua ra dil kha nang thao theo yeu cAu.
K8t I~: Ch(;m B = 0,75m va cac thOng s6 khac OOudil chQn ta th~y: Mang dil kha nang ill nuac theo yeu cAu, v~ t6c trong mang trong ph~ vi pM hgp, cua vao cao hon day keOOthugng d€ co the giam bUn cat vao mang ... Y~y ta the chQn cac thong s6 dil chQn d€ thi8t k8 cho mango
5. C6ngngdm
C6ng ngAm thu<'mg g(l.pIii c6ng dAu keOO,c6ng qua du<'mg, c6ng tieu.
Dong chay qua c6ng ngAm co the Iii d~g co ap, ban ap vii khong ap (hiOO 3-8). Giao trinh nay chi trinh My tinh toan cho tru<'mghgp c6ng chay co ap ( hinh 3-8a,b). Khi thi8t k8 c6ng ngAm ta nen thi8t k8 c6ng Iii d~g chay co ap d€ t~ dvng h8t khil nang thao cuac6ng.
- Sa db tinh toan c6ng chay co ap nhu hinh(3-8a, b)
- E>i€uki~n d€ c6ng chay co ap: H 2: (1,14 -+- 1,18)d va hn 2: d ho(l.c H 2: (1,14 -+- I, 18)d vii hn <d nhung co nuac nhily trong c6ng vii chi€u sau nuac nhay he" >d
Khi H 2: (1,14 -+- 1,18)d va h. <d va kh6ng co mrac nhily trang c6ng haiJc co mrac nhily trang c6ng nhrmg he"<dc6ng sechay ban tip.
Khi H < (1,14 -+- 1,18)d c6ng se chtiy kh6ng tip.
• Chi tieu c6ng co ap chay ng~p : hn 2: d • Phiin bi~t c6ng dili, ng~n:
/// a) a) ~-'- /////// -+ L ;~ /// b) ~E4i /////// /// -+ L MNHL n /// 'r- MNHL n -/////// -f----L----,r- ./ / / MNTL H /// d) MNHL n /// ,r- //.///// L /// c)
Hlnh 3-8. Sadodong chay qua c6ng ngAm
a) Chay co ap, ng~p; b) chay co lip,lI!do; c) chay ban ap; d) chay khOng ap
Khi c6ng chay co ap la ngfut co th€ bo qua t6n thAt dQc duang d€ tiOOtoan cho dan gian.
- Cong thuc tiOO:
Q=IJ.ro~2gZo (3-5)
ro: men tich m\it dt um Clla 6ng c6ng.
IJ.:he s6 luu IUQ'llgcua c6ng ngfun co ap.
1 1
Il-~==- ~~~~~~=
- ~l+ I.~-~l+ I.~c+I.~d
L~c:T6ng t6n thAt C\lCbl} cua c6ng, gAm: t6n thAta cua vao ( khong co tan thAt cua ra), t6n thAt qua lum chfut rac.
Tan thAt C\lCbl}a cua vao co th€ lAy theo bang PL3-8-6 ph\l I\lC 8; tan thAt qua lum chfut rac ( tru6'c c6ng) lAy theo m\lC 3 ph\ll\lc 8.
Ngoai ra khi c6ng ngfun la c6ng <tAukeOO OOanh tum co huang dong chay vao c6ng vuong goc ho\ic gAll vuong goc vm keOO cAp tren thi con phai xet d~n tan thAt khi chay re OOanh.V m c6ng d&u keOO tum 000, t6n thAt C\lCbl} chi co a cua vao, d€ dan gian trong tiOOtoan va thien an toan co th€ chQnL~c= ~v=0,5 d€ tiOO.
L~d:T6ng tan thAt dQc duang cua c6ng ngfun, xae diOOtheo m\lC 1 ph\ll\lc 8 ho\ic co th€ tiOOtheo cong thuc sau: