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2 Bé N«ng nghiÖp vµ Ph¸t triÓn n«ng th«n viÖn khoa häc thñy lîi sæ tay kü thuËt thñy lîi phÇn 2 c«ng tr×nh thñy lîi tËp 4 Cöa van vµ thiÕt bÞ ®ãng më Kh¸i niÖm chung vÒ cöa van trong c«ng tr×nh thñy lîi Thñy lùc cöa van Cöa van mÆt Cöa van s©u ThiÕt bÞ ®ãng më cöa van biªn so¹n GS. TS. Tr-¬ng §×nh Dô - PGS. TS. NguyÔn §¨ng C-êng Nhµ xuÊt b¶n n«ng nghiÖp Hµ Néi - 2005

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  • 2

    B Nng nghip v Pht trin nng thn

    vin khoa hc thy li

    s tay k thut thy li

    phn 2

    cng trnh thy li

    tp 4

    Ca van v thit b ng m

    Khi nim chung v ca van trong cng trnh thy li

    Thy lc ca van

    Ca van mt

    Ca van su

    Thit b ng m ca van

    bin son

    GS. TS. Trng nh D - PGS. TS. Nguyn ng Cng

    Nh xut bn nng nghip H Ni - 2005

  • Mc lc 5

    Mc lc

    Li gii thiu 3

    Mc lc 5

    Chng 1. Khi nim chung v Ca van trong cng trnh thy li 11

    1.1. Vai tr nhim v ca ca van 11

    1.2. Cu to ca van 11

    1.3. Phn loi ca van 11

    1.4. Chn loi ca van cho cng trnh 12

    1.4.1. Vng ven bin ng bng sng Cu Long 12

    1.4.2. Vng ven bin Trung B 13

    1.4.3. Vng ng bng Bc B 13

    1.4.4. Ca trn p trn h cha v p dng vng Trung du v min ni 13

    1.5. B tr ca van trong cng trnh 13

    1.5.1. i vi cng h 13

    1.5.2. i vi cng kn 14

    1.6. Lc v t hp lc tc dng ln ca van 14

    1.6.1. Lc tc dng 14

    1.6.2. T hp lc 14

    1.7. Vt liu lm ca van 15

    1.7.1. Thp 15

    1.7.2. Gang 18

    1.7.3. ng 18

    1.7.4. Cao su 18

    1.7.5. Vt liu tng hp Composite 19

    1.7.6. B tng ct thp 19

    1.8. Nhng vn cn l u trong thit k ca van 19

    1.9. Ph ng php tnh ton 21

    1.9.1. Phng php phn tch h kt cu phng 22

  • 6 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1.9.2. Phng php phn tch h kt cu khng gian 28

    1.9.3. Mt s quy nh trong thit k kt cu ca van 35

    1.10. Mt s ca van nghin cu v ng dng 35

    1.10.1. Ca van phng 35

    1.10.2. Ca van cung 36

    1.10.3. Ca van Clape trc di (ca sp) 36

    1.10.4. Ca van Clape trc trn 36

    1.10.5. Ca van hnh qut 36

    1.10.6. Ca van mi nh 36

    1.10.7. Ca van tr ln 36

    1.10.8. Cc kiu ca quay trc ng 36

    1.10.9. Cc kiu ca quay trc ngang 36

    1.10.10. Cc kiu ca van t ng thy lc iu tit trn knh 36

    1.10.11. Cc kiu ca van u tu 36

    Chng 2. Thy lc ca van 37

    2.1. Khi nim chung 37

    2.2. Nng lc x n c 37

    2.3. p lc n c tc dng ln ca van 42

    2.3.1. Ca van phng 42

    2.3.2. Ca van cung 50

    2.3.3. Ca van qut 53

    2.3.4. Ch thy lc khi trn qua ca sp 53

    Chng 3. ca van phng 55

    3.1. Ca van phng 55

    3.1.1. u nhc im ca ca van phng 55 3.1.2. Cc b phn chnh ca ca van phng 55

    3.1.3. Cu to ca cc b phn chnh 56

    3.1.4. Ti trng v lc tc dng ln ca van phng 59

    3.1.5. Cc kiu ca van phng 61

    3.1.6. Kt cu phn p ngng khe van v giong kn nc 65

    3.2. Ca van cung 67

  • Mc lc 7

    3.2.1. u nhc im ca ca van cung 67

    3.2.2. Nhng kt cu chnh 67

    3.2.3. Xc nh v tr ca dm chnh 70

    3.2.4. Cc kiu ca van cung 71

    3.2.5. Xc nh p lc nc tnh tc dng ln ca van cung 73

    3.2.6. Tnh trng lng bn thn ca cung 76

    3.2.7. Tnh lc nng h 76

    3.3. Ca sp (ca Clape trc di) 77

    3.3.1. c tnh c bn 77

    3.3.2. Ca sp iu khin bng c kh 77

    3.3.3. Ca sp t ng bng i trng 79

    3.3.4. Ca Clape phao (gi tt l ca sp phao) 81

    3.4. Ca Clape trc trn 82

    3.4.1. Cu to 82

    3.4.2. Nguyn l lm vic 82

    3.4.3. Phm vi p dng 82

    3.5. Ca qut 83

    3.5.1. Phm vi ng dng 83

    3.5.2. Cc loi ca qut 83

    3.5.3. iu kin nng v h ca qut 86

    3.5.4. Kt cu ca qut 89

    3.5.5. iu khin ca qut 90

    3.6. Ca van mi nh 91

    3.6.1. Phm vi ng dng 91

    3.6.2. Cc kiu ca van mi nh 91

    3.6.3. Lc nng v h ca mi nh 92

    3.6.4. Kt cu ca van mi nh 95

    3.6.5. Thit k v iu khin ca van mi nh 95

    3.7. Ca van tr ln 96

    3.7.1. Phm vi s dng 96

    3.7.2. Cc kiu ca van tr ln 97

    3.7.3. Kt cu ca ca van tr ln 97

  • 8 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    3.7.4. Xc nh trng lng bn thn v lc nng ca van tr ln 98

    3.7.5. My nng ca van tr ln 100

    3.8. Ca van gin quay 100

    3.9. Ca van cnh ca t ng 102

    3.9.1. Xut x ca van cnh ca t ng 102

    3.9.2. Cu to 102

    3.9.3. S b tr ca van cnh ca t ng 104

    3.9.4. Nguyn l hot ng v tnh lc ng m 105

    3.9.5. Ch vn hnh ca ca van cnh ca t ng 109

    3.9.6. Cc b phn chnh ca ca van v khung cha van 110

    3.10. Cc kiu ca bn lch trc ng t ng v bn t ng 114

    3.10.1. Cu to 114

    3.10.2. Nguyn l lm vic t ng 115

    3.10.3. Phm vi p dng 115

    3.11. Cc kiu ca van trc ngang 116

    3.11.1. Ca phn vin (mt phn t hnh trn) 116

    3.11.2. Ca van Amil 117

    3.11.3. Ca van cung i trng t ng iu tit mc nc 119

    3.11.4. Ca van bn quay trc ngang 119

    3.12. Ca u tu 122

    3.12.1. Cc loi ca u 122

    3.12.2. Ca ch nhn 124

    Chng 4. ca van su 137

    4.1. Mt s vn cn ch khi thit k ca van su 137

    4.2. Ca phng su 137

    4.2.1. Cu to 137

    4.2.2. Ti trng v lc tc dng ln ca 139

    4.2.3. Phm vi s dng 140

    4.3. Ca van cung su 140

    4.3.1. Cu to 140

    4.3.2. Mt s tnh ton c bn 142

    4.3.3. Phm vi ng dng 144

  • Mc lc 9

    4.4. Van a 144

    4.4.1. Cu to 144

    4.4.2. Ti trng v lc tc dng 145

    4.4.3. Tnh sc bn ca v v a 146

    4.4.4. Phm vi ng dng 147

    4.5. Van cu 147

    4.5.1. Cu to 147

    4.5.2. Phm vi s dng 148

    4.6. Ca Van hnh kim 148

    4.6.1. Cu to v vn hnh 148

    4.6.2. Phm vi s dng 149

    4.7. Van cn 150

    4.7.1. Cu to 150

    4.7.2. Tnh bn 150

    4.7.3. Tnh lc ng m 151

    4.7.4. Cc hnh thc b tr v phm vi s dng 151

    4.8. Ca van hnh tr 151

    4.8.1. Cu to v vn hnh 151

    4.8.2. Xc nh ng sut v n nh ca v hnh tr 154

    4.8.3. Tnh lc nng h 155

    4.8.4. Phm vi p dng 155

    4.9. Chn kiu ca van d i su 155

    Chng 5. Thit b ng m ca van 157

    5.1. c im, cu to v phn loi thit b ng m ca van 157

    5.1.1. c im ca thit b ca van trn cng trnh thy li, thy in 157

    5.1.2. Cu to chung ca thit b 157

    5.1.3. Phn loi v phm vi ng dng 158

    5.2. My ng m kiu vt ai c 160

    5.2.1. Nguyn l my ng m kiu vt ai c 160

    5.2.2. u, nhc im ca thit b ng m kiu vt ai c 161

    5.2.3. Tnh ton thit b vt ai c 162

    5.2.4. My ng m kiu vt dng cho ca van su 164

  • 10 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    5.3. My ng m kiu dy mm 165

    5.3.1. Kt cu chung ca my ng m kiu dy mm 165

    5.3.2. u, nhc im ca thit b ng m kiu dy mm 166

    5.3.3. Tnh ton cc thng s c bn 167

    5.4. Thit b ng m bng xilanh thy lc 173

    5.4.1. Cu to chung v nguyn l hot ng 173

    5.4.2. u im ca xilanh thy lc 175

    5.4.3. Nhc im ca thit b ng m bng xilanh thy lc 175

    5.4.4. Tnh ton cc thng s c bn thit b ng m xilanh thy lc 176

    5.5. H thng iu khin ng m ca van 177

    5.5.1. T ng iu khin, t ng ha bng in v in t my tnh 178

    5.5.2. iu khin t xa 178

    5.5.3. T ng bng thy lc 178

    Ph lc. Mt s thit b ng m ca van 179

    Ti liu tham kho 182

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    Chng 1 - Khi nim chung v ca van... 11

    Chng 1

    Khi nim chung v Ca van trong cng trnh thy li

    Bin son: GS. TS. Trng nh D

    1.1. Vai tr nhim v ca ca van

    Ca van l mt b phn rt quan trng trong cng trnh thy li. Ca van c lp t vo cc khoang ca cng trnh thy cng cng trnh thy li thy in. Ca van cng c th t trn mt, di su. Nhim v ca ca van l ng gi nc v m tho nc theo yu cu t ra cho cng trnh: ly nc ti, cp nc pht in, thot l, gn triu, tiu ng, iu tit mc nc, ly nc mn nui trng thy sn...

    Hiu qu ca cng trnh thy li, thy in c m bo nh thit k t ra khi ca van c vn hnh t tin cy nh quy trnh vn hnh ra.

    Nu vic vn hnh ca van c s c th dn n khng nhng tn hi ln cho cng trnh thy li, thy in m cn gy tc hi cho sn xut i sng ca vng h du. Mt

    s v v p gy thit hi ln n , M l do kt ca van trn x l.

    1.2. Cu to ca van

    - Phn chuyn ng gm bn mt, cc dm ph, cc dm chnh, cc bnh xe ln, giong chng thm, phn thit b nng gn vi ca van.

    - Phn c nh gm cc kt cu ta t tr pin, p trn, kt cu chng thm v phn thit b nng gn vi cng trnh. Vic vn hnh ca van c th nh vo my nng c, in, xilanh thy lc hoc hon ton li dng sc nc - thng c gi l ca van t ng thy lc, hoc va li dng sc nc va c h tr ca c in th c gi l ca van bn t ng thy lc. Ngy nay mt s cng trnh vic vn hnh ca van mt s nc c t ng ho in t, iu khin t xa rt hin i.

    1.3. Phn loi ca van

    Ca van c th phn loi theo v tr t: Ca van trn mt, ca van di su; theo hnh dng kt cu: Ca van phng, ca van cung, ca van tr, ca qut, ca mi nh, ca bn quay...; theo hnh thc tho nc qua ca van: Ca van nc trn trn mt, ca van nc chy pha di; theo hnh thc chuyn ng: Ca van chuyn ng thng ln xung, ca y ngang, ca quay trc gia, trc trn, trc di; theo cch ng m ca

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    12 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    van: Bng sc nc (t ng thy lc v bn t ng), bng thit b c kh v bng in; theo tnh cht vt liu: Ca van thp, ca van b tng ct thp, ca van vt liu tng hp.

    Ngoi ra theo nhim v c th chia ra: Ca van vn hnh (s dng cho khai thc cng trnh); ca van sa cha (dng thay th khi sa cha ca van vn hnh); ca van s c (dng x l khi c s c xy ra); ca van thi cng s dng trong khi thi cng v trong s c th dng lm ca van d phng, ca van sa cha v ca van s c.

    1.4. Chn loi ca van cho cng trnh

    Vic chn loi ca phi cn c vo tnh cht, nhim v v iu kin t nhin ni xy dng cng trnh p ng tt nht cho nhim v cng trnh v cng tc qun l khai thc.

    1.4.1. Vng ven bin ng bng sng Cu Long c im ca vng ny l bn nht triu. a s cc cng c nhim v ngn mn

    gi ngt, thau chua ra phn v ly nc triu ngt trong mt s thi gian, ngoi ra c mt s cng li cn ly mn phc v nui trng thu sn khi chuyn i c cu sn xut. Do vy cng lm vic 2 chiu: c th m gn triu tiu ng v cng c lc m

    ngc li ly triu. vng ny c th p dng 4 loi ca sau:

    a) Ca van cnh ca t ng thy lc (CVCCT)

    y l loi ca van hin c ng dng rng ri nht v c nhiu u im hn cc loi ca van khc. N c ng m nh p lc nc v lc lch trc nn khng th dng ca van ny iu tit mc nc.

    b) Ca van cung

    t c s dng v vic ng dng ca van cung t ng gn triu tiu ng i hi phc tp, nu iu khin bng c in thng thng th nhn lc phi tc trc

    thng xuyn trong ma tiu l. nhng cng ng m t mi nm mt s ln th c th dng ca van cung.

    c) Ca Clape trc di (ca van sp)

    nhng ni ca van c ng 5 - 6 thng v sau m lin tc 5 - 6 thng th c th p dng loi ca ny. V c u im c th lm ca rng 15 30 m.

    d) Ca van phng

    Ca van phng c ng m bng thit b c kh hoc c in, c th dng nhng cng mi nm ch m t ln nhng hin t dng vng ny.

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    Chng 1 - Khi nim chung v ca van... 13

    1.4.2. Vng ven bin Trung B C 2 loi cng:

    - Loi cng thng b chm ngp trong l chnh v nn ng dng ca Clape trc di. ng m nh v khi l v ca van nm st y. Loi ny c th lm khoang rng v cng c th ng dng ca van cnh ca t ng.

    - Loi cng cao khng b chm ngp trong l chnh v v gn bin d b gi bo th c th ng dng ca van cung, van phng, ch ng ng m tho l v iu tit mc nc.

    nhng cng gn bin chu nh hng ca bo, nu ch dng n thun ca van cnh ca t ng th s khng ch ng ngn triu dng v tho l. Bi v loi ca ny

    ch m cng bc c khi chnh lch nh hn 1m. nhng cng ny hoc ch dng ca van cung, hoc va dng ca cung phi hp ca van cnh ca t ng khi l bnh thng th gn triu tiu ng v khi c bo th thm mt s ca cung tho l.

    1.4.3. Vng ng bng Bc B

    a) Vng ven bin chu nh hng ca triu

    y l ni c ch nht triu, yu cu cp nc v tiu l mt cch ch ng.

    y khc xa vi 2 vng trn, cc cng nn p dng ca van cung hoc ca van phng ng m bt k lc no theo yu cu khng ch mc nc trong ng.

    b) Vng ng bng khng chu nh hng ca thu triu

    Cng vng ny nn p dng ca van cung, ca van phng v c th dng ca Clape trc di ch ng iu tit mc nc trong ng bt k thi im no.

    1.4.4. Ca trn p trn h cha v p dng vng Trung du v min ni Thng c s dng ph bin l ca van cung hoc ca van phng cng c th

    p dng ca van Clape trc di. y cng c th dng ca qut t ng thy lc, khi m nm trong bng p khi ng ca c nng ln.

    1.4.5. Cng trnh x su hoc ly nc di su

    Thng c s dng ca van cung hoc ca van phng. Nhng cng nh ly nc su c th dng van cn hoc van kim.

    1.5. B tr ca van trong cng trnh 1.5.1. i vi cng h

    a) Loi khng c tng ngc

    nhng cng trnh nc thng lu lun ln hn h lu, ca c b tr thin v pha sau tng an ton cho cng v lt trt. nhng cng ngn triu thng ca van t gia m bo n nh c hai chiu.

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    14 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    b) Loi c tng ngc gim chiu cao ca van

    i vi ca van cung nht thit phi b tr sau tng ngc, cn ca van phng th c th b tr trc hoc sau ty .

    1.5.2. i vi cng kn C th b tr ca van ming vo, gia hoc cui cng.

    1.6. Lc v t hp lc tc dng ln ca van 1.6.1. Lc tc dng

    - p lc thy tnh.

    - p lc thy ng. - Trng lng bn thn.

    - Lc qun tnh.

    - p lc sng.

    - p lc gi.

    - p lc chn khng. - Lc va ca tu thuyn, vt ni.

    - p lc bn ct. - Lc ma st.

    - Lc ca thit b ng m.

    - Lc ng t.

    - Ti trng th.

    1.6.2. T hp lc Khi tnh ton thit k cn phn ra cc t hp lc tnh ton:

    a) T hp chnh

    - p lc thy tnh. - p lc thy ng. - Trng lng bn thn.

    - Lc qun tnh.

    - p lc sng. - p lc gi. - p lc chn khng. - p lc bn ct. - Lc ca thit b ng m.

    - Lc ma st.

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    Chng 1 - Khi nim chung v ca van... 15

    b) T hp c bit

    Gm t hp chnh v thm cc lc:

    - Lc nng khi ca b kt.

    - lc va ca tu thuyn v vt ni.

    - Ti trng do ng t

    - Ti trng th.

    1.7. Vt liu lm ca van 1.7.1. Thp

    a) Phn loi thp

    Theo thnh phn ho hc:

    - Thp cacbon: lng cacbon C < 1,7%. Khng c cc thnh phn hp kim khc.

    Chia ra thp cacbon thp, lng cacbon C t 0,09 0,22%, l thp xy dng ch yu; thp cacbon va lng cacbon C t 0,25 0,5% dng cho ch to c kh; thp cacbon cao lng cacbon C t 0,6% l thp dng c.

    - Thp hp kim, chia ra: thp hp kim thp vi t l cc nguyn t hp kim di 2,5% l thp xy dng; thp hp kim va v thp hp kim cao s dng lm thp dng cho ch to c kh v dng c.

    b) K hiu thp

    - Thp cacbon thp: Theo cch t tn ca Lin X c thp cacbon thp c cc s hiu CT0, BCT2, BCT3, BCT4 theo th t t t n nhiu cacbon. Ch B l ch nhm thp c m bo v c tnh v thnh phn ho hc.

    - Thp hp kim thp: Theo cch t tn ca Lin X c th hai s u ch phn

    vn cacbon; ch ci Nga ch tn cc thnh phn hp kim: mng gan G, silic C, crm X, niken H, ng , vanadi f, bor P, mlipen M, titan T, nhm IO, nit A; con s sau ch lng phn trm (lm trn) khi qu 1%.

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    16 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Bng 1-1 chim 1 trang

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    Chng 1 - Khi nim chung v ca van... 17

    Bng 1-2 Bng 1-3 chim 1 trang

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    18 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1.7.2. Gang Nhng chi tit ca ca nh bnh xe ln, bnh xe c, ci ca chu p lc nh hn

    60 kG/cm2 c th dng gang xm v gang chng mi mn theo.

    Bng 1-4. Tnh nng c hc ca gang

    Ko

    Gang cng Brinell Gii hn n hi

    kG/mm2

    Gii hn ph hoi

    kG/mm2 dn ko t

    %

    Ct kG/mm2

    Gang xm

    Gang rn gc:

    - peclit

    - ferit peclit

    - ferit

    240

    280

    200

    175

    -

    42 - 46

    38 - 44

    32 - 40

    25

    58 - 75

    50 -58

    42 - 48

    1 - 2

    5 - 10

    10 - 18

    34

    68

    48

    37

    Bng 1-5. Cng tnh ton ca khi c bng gang xm (GOCT 1412 - 79)

    Cng tnh ton MPa ca khi c bng gang xm Trng thi ng sut

    C 15 C 20 C 25 C 30

    Ko ng tm v ko khi un

    Nn ng tm v nn khi un

    Trt

    p mt t u

    55

    160

    40

    240

    65

    200

    50

    300

    85

    230

    65

    340

    100

    250

    75

    370

    1.7.3. ng Dng lm bc trc bnh xe, trc quay ca ca hoc ng trt dng ng vi

    [s] = 150 kG/cm2 c du bi trn v [s] = 140 kG/cm2 khng c bi trn.

    1.7.4. Cao su Dng lm giong chn nc ca cao su Sao vng H Ni cc ch tiu cn t:

    - Gii hn n nh khi dt t: 180 kG/cm2

    - dn di tng i khng b hn 5 ln

    - dn di d khng ln hn: 40%

    - Sc khng rn nt khng b hn: 70 kG/cm2.

    - cng theo Shore khng b hn: 60

    - n hi: 45 65%.

    Cao su dng lm ca van: Hin nay sn xut trong nc.

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    Chng 1 - Khi nim chung v ca van... 19

    1.7.5. Vt liu tng hp Composite Hin ti ca van bng thp bc composite c ng dng kh ph bin v ca

    van hon ton bng vt liu composite cng c ng dng nhiu cho vng ven bin ni c chnh lch ct nc thp nhng cha tng kt v cha c hng dn thit k. Tnh cht c l ca vt liu composite nh sau:

    - ng sut ko Rk = 2700j = 675 kG/cm2

    - ng sut nn Rn =1600j + 670 = 1070 kG/cm2

    - ng sut un Ru = 6500j - 525 = 1100 kG/cm2

    Trong : j = 0,25.

    1.7.6. B tng ct thp Ca van bng b tng ct thp dng v mng c ng dng lm ca van t ng

    mt s cng trnh vng ven bin c kt qu tt; mc b tng 300 c dng ph gia ha do nn b tng t cht lng cao.

    1.8. Nhng vn cn l u trong thit k ca van

    1.8.1. Phi chn loi ca van ph hp vi tnh cht v nhim v cng trnh p ng c yu cu t ra trong qun l khai thc, ph hp vi iu kin ch to lp t, vn hnh, sa cha bo dng thay th v ph hp kh nng u t kinh t k thut. iu cn ch nht khi chn loi ca van l tin cy trong vn hnh ng m thc hin nhim v iu tit mc nc lu lng do yu cu sn xut ra.

    1.8.2. Tnh ton ca van c v bn v n nh i vi nhng lc v ti trng c bn tc dng ng thi v kim tra ng sut khi c s tc dng ca cc ti trng c bit v t hp ca chng vi nhng lc c bn. Thng c tnh theo trng thi gii hn th nht v trng thi gii hn th hai.

    1.8.3. Trong tnh ton s b, vic chn chiu cao mt ct dm chu lc phi xut pht t iu kin vng cho php, tnh theo cng thc:

    [ ]25

    f . .24 E.2.a

    = s

    ; (1-1)

    trong :

    f - vng tm ca nhp dm;

    - nhp tnh ton ca dm chu lc, cm;

    a - khong cch t trng tm mt ct tnh ton ca dm chu lc n mp

    dm (cm); c ly a = (0,75 0,65)hct (hct - chiu cao ca mt ct dm);

    E - m un n hi, i vi thp, E = 2100000 kG/cm2;

    [s] - ng sut cho php (kG/cm2) ca vt liu lm ca van.

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    20 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    vng cho php ln nht ca cc dm chnh ca ca van khng c vt qu:

    Ca hot ng thng xuyn Ca lm vic tm thi

    + i vi dm c: 1

    .750

    1

    .500

    + i vi dm gin: 1

    .1000

    1

    .700

    Cc dm ph vng tnh ton khng vt qu: 1

    .250

    .

    1.8.4. Trong trng hp cc dm chu ti trng khng u, i vi lin kt c khi

    ctc h 5> v i vi cc lin kt gin khi ctc h 2> th phi tnh ca van theo trng thi

    xon. y c l khong cch gia cc dm.

    1.8.5. Kt cu ca van phi thun tin cho vic ch to, lp rp, quan trc theo di, sa cha, thay th cc b phn v c tin cy cao trong vn hnh.

    1.8.6. Hnh dng mp di ca van phi thun cho dng chy, khng b cn v khng gy mch ng p lc ng k v hin tng kh thc mp ca van.

    1.8.7. Phi m bo hnh dng khng pht sinh chn khng i vi cc ca van cho nc trn qua v m bo thng khng kh di lp nc trn .

    1.8.8. Phi chn c vt liu lm ca van v bin php bo v ca van bn trong mi trng chua mn, m t...

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    Chng 1 - Khi nim chung v ca van... 21

    Thu thp v phn tch ti liu

    iu tra, nghin cu, th nghim m hnh hoc thc t

    Chn loi hnh ca van

    B tr

    Tnh ton

    Thit k

    Tnh trng lng v lc ng m

    Lp phng n cng ngh

    V hnh

    Ch to

    Lp t

    Vn hnh th

    Lp li nhiu ln

    Tholun tnghp kthut

    Vn hnh chnh thc

    1.8.9. Trnh t cng tc t thit k n vn hnh ca van.

    1.9. Ph ng php tnh ton

    Ca van thy cng l vt kt cu khng gian ba chiu, nn v nguyn tc phi dng h kt cu khng gian tin hnh phn tch tnh ton. Nhng bi v trc y k thut tnh ton cha pht trin, nu lm nh vy trn thc t gp rt nhiu kh khn. Do trong thit k cng trnh mt thi gian di dng phng php phn tch h mt phng tnh ton. Tc l phn tch kt cu khng gian ca ca van thnh nhiu kt cu

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    22 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    phng c lp, sau tin hnh tnh ton ring bit. Lm nh th s thun tin cho cng vic tnh ton, nhng cng a n nhiu sai s khng ph hp vi thc t, v vy kt qu tnh ton mang tnh gn ng, khng th phn nh tnh trng lm vic ca ca van mt cch chn thc.

    My nm gn y s dng phng php phn t hu hn cng s h tr ca my tnh in t, gii bi ton kt cu khng gian ca ca van, thc t v thu c kt qu ng tin cy.

    Phn ny gii thiu khi qut hai phng php tnh ton trn.

    1.9.1. Ph ng php phn tch h kt cu phng

    Quan h gia cc cu kin trong ca van thy cng tng i phc tp. y ly ca van phng mt bnh xe c nh, lm v d cho thuyt minh phng php phn tch h kt cu phng (hnh 1-1).

    Bn mt trc tip chu p lc nc v truyn n dm khung bn bn. Ph ti l khu vc gch cho trong hnh, v theo ng phn gc, phn phi khung dm 2 bn. Ph ti ca dm ph nm ngang nh biu th trn hnh (a), (b). Ph ti ca dm ph thng ng, ngoi ngoi lc nc do bn mt truyn n, cn phi chu phn lc gi dm ph nm ngang truyn n, ph ti ca n c biu th hnh (c).

    Phn lc gi ca dm ph thng ng v h lin kt hng ng l ph ti truyn cho dm ch nm ngang, sau khi cng thm p lc nc do bn mt trc tip truyn n, ph ti c biu th hnh (d). Phn lc gi ca dm ch ngang truyn cho dm bn, sau khi cng thm p lc nc do bn mt truyn n, ph ti ca n nh hnh (e). Dm bn da vo trc bnh xe ca bnh xe chnh, v vy p lc nc tc dng ln bn mt cui cng qua bnh xe chnh truyn cho ng ray v kt cu gn trong b tng.

    Bng phng php nu trn ta a mt ca van khng gian phn tch thnh rt nhiu cu kin h phng c lp, sau khi c ph ti vic tnh ton s khng cn kh khn na. Nhng cn phi ch , trn ng giao nhau ca hai cu kin h phng, phi xt cng dn ng sut.

    i vi ca van cung hoc cc hnh thc ca van khc, u c th s dng phng php ny c mt nhm h kt cu phng c gi tr nh kt cu khng gian ban u. Vt kt cu ca nhng h phng ny do bn, dm, ct v thanh ging v.v... to thnh. Phng php phn tch xem ti liu c hc kt cu.

    y ch gii thiu phng php tnh ton bn mt c lin quan ti kt cu ca van m Trung Quc khi bin son quy phm thit k ca van thp, ngi ta i su nghin cu t thc nghim v tnh ton. Qua rt ra cc kt lun sau y:

    (1) Vt liu thp l mt loi vt liu n hi rt tt, lm vic trong phm vi bin dng nh, trng thi ng sut trong bn mt hon ton thng nht vi kt qu ca l thuyt bn mng n hi. Thc nghim cho thy, tin din ton ca cng thc Pakh l cha cht ch, khng th phn nh tnh trng lm vic thc ca bn mt, khng nn tip tc s dng.

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    Chng 1 - Khi nim chung v ca van... 23

    (2) Bn mt trong kt cu ca van c hai tc dng: Mt l trong qu trnh truyn p lc nc, n c tc dng un cong cc b, ng sut ca n c th tnh ton theo bn mng n hi ca gi trn khung dm. Hai l, n li l mt b phn ca khung dm tham gia vi kt cu tng th, ng sut ca n c th xc nh c theo bin cnh ca khung dm.

    (3) ng sut pht sinh ln nht trong bn mt (hay gi l im khng ch ng sut) l im gia ca vi khung 4 bn.

    Theo tnh hnh b tr ca van thng thng, im khng ch xut hin ti im gia ca cnh di khu dm.

    (4) Thc nghim cho thy, bn mt khi i vo giai on lm vic c tnh n hi do, cng tim tng rt ln, phm vi ca khu tnh do c m rng, im khng ch ng sut s nh v cc b. Da vo ng sut cho php ca n tin hnh kim tra cng l thch hp.

    Cn c vo cc kt lun nu trn quy nh phng php tnh ton bn mt nh sau:

    a) ng sut un cc b ca bn mt smx, smy nn cn c vo dng khung bin tnh ton theo bn mng n hi chu ph ti phn b u, cng thc tnh ton nh sau:

    2

    m 2

    kpas =

    d; (1-2)

    Trong :

    p - cng p lc nc ca trung tm khu tnh ton bn mt (kG/cm2);

    a - di cnh ngn ca tnh ton bn mt (cm) tnh t khe hn gia bn mt v dm;

    d - dy ca bn mt (cm);

    k - h s ng sut un ca im gia cnh bn mng n hi. Trong tnh ton c th chia thnh hai loi: im gia cnh di v im gia cnh ngn. Gi tr ca n tra trong hnh 1-2.

    b) Nu bn mt ni lin vi dm , cho php bn mt lm vic vi bin cnh ca dm, rng hu hiu B ca n ly bng tr tng i nh tm c theo cng thc:

    B = x.b;

    B 60d +b1; (thp s 3) (1-3)

    B 50d +b1; (thp s 16)

    Trong : b - khong cch gia dm,

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    24 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1 21

    b = (b +b ); 2

    b1 - rng bin cnh trn ca dm, nu khng t bin cnh trn th bng dy bn bng ca dm;

    x - h s rng hu hiu, xem hnh thc b tr ca dm, tra theo hnh 1-3;

    Hnh 1-1. Tnh trng chu lc ca ca van phng trn mt

    1- bn mt; 2- dm ph ngang; 3- dm ng; 4- h lin kt ng; 5- dm chnh ngang; 6- dm bin; 7- h lin kt sau cnh;8- bnh xe di chuyn; 9- tai ca; 10- bnh xe c; 11- ng ray chnh; 12- ng ray ngc.

    RA 3 B 3 C 3

    gia

    A 1 B 1 A 2 B 2

    Nhn hng E Nhn theo II-II (c) (e)

    Nhn theo I - I Nhn theo hng F

    gia

    (b)(a)(d)

    11

    I I

    I I

    I I

    A 1 B 1

    A 2 B 2

    A 3 B 3

    A 4 B 4

    A 5 B 5

    A 6 B 6

    C1

    C 2

    C 3

    C 4

    C 5

    C 6

    1

    4

    E

    F

    B 1

    B 2

    B 3

    B 4

    B 5

    B 6

    A 1

    A 2

    A 3

    A 4

    A 5

    A 6

    R 2

    R 1

    7

    1210

    15

    5

    7

    5

    432

    5

    51

    8

    6

    9

    3

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    Chng 1 - Khi nim chung v ca van... 25

    0,3

    0,4

    0,5

    0,6

    0,7

    0,76

    1 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

    b/a

    K

    AB

    AB

    AB a

    by

    BA

    A

    B

    Bin c nh

    Bin gi n gin

    im gia cnh di bin c nh

    im gia cnh ngn bin c nh

    x

    mx A my A

    my B mx B

    ( ) .( )

    ( ) .( )

    s = m s

    s = m s

    Hnh 1-2. Tr s K

    0 - khong cch gia im O, i vi dm chng n gin 0 = 1. i vi

    dm chng lin tc, xc nh gn ng theo hnh trn;

    x1 - ng vi hnh m men un dng ng Parabon;

    x2 - ng vi hnh m men un m hnh tam gic.

    c) Khi tnh ton cng ca bn mt, nn a ng sut smx, smy tm c theo un cc b nu trn cng vi ng sut sox tm c theo bn cnh cnh dm (hoc soy).

    ng sut tnh ton szh sau khi cng li nn tho mn iu kin sau y:

    [ ]zh 1,1.s a a ; (1-4) Nu t s chiu di cnh ca bn mt b/a >1,5 m cnh di b tr theo hng trc

    dm (hnh 1-4) th ch cn tnh ng sut ca im A theo cng thc:

    ( ) ( ) ( ) ( )2 2zh my mx ox mx oxAs = s + s - s - s - s ; (1-5)

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    26 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    b

    d

    b

    l 0=0,8l

    l 0 =0,4l

    l 0=0,6l

    ll

    x1

    2x

    0b

    0b

    0

    b2

    1b

    0 2 4 6 8 10 12 14 16 18 20

    0.2

    0.4

    0.6

    0.8

    1

    x

    l0/b

    x1 bx2 b

    Trong : 2 2my kpa /s = d ;

    mx my my0,3s = ms = s ;

    oxs - ng sut un ca dm i vi im A;

    mx my ox, ,s s s - thng nht dng tr tuyt i.

    Hnh 1-3. Tr s x

    Nu t s di ca cnh bn mt ct b/a 1,5 hoc b tr cnh ngn theo hng trc dm (hnh 1-5), ngoi vic tnh ng sut ca im A ra, cn phi tnh ng sut ca im B theo cng thc sau:

    ( ) ( ) ( ) ( )2 2zh my mx oy my mx oxBs = s + s + s - s s + s ; (1-6)

    Trong : 2

    mx 2

    kpas =

    d.

    my mx mx0,3s = ms = s .

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    Chng 1 - Khi nim chung v ca van... 27

    ( )oxM

    1,5 0,5W

    s = x - .

    M, W - m men un v m men khng ca mt ct dm i vi v tr ca im tnh ton;

    mx my ox, ,s s s - thng nht dng tr tuyt i.

    V s dng cng thc (1-5) v (1-6) tnh ton (szh)A, (szh)B tng i phin phc, rt kh b i mt s trng hp tnh ton khng cn thit no mt cch trc quan; ng thi cng do tnh ton phc tp, d sai xt, v th c th i thnh cng thc n gin ha di y (1-7) v (1-8) thay th cng thc (1-4), (1-5) v (1-6).

    iu kin tnh ton vi im A:

    [ ]ox my0,65 0,68s + s a s ; (1-7) iu kin tnh ton vi im B:

    [ ]ox mx0,9 0,8s + s a s ; (1-8) So snh vi cng thc ban u, sai s ln nht bng khong 1,2%.

    Hnh 1-4. Tnh ton ng sut ti im A

    Hnh 1-5. Tnh ton ng sut ti im B

    smy

    smx-sox

    X

    b

    a

    Ang trc dm

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    28 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1.9.2. Ph ng php phn tch h kt cu khng gian

    Kt cu ca van phn tch theo h khng gian c coi trng sau khi my tnh in t ra i kt hp vi phng php phn t hu hn. Phng php phn t hu hn, ng dng trong lnh vc phn tch kt cu ngy nay c s dng rng ri. T kt qu phn tch m xt, n phn nh mt cch tng i st thc trng thi lm vic ca kt cu, ng thi cn x l mt cch t ng, nhanh chng v tiu chun ho rt tt.

    Trong phng php phn t hu hn, c mt vn quan trng l lm sao xy dng c m hnh s ca kt cu phn nh c gi tr nh nhau vi kt cu thc, sao cho mt h kt cu c t do v hn chuyn ho thnh mt h kt cu t do hu hn.

    Thng cn c vo b tr c th ca kt cu phn on xc nh. v vy ngoi vic phi nm vng trng thi lm vic ch yu ca kt cu, cn phi xem xt lm sao cho tnh cht phn t ca kt cu sau khi phn nh phi tng i n gin, d tnh ton quan h c tnh ca phn t.

    V d: i vi kt cu ca ca van phng do bn mt, dm dc, dm ngang v cc b phn khc to thnh, phn tch nh phn tch phng php h mt phng trnh by trn, ng nhin c th xem nh mt loi phng n phn nh.

    Chng qua trong phng n ny tuy xem xt tnh cht lm vic ch yu ca kt cu, nhng tnh cht phn t ca kt cu sau khi phn nh tng i phc tp, kh c th xc nh quan h c tnh phn t ca n. V vy, c th a kt cu ca van tng tng nh mt tm bn c gia cng bi h thng khung dm, cng chnh l mt h kt cu khng gian do bn hai chiu v dm mt chiu to thnh.

    Hnh 1-6. S phn nh kt cu ca ca van phng

    1

    2

    3

    6

    5

    4

    7

    8

    9

    12

    11

    10

    13

    14

    15

  • www.vncold.vn

    Chng 1 - Khi nim chung v ca van... 29

    Nh hnh 1-6 bn mt 1-3-15-13 gn ln dm ngang 1-3, 4-6,..., 13-15, trn dm dc 1-13, 2-14, 3-15 m to thnh t hp kt cu. C th ct ri ton b kt cu ca van theo tuyn trc dc, ngang phn chia thnh rt nhiu phn t bn v phn t dm, do vy m hon thnh qu trnh phn nh kt cu.

    Hnh v cho thy phn t kt cu ca van phng, gm c 8 phn t bn v 22 phn t dm, cc phn t c lin kt li bi cc nt 1, 2,..., 15.

    Khng nghi ng g na, do kt cu l lin tc, trn cc im nt cc chuyn v v ni lc ca cc phn t bng nhau.

    Sau khi chia nh ton b kt cu, cng vic ca bc sau tin hnh phn tch tnh ton tnh nng i vi cc loi phn t.

    Do cc loi phn t ch tip xc vi nhau ti cc im nt. V vy c quan h c bn tc l thm lc trn im nt v chuyn v do lc sinh ra. Quan h ny c th dng cng hoc mm ca phn t din t. Trong kt cu c th dng nguyn l cng o kt hp vi phng trnh hnh hc, phng trnh vt l tin hnh din ton.

    Sau khi tnh c tnh nng ca phn t, c th tin hnh kt hp li kt cu, a kt cu phn nh, theo mt quan h nht nh ti tp hp li, khi phc li din mo nguyn dng ca kt cu. Lc ny cn thit phi tho mn:

    (1) iu kin cn bng - Ni lc tc dng ln cc im nt cn m bo cn bng vi ngoi lc tc dng ln cc im nt.

    (2) iu kin tng ng - Di tc dng ca ph ti v ngoi lc ln phn t, bin dng ti cc im nt (v trn bin) cn phi duy tr lin tc.

    Cn c vo nhng yu t ny, c th vit ra c ton b phng trnh nhiu bin s tm li gii. Quy m nhm phng trnh lun lun rt ln, ch c th gii c trn my tnh in t. Sau khi gii c bin s ca nhng im nt ny, theo tnh nng ca phn t thu c t u, c th tm ra c ng sut v chuyn v ca bt k mt im no trong phn t. Hng mc ny cng do my tnh in t m nhim.

    T c th thy, dng phng php phn t hu hn phn tch kt cu khng gian hon ton ging nh phn tch kt cu siu tnh trong c hc kt cu. Cc bc tin hnh c th quy np thnh:

    Bc 1: Phn chia nh cc phn t kt cu

    Bc 2: Chn bin s ca phn t kt cu v quy lut thay i bn trong n.

    Bc 3: Tnh ton c tnh ca phn t.

    Bc 4: Tp hp tng th hon chnh.

    Bc 5: Tm li gii ca bin s ca kt cu (V d chuyn v v ni lc ca im nt).

    Bc 6: Tnh ton bin s kt cu ca cc im ni b cc phn t (nh ng sut v bin dng).

    V d, phng php tin hnh tnh ca van phng.

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    30 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1 2 3 4

    5 6 7 8

    2 29 10 11 12 13 14

    3 2 2 3 3 315 16 17 18 19 20

    u .x .y .x.y

    v .x .y .x.y

    .x .y .x .x.y y

    x x y xy y x y xy

    = a + a + a + a = a + a + a + a

    w = a + a + a + a + a + a ++a + a + a + a + a + a

    (1) a kt cu ca ca van tin hnh phn chia nh, nh hnh 1-6, ct ra mt mnh nh kt cu t hp ca bn mt v dm, nh hnh 1-7 v ly h to tay phi lm to .

    (2) Dng phng php chuyn v: ly chuyn v ca im nt lm bin s ca kt cu. Dng hm s chuyn v di y (i vi dm x, cho y = 0 i vi dm y, cho x =0)

    (1-9)

    (3) Qua tnh ton thu c ma trn cng ca phn t bn l:

    [ ] [ ]T1 1

    banK C . B . C- - = (1-10)

    Trong [C -1], [B] c xc nh t cng thc (1-11) n cng thc (1-14).

    [C -1] T l biu th ma trn chuyn v tr ca [C -1].

    [ ] 11

    B 0EB

    0 B1

    = - m

    (1-11)

    Hnh 1-7. Kt cu t hp bn vi dm

    by

    yx

    b

    hx

    a

    Bn mtt/2

    t/2Z

    uw

    vw

    v uDm hng yDm hng x

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    Chng 1 - Khi nim chung v ca van... 31

    (1-12)

    (1-13)

    [ ]

    22

    1

    22

    0 0 0 0 0 0 0 0

    b a1 0 0 0

    2 21 1 1 1

    a 0 0 b2 4 2 4

    1 b 1 b 1a 0 a ab

    6 3 4 2 8B abt0 0 0 0

    1 10 b

    2 4a

    i xng 12

    a 1b

    2 6

    m m - m - m - m - m - m - m m + m + =

    - m - m

    - m +

    [ ]

    x x x x

    x x x x3 2 3 2

    x x x x2

    x dmx x

    x x3 2

    x

    A S A S0 0 0 0 0 0

    a a a a0 0 0 0 0 0 0 0 0

    12I 6I 12I 6I0 0 0 0

    a a a a0 0 0 0 0 0 0

    4I S 6I 2I0 0

    a a aaK EA S

    0 0 0a a

    0 0 0 0

    12I 6I0

    a ai xng 0 0

    4I

    a

    - - - - -

    - =

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    32 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    y y y y

    y y y y

    3 2 3 2

    y y y y

    2

    y dm

    y y

    y y

    3 2

    y

    0 0 0 0 0 0 0 0 0 0

    A S A S0 0 0 0 0

    b b b b12I 6I 12I 6I

    0 0 0b b b b

    4I S 6I 2I0 0 0

    b b bb0 0 0 0 0 0

    K E (1 14)0 0 0 0 0

    A S0 0

    b b12I 6I

    0b b

    i xng 0 0

    4I0

    b

    - - -

    - = - - -

    { }

    xi

    yi

    xi

    xi

    yi

    xj

    yj

    zj

    xj

    6

    xk

    yk

    zk

    xk

    yk

    xl

    yl

    zl

    xl

    yl

    F0F0

    F1M

    b 6Ma 6

    F0

    F0

    F 1

    M b 6

    a 6MR

    0F0F1

    Fb 6

    Ma 6

    M0

    F0

    F1

    F b 6M a 6M

    -

    = = -

    - -

    20

    0

    0

    8 10

    b 15

    a 18

    0

    0

    3 10

    b 15

    a 18abp ab (

    04 4

    0

    7 10

    b 10

    a 18

    0

    0

    7 10

    b 10

    a 18

    - g

    + -

    - -

    1 15)-

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    Chng 1 - Khi nim chung v ca van... 33

    Hnh 1-8. p lc nc trn bn mt ca van

    xt 2 h

    xt / 2

    A b ' dZ+

    = , xt / 2 h

    xt / 2

    S b ' ZdZ+

    = , xt / 2 h 2

    xt / 2

    I b ' Z dZ+

    = ln lt l din tch

    mt ct, mmen lc tnh v mmen qun tnh ca dm theo trc x, b l rng ca dm, ch cn khi tnh ton i x thnh y trong cng thc l tnh ton c.

    Nu cn phi xt ph ti ngoi, ch cn p lc nc P0 +gy tc dng ln bn mt ca van (xem hnh 1-8, trc y vi hng mt t, trc x v trc z song song vi hng mt t, trc z ch xung hng h lu).

    Sau khi dch chuyn v tr, lc tc dng u ln nt {R}e nh cng thc (1-15) biu th.

    (4) Khi c ma trn cng ca cc phn t v lc tc dng ca im nt, c th tp hp chng li, hnh thnh tng ma trn cng ca kt cu, ng thi theo iu kin cn bng ca lc trn im nt, to ra cc nhm chng trnh sau y:

    { }n

    ij ij 1

    K R=

    d = (i = 1, 2, 3,..., n); (1-16)

    Trong : m

    sij

    s 1K

    = - tng ma trn cng, nguyn t hng i, ct th j. sijK phn lng

    nguyn t do phn t S cung cp (tng s phn t l m); m

    si ij

    s 1R K

    == - tng ngoi lc tc dng ln im nt i do ph ti gy ra, siR l

    phn lng ngoi lc do phn t S cung cp;

    { }d - ma trn ct chuyn v ca im nt l s cha bit c xc nh trong nhm phng trnh (tng s l n).

    Trc khi gii phng trnh (1-18) cn phi cn c vo iu iu kin bin, tin hnh x l iu kin bin, tc l cn phi phng s vn ng th cng ca tng th kt cu.

    gby

    x

    zi

    j

    l

    k

    po

    b

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    34 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    V d: i vi bin ca gi c nh

    { }T u, v, , , 0x y

    w wd = w =

    i vi bin ca gi n gin w = 0 i vi gi bin ca hnh hc v ph ti i xng (1-17)

    i xng vi trc x, v 0y

    w= =

    i xng vi trc y, u 0x

    w= =

    (5) Chng trnh my tnh

    Tm li gii ca cng thc (1-18) trn my tnh in t, ng thi trong cng mt chng trnh tnh ton xong ton b ng sut trong cc phn t. V d, ng sut ca b mt di im gia trong phn t e ca bn l:

    { } [ ] { }x

    e1y S C

    -

    s s = s = d

    t

    (1-18)

    Trong :

    [ ]S xem cng thc (1-19); 1C- xem cng thc (1-11)

    { }ed l chuyn v ca im nt ca phn t e do my tnh xc nh c.

    [ ]

    ( ) ( ) ( ) ( )

    2

    2 2

    ES

    1

    b a0 1 0 0 0 0 0 0 t 0 t

    2 2b a

    0 0 0 0 1 0 0 0 t 0 t (1 19)2 2

    1 1 1 1 10 0 a 0 0 b 0 0 0 t 0

    2 4 2 4 2

    3at bt at 3 bt 3abt 3 abt

    2 2 2 2 4 43 at bt at 3bt 3 abt 3abt

    2 2 2 2 4 4

    1 at 1 bt 3 1 a t 3 1 b t0 0

    2 2 8 8

    = =- m

    m m - -m

    m m -m - - - m - m - m - m - m

    - - -m - m - - m

    - m -m - - - m -

    - - m - - m - - m - - m

    }

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    Chng 1 - Khi nim chung v ca van... 35

    ng sut ca bin cnh trn, di im gia ca phn t dm hng x v phn t dm hng y, nh cng thc:

    (1 20)

    (1 21)

    Trong :

    x xt

    H h2

    = + ; y yt

    H h2

    = + ;

    { } { }eex y,d d - chuyn v im nt ca phn t dm do my tnh in t xc nh.

    1.9.3. Mt s quy nh trong thit k kt cu ca van Khi thit k kt cu ca van thu cng nn c gng theo tnh hnh t hp ph ti

    bt li nht c th pht sinh trong thc t, tin hnh tnh ton cc mt: Cng , cng v tnh n nh v.v...

    tr s ng sut ln nht ca kt cu do tnh ton cng thu c khng vt qu 5% ng sut cho php ca vt liu.

    T s f/L ca vng ln nht ca cu kin chu un vi khu tnh ton ca n. T s L/r dn di tnh ton ca cu kin chu ko, chu nn vi bn knh quay v ca mt ct v kch thc mt ct nh nht ca cu kin chu ti trng, u phi tun th phm vi cho php ca quy phm.

    1.10. Mt s ca van nghin cu v ng dng

    Hin nay c hng chc loi ca van c p dng trong thc t, nhng trong s tay ny ch trnh by c mt s ca van thng c p dng ph bin nht, cn mt s ca van khc ch xin c gii thiu s nguyn l.

    1.10.1. Ca van phng L loi c ng dng rng ri, c kt cu n gin v vn hnh c tin cy

    cao, nhc im l lc ko nng v phi ko ton b trng lng ca v phi thng ma st do p lc nc gy ra... v chim khng gian pha trn p.

    { } { }trn

    e

    x xx x

    di x

    1 t 1 t0 0 0 0 0 0

    a 2a a 2aE

    H H1 10 0 0 0 0 0

    a a a a

    - - s s = = d

    - -s

    { } { }trn

    e

    y yy y

    di y

    1 t 1 t0 0 0 0 0 0

    b 2b b 2bE

    H H1 10 0 0 0 0 0

    b b b b

    - - s s = = d - s

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    36 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1.10.2. Ca van cung - Ca van cung trc ngang: L loi ca cng c ng dng ph bin bi u im

    ca ca cung lc ko nh v ch cn ko mt phn trng lng ca v p lc nc thng i qua tm quay nn khng trc tip cn tr lc ko m ch c tc dng gy ma st ci quay, vn hnh c tin cy cao. Nhc im l chim din tch trn cng trnh.

    - Ca van cung trc ng: Thng t dng v cng lm vic theo s cng xn, nn khng lm c khoang rng.

    1.10.3. Ca van Clape trc d i (ca sp) y l loi ca van c nhiu u im, lc ko nh, lc c phn u ln cc m

    nn c th lm ca rng, nhc im l trc quay nm trong nc.

    1.10.4. Ca van Clape trc trn Loi ca van ny thng dng tiu ng v ngn triu hoc ngn l t sng,

    nhc im ch ngn nc mt chiu v thng ng dng cho loi cng nh.

    1.10.5. Ca van hnh qut

    c b tr trn cc p trn, khi m ca nm vo trong thn p. u im c th lm khoang rng, c th h tr ng m bng thy lc. Nhc im ca van c kt cu phc tp hn so vi ca Clape nn ng dng cn t.

    1.10.6. Ca van mi nh L loi ca van c ng m bng thu lc, c th lm khoang rng, c ng

    dng cho nhng cng trnh iu tit l ln, nh p dng p y t nm 1937. Nhc im c tin cy khng cao.

    1.10.7. Ca van tr ln Hin nay t s dng.

    1.10.8. Cc kiu ca quay trc ng y l loi ca van mi c pht trin nc ta trong hai thp k va qua. - Ca van cnh ca t ng. - Ca van cnh ca khng t ng. - Ca bn lch.

    1.10.9. Cc kiu ca quay trc ngang y cng l loi ca mi c pht trin trong thp k va qua. - Bn quay trc gia, bn quay khong 1/3 t di ln. - Bn quay trc gia nhiu lp.

    1.10.10. Cc kiu ca van t ng thy lc iu tit trn knh Hin c nhiu loi ca van iu tit mc nc, iu tit lu lng c ng

    dng trn nhiu trn nhiu h thng thy nng trn Th gii.

    1.10.11. Cc kiu ca van u tu Hin c nhiu loi ca van c th ng dng cho u tu nh: Ca ch nhn, ca

    phng chm, ca phng ng, ca phng ko, ca clape, ca y ngang, ca cung ng, ca mt phn hnh trn.

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    Chng 1 - Khi nim chung v ca van... 37

    Chng 1 11

    Khi nim chung v Ca van trong cng trnh thy li 11

    1.1. Vai tr nhim v ca ca van 11

    1.2. Cu to ca van 11

    1.3. Phn loi ca van 11

    1.4. Chn loi ca van cho cng trnh 12

    1.4.1. Vng ven bin ng bng sng Cu Long 12

    1.4.2. Vng ven bin Trung B 13

    1.4.3. Vng ng bng Bc B 13

    1.4.4. Ca trn p trn h cha v p dng vng Trung du v min ni 13

    1.5. B tr ca van trong cng trnh 13

    1.5.1. i vi cng h 13

    1.5.2. i vi cng kn 14

    1.6. Lc v t hp lc tc dng ln ca van 14

    1.6.1. Lc tc dng 14

    1.6.2. T hp lc 14

    1.7.1. Thp 15

    1.7.2. Gang 18

    1.7.3. ng 18

    1.7.4. Cao su 18

    1.7.5. Vt liu tng hp Composite 19

    1.7.6. B tng ct thp 19

    1.8. Nhng vn cn l u trong thit k ca van 19

    1.9. Ph ng php tnh ton 21

    1.9.1. Phng php phn tch h kt cu phng 22

    1.9.2. Phng php phn tch h kt cu khng gian 28

    1.9.3. Mt s quy nh trong thit k kt cu ca van 35

    1.10. Mt s ca van nghin cu v ng dng 35

    1.10.1. Ca van phng 35

    1.10.2. Ca van cung 36

    1.10.3. Ca van Clape trc di (ca sp) 36

    1.10.4. Ca van Clape trc trn 36

    1.10.5. Ca van hnh qut 36

    1.10.6. Ca van mi nh 36

    1.10.7. Ca van tr ln 36

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    38 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1.10.8. Cc kiu ca quay trc ng 36

    1.10.9. Cc kiu ca quay trc ngang 36

    1.10.10. Cc kiu ca van t ng thy lc iu tit trn knh 36

    1.10.11. Cc kiu ca van u tu 36

  • Chng 2 - Thy lc ca van 37

    Chng 2

    Thy lc ca van

    Bin son: GS. TS. Trng nh D

    2.1. Khi nim chung

    Ca van l b phn chu lc tc ng ca dng chy nn c tnh cht thy lc quan trng:

    - Nng lc x nc tt, ngha l m khc nhau - h s lu lng tng i ln hoc c h s cn tng i nh.

    - Lc tc dng thy ng n nh r rng, lm cho lc ng m tng i nh v n nh, tnh nng ng m tng i tt, thao tc linh hot thun tin.

    - Phn b p lc nc u n v trng thi dng chy n nh, ti ca van v ti cng trnh thy cng ln cn, khng c hin tng kh thc.

    - p lc mch ng v cng chy ri ca dng chy tng i nh, khng gy chn ng c tnh nguy hi.

    2.2. Nng lc x n c

    Ca van mt ni chung thng p dng cho cc trn x l ca h cha v cng ng bng. Trng thi dng chy khi chy qua p trn v cng thng c hai loi: chy trn v chy l.

    Xc nh im phn gii ca chy trn v chy l l v cng quan trng, n c quan h vi cc nhn t: Hnh thc nh trn, hnh thc ca van, iu kin mc nc thng h lu v m tng i ca ca van v.v...

    i vi loi trn v loi ca van thng gp, iu kin phn on chy l nu trong bng 2-1.

    Bng 2-1. Cng thc phn on dng chy qua l

    Loi ngng trn Loi ca Cng thc phn on

    Trn nh rng Ca van phng hoc ca van cung e/H 0,65

    Ca van phng e/H 0,75

    Trn thc dng Ca van cung

    Khi q2/gH < 5 e/H 0,75 Khi q2/gH > 5 e/H 0,8

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  • 38 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Trong : e- cao m ca van (m);

    H- su nc thng lu t nh ngng tr ln (m);

    q- lu lng n v qua ngng (m2/s);

    g- gia tc trng lc (m/s2).

    Khi chy l, lu lng dng x qua ming l c tnh theo cng thc:

    1Q be 2gH= m ; (2-1)

    Trong : b- b rng ca l cng (m);

    e- m ca ca van (m);

    m1- h s lu lng chy l. Tr s ca n c quan h ti loi hnh ngng trn, loi hnh ca van v m tng i ca ca van, xem bng 2-2.

    Bng 2-2. H s lu lng chy l m1

    Loi ngng trn Loi ca Cng thc tnh ton tr s m1

    Ca van phng m1 = 0,6 0,18 n1

    Trn nh rng Ca van cung

    m1 = (0,97 0,26q)n1 Phm vi thng dng:

    0,44 < q < p/2 n1 < 0,56

    Trn thc dng Ca van phng Ca van cung

    m1 = 0,745 0,274n1

    m1 = 0,685 0,19n1

    Trong : n1- m tng i ca ca van, 1n e H= ;

    q - gc kp gia tip tuyn vi ng nm ngang ca vin y ca cung khi m l n1, tnh bng radian.

    i vi cng ng bng, nu di cng l dng chy ngp, h s lu lng m1 tra t bng 2-2 nhn thm vi h s chy ngp s.

    H s s tnh theo cng thc:

    ( )

    ( )cln 1 Z H

    0,95ln h" / H

    - Ds = ; (2-2)

    Trong :

    DZ- chnh mc nc thng h lu (m);

    h"c- su nc ti mt ct thu hp nht ca dng chy di ca van (m).

    Dng chy d i ca su Ca van su l loi ca van c lp t cc l tho nc di su.

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  • Chng 2 - Thy lc ca van 39

    Nng lc tho nc ca ca van t di su c quan h vi tng cc tn tht ma st theo dng chy v tn tht cc b. Nng lc tho nc ca bn thn ca van bng ct nc ti v tr trc ca van, thng bng chiu cao ng (ch nht) hoc bng ng knh ng trn tr i su co hp sau ca van lm ct nc cng tc hu hiu H. Tnh ton theo cng thc:

    2Q A 2gH= m ; (2-3)

    Trong :

    A- din tch ming l khi ca van m ht (m2).

    m2- h s lu lng theo nh ngha din tch A. Tc l khc vi m1 ca cng thc (2-1). Tr s ca n tnh theo cng thc:

    22

    1

    1m =

    + x; (2-4)

    x2- h s tn tht ca ca van. Tr s x2 ca cc loi ca van c th tra trong bng 2-3.

    Bng 2-3. H s tn tht tht ca ca cng x2

    Loi ca Trng thi dng chy h lu H s tn tht x2

    (a) 2

    2 22

    11,8 0,81n

    n

    x = -

    Dng chy c p

    (b) 2

    2 22

    1. n

    n

    x = h -

    (ch thch 2)

    (c) 2,23

    2 22

    10,78. 0,65.n

    n

    x = -

    Ca phng

    Chy t do

    Hnh thc vin y

    (d) 1,67

    2 22

    10,5. 0,65n

    n

    x = -

    Chy c p 2

    2 33

    10,3 1,3. n

    n

    x = + -

    Ca cung

    Chy t do x2 tra theo hnh 2-2

    Van a ( )2 1000exp 5,57x = - b

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  • 40 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Trong :

    n2 - m tng i ca van, tnh ton theo chiu cao l h, n2 = e/h;

    n3 - m tng i ca ca van hnh cung, tnh ton theo gc trung tm j, n3 = j/j0 hoc n3 n2 0,05;

    b - gc quay khi m ca van bm, tnh bng Radian, khi m ht b = p/2;

    h= 1+0,43j+0,41j2, j xem hnh 2-1, tnh bng Radian.

    Hnh dng y ca van phng, xem hnh 2-1.

    Hnh 2-1. Hnh dng vin y ca ca van phng

    0

    Dng chyDng chy Dng chy

    R=0,875 t

    0,9

    t

    t

    0,125 t

    ( a ) ( b ) ( c )

    30j

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  • Chng 2 - Thy lc ca van 41

    xH

    s

    lc

    cn

    1.00.90.80.70.60.50.40.30.20.10

    0. 01

    0.02

    0.03

    0.04

    0.05

    0.08

    0.1

    0.2

    0.3

    0.5

    0.06

    0.6

    0.8

    1

    2

    3

    4

    52

    1.81hh

    1.6

    1.41.2

    eh2n

    e

    h h1

    Hnh 2-2. Tr s h s lc cn ca ca van cung x2

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  • 42 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    2.3. p lc n c tc dng ln ca van p lc ca nc tc dng ln ca van l ti trng ch yu nht trong thit k ca

    van. p lc nc tnh tng i r rng ng tin tng. Tnh ton p lc ny c th xem cc ti liu thy lc. y ch tp trung gii thiu khi x nc qua ming l, dng chy mnh ca nc dn n p lc nc ng. p lc nc ng c th phn ra hai loi: p lc bnh qun theo thi gian v p lc mch ng. Vn tho lun di y l p lc bnh qun thi gian. Dng phng php tnh ton tng t nh p lc nc tnh.

    2.3.1. Ca van phng Do vic s dng ct nc trc ca van phng l lc bn ngoi tnh lc ng

    m ca van cho nn cng vic nghin cu p lc nc ng tc dng ln ca van cng c ch nhiu. Di y l phn bit trnh by p lc nc ng tc dng ln cc b phn: Mt bn thng lu, dm ngang nh ca v vin y ca.

    a) p lc nc ng tc dng ln bn mt thng lu

    Phn b p lc nc ng tc dng ln bn mt thng lu ca ca van phng xem hnh 2-3.

    Hnh 2-3. Phn b p lc thy ng ca bn mt thng lu

    Trong hnh 2-3a l ca van phng h, hnh 2-3b l chy ngp hai ca van x nc gin on.

    Theo phn tch l thuyt v kt qu th nghim, tng p lc nc ng nh hn tng p lc nc tnh nhng chnh lch khng ln. V vy, khi phn tch kt cu, tnh ton theo ct nc tnh l thch hp v thin an ton. Nu cn thit phi tnh theo p lc

    nc ng, th c th dng cng thc (2-5) tnh h s lc ng x (nh ngha l t s ca tng p lc nc ng nm ngang P v tng p lc nc tnh nm ngang PT) hoc gi l h s lc y nm ngang.

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  • Chng 2 - Thy lc ca van 43

    1

    T

    P 2 2K 1 3 2K 1 1tg

    1P 2 2 KK K1n

    - e + p +x = = - - - p

    ; (2-5)

    Trong : k - h s th nghim;

    n- m tng i ca ca van;

    e- h s co hp thng ng ca dng chy ra di ca van.

    tin cho vic tnh ton, a cng thc (2-5) v thnh ng cong x-n nh hnh 2-4.

    Hnh 2-4. ng quan h x v n

    b) p lc nc ng trn dm ngang ca nh ca van

    p lc nc ng tc dng ln dm ngang ca nh ca van, c hai trng hp ty theo v tr ca ca van phng.

    Ca cng b tr trn mt p, p lc nc ng ca nh ca c quan h vi hnh dng mt p. Ni chung, nu gia ca van v mt p c khe h rt nh th p lc

    1.0

    0.9

    0.8

    0.7

    0.6

    0.5

    0.4

    0.3

    0.2

    0.1

    0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

    H

    s l

    c

    y n

    m n

    gang

    x

    m tng i ca van n

    ng cong tnh ton

    Th nghim m hnh Tn An Giang

    Th nghim m hnh Tam Hip

    Th nghim m hnh Vn Phong

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  • 44 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    nc ng nh ca trn c bn bng p lc nc tnh. Cn nu trn mt p khng c tng lm, m gia ca van v mt p hnh thnh ng thng nc th p lc nc ng nh ca h xung, nhng nh hng khng ln, vn c th xem xt theo p lc nc tnh. S tn ti tng lm trn mt p, ch yu nh hng n s phn b p lc trn mt h lu ca van, lm cho lc ng m ca van c th c h thp.

    c) Ca van b tr trong ging, hnh (2-5b) v hnh (2-6)

    p lc nc ng ti nh ca thay i ty theo kch thc tng i ca ca van v ging t ca van.

    Cho h l su nc t ng mt nc trong ging ca ti y l, H0 l ct nc trc ging sau khi xt ti tn tht ct nc do qu trnh ng chy ca ng x nc.

    10

    20

    h 1

    bH1

    b

    =+ m

    ; (2-6)

    (b)(a) Hnh 2-5. B tr ca van trong cng

    Nu ly h s lu lng, m2 = 0,7 th cng thc (2-6) c th v thnh hnh 2-7. Trong hnh ny c a vo mt s ti liu thc o ca mt s cng trnh Trung Quc (Tng Nguyn, Thch Kh, Song Bi v.v...).

    Khi 0 1b / b 3> , tr h/H0 gn n nh, c ngha l khi c p lc nc ng nh

    ca tng i ln, nn chn tr s 0 1b / b tng i ln.

    0 2b 5b .

    1 2b b hoc b1 = 100 mm.

    ( ) 00,05 0,1 aD = m D khng nh hn 300 mm.

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  • Chng 2 - Thy lc ca van 45

    Hnh 2-6. Kch thc tng i ca ca van v ging cng

    d) p lc nc ng trn vin y ca van

    p lc nc ng tc dng ln vin y ca van c quan h rt ln ti hnh dng vin y v m ca van. Xt hnh thc vin y ca ca van nh hnh 2-6.

    Theo phn tch l thuyt, khi m ca van t n mt tr s no , gc

    nghing thng lu ca vin y a tn ti mt tr s cc hn ak.

    Nu ka < a th trn vin y xut hin lc ht xung. Cn nu kaa > th trn

    vin y xut hin lc y ln. Quan h gia chng nh hnh 2-8.

    Cho b l h s lc y ln, biu th t s lc y ln (tr s m l lc ht xung) v p lc thy tnh trn mt chiu vin y (H0 - a). a tr s b ca cc gc nghing vin y khc nhau thu c qua th nghim v thnh hnh 2-9 2-12.

    D

    e

    Ho

    h

    Dng chy

    ng dc

    ng mt nc ging ca

    b2

    aa

    'aao

    T D

    bbo b1

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  • 46 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Hnh 2-7.ng cong 0 0 1h / H b b-

    Hnh 2-8. Gc nghing tm thi ca vin y ca van phng

    1.0

    0.8

    0.6

    0.4

    0.2

    0 1 2 3 4 5

    hHo

    b1bo

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  • Chng 2 - Thy lc ca van 47

    Hnh 2-9. ng cong tr s b

    a = 50, 300, 450, v/T = 0, e/T = 0 (trong hnh a nn l a')

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  • 48 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    b

    4

    5

    6

    7

    8

    9

    10

    3

    2

    1

    02 4 6 8 10 12 14 16 18 20 22

    Ta

    Tao = 5.5

    6.0

    1.5

    22

    Hnh 2-10. ng cong tr s b (a' = 450, n = 0, e = 0)

    (Trong hnh a l a')

    Hnh 2-11. ng cong tr s b (a' = 52,50, n = 0, e = 0)

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  • Chng 2 - Thy lc ca van 49

    1

    Hnh 2-12. ng cong tr s b (a' = 600, n = 0, e = 0)

    Theo quy nh ca quy phm thit k ca van thp, khi tnh ton lc ng ca,

    nn xem xt theo trng thi ca van gn nh ng hon ton, tc ly b =1,0. Cn khi tnh ton lc chng , tr s b c xem xt theo cc m ca van khc nhau. T ng cong th nghim trn, c th ly tr s b mt cch n gin nh bng 2-4.

    Bng 2-4. Tr s h s lc y ln b

    a/T b

    a' 2 4 8 12 16

    600 0,8 0,7 0,5 0,4 0,25

    52,50 0,7 0,5 0,3 0,15 0,25

    450 0,6 0,4 0,1 0,05 0,25

    Bi v nhng tr s b lit k trong bng thch dng vi trng hp chy t do h lu ca van, tc yu cu:

    - i vi ca van ca ng x nc 0 < a

  • 50 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    2.3.2. Ca van cung

    p lc nc ng tc dng ln bn mt thng lu ca van cung tnh ton theo cng thc l thuyt th nng dng chy:

    ( )2

    1c 2cyD

    1 2

    K Kp H y H a

    K K

    = g - - -

    (2-7)

    Trong :

    1

    1

    2 2 2 2

    yK

    ysin tg

    a a y 2y R a

    -

    = + - + -

    ;

    2

    1

    2 2 2 2

    yK

    ysin tg

    a a y 2y R a

    -

    = - + - + -

    .

    K1, K2 tra hnh 2-15 tm c K1c, K2c l tr K1, K2 ti im c, cng c th dng

    y=a tra hnh 2-15 s c. Cc k hiu khc, xem hnh 2-14. p lc nc ng tnh ton theo cng thc (2-7) tng i ph hp vi kt qu th nghim m hnh.

    Vin y ca ca van cung phn ln khi ngn nc c dng hnh ao, dy rt nh, din tch tip xc vi nc ng khng ln, nh hng ti tnh ton lc ng m tng i nh, nn t c ch n. Nu cn thit phi tnh ton, cng c th tin hnh theo phng php tnh ton cnh ca cng phng, nhng lc ny phi ch quan

    h gc nghing a thng lu vin y thay i theo m trong qu trnh m cng.

    Hnh 2-14. p lc nc ng tc dng ln bn mt thng lu ca van cung

    H

    d a

    g.(H -

    a)

    y 2v

    gy

    2yDPg

    R

    c

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  • Chng 2 - Thy lc ca van 51

    R a

    48121620242832

    4.0

    3.8

    3.6

    16 14

    ay3.

    23.

    02.

    82.

    62.

    42.

    22.

    01.

    81.

    61.

    41.

    2

    12 10 8 6 4 2 03.

    4

    Hn

    h 2

    -15a

    .

    ng

    con

    g K

    1

    K1

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  • 52 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Hn

    h 4

    - 15.

    ng c

    ong

    K , K

    20 18

    3.4

    024681012

    1.2

    1.4

    1.6

    1.8

    2.0

    2.2

    2.4

    2.6

    2.8

    3.0

    3.2

    y a

    1416

    3.6

    3.8

    4.0

    32 28 24 20 16 12 8 4

    aR

    12

    Hn

    h 2

    -15b

    .

    ng

    con

    g K

    2

    K2

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  • Chng 2 - Thy lc ca van 53

    2.3.3. Ca van qut (hnh 2-16)

    T yu cu chy trn nh ca van m ni, ngoi hnh ca ca van qut nn thit k theo ng cong nh trn ca trn phi chn khng. Nhng xt v gc ch to n gin thng to thnh mt on cung trn gn vi ng cong .

    p lc nc ng tc dng ln bn mt thng lu cnh cng ca ca cng cnh li, bin i rt ln. Nu a t s gia tng p lc nc ng trn bn mt khi m

    q v tng p lc nc tnh (trong b tr chung ly q -600) khi ng ca van, nh ngha l h s lc ng x, th quan h gia n v gc m q nh hnh 2-16.

    ng thc trong hnh l ng cong l thuyt, im en l kt qu ca th nghim m hnh.

    T kt qu th nghim c th thy, khi q < -100, p lc nc ng rt khng n nh (khu gch cho trong hnh), xut hin p lc nc m, ca van d pht sinh chn ng.

    Hnh 2-16. H s lc ng ca ca van qut

    2.3.4. Ch thy lc khi trn qua ca sp Dng chy qua ca van sp c tnh nh p trn, c th tnh nh p trn nh

    rng, v cng c th tnh nh p trn thc dng ty thuc vo chiu cao p v chiu di ca van khi m ht.

    1.4

    1.2

    0.4

    0.6

    0.8

    1.0

    0.2

    0- 20 0 20 40 60 80- 40

    0 0 0 0 0 0 0

    x

    q

    + q - q

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  • 54 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    iu ng lu l p lc trn mt ca van sp khi dng chy trn qua l p lc

    nc ng v bin i theo gc m a ca ca. Khi a trong khong 60 75 th p lc trn mt ca l p lc thy ng nh hn p lc thy tnh, thng tnh gn ng p lc thy tnh hnh thang. Nhng thc t p lc ti mt ct trn mt ca l:

    2v

    P h2.g

    = - (2-8)

    Trong : h - su dng chy;

    v - lu tc ti mt ct tnh p lc.

    c tr s p lc chnh xc thng ngi ta phi tin hnh o trong m hnh th

    nghim. Trong thit k tnh lc ko ca coi p lc trn mt ca l p lc thy tnh, s thin an ton cho kh nng ko ca. Cn p lc mt di ca khi c dng chy qua ca b gim thp hn p lc kh tri, hoc c th chn khng v dng chy cun ht khng kh ra ngoi. V vy phi tnh ton v th nghim xc nh tit din ng thng kh vo di ca van cho vng ny c p lc kh tri. iu lm cho vic tnh lc ko ca c chnh xc v ca lm vic n nh.

    Hnh 2-17. Dng chy qua ca van sp

    Biu p lc dng chy

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  • Chng 2 - Thy lc ca van 55

    Chng 2 37

    Thy lc ca van 37

    2.1. Khi nim chung 37

    2.2. Nng lc x n c 37

    2.3. p lc n c tc dng ln ca van 42

    2.3.1. Ca van phng 42

    2.3.2. Ca van cung 50

    2.3.3. Ca van qut 53

    2.3.4. Ch thy lc khi trn qua ca sp 53

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  • Chng 3 - ca van phng 55

    Chng 3

    ca van phng

    Bin son: GS. TS. Trng nh D

    3.1. Ca van phng

    Ca van phng l hnh thc ca ra i sm nht trong cc loi ca van s dng trong cng trnh Thy li v n nay cn p dng rng ri do ca van phng c kt cu n gin, d gia cng ch to, vn hnh thun li. Ca phng c s dng nhiu trong cc cng trnh ly nc, tiu nc, trn p trn cn iu tit lu lng, trn cc cng trnh iu tit trn knh. Ca p dng c chiu rng t 0,6 m n 80 m, thng dng nh hn 20m. Ca c th l bng g, vt liu tng hp, b tng ct thp v thp. Hin nay phn ln lm bng thp.

    3.1.1. u nh c im ca ca van phng

    a) u im

    - C th lm ca vi kch thc ln

    - Kch thc khng gian n chim theo hng dng chy tng i nh

    - Tm ca c th di di khi ming l, tin cho vic kim tra duy tu.

    - D s dng my ng m kiu di ng.

    b) Nhc im

    - Yu cu t my tng i cao v tr pin cng tng i dy

    - Rnh ca c nh hng ti dng chy, i vi ca cng c ct nc cao c bit bt li, d xy ra hin tng kh thc.

    - S lng cu kin chn vo b tng tng i nhiu.

    - Lc ng m tng i ln, chu nh hng nhiu ca lc ma st, do cn phi dng thit b ng m c cng sut ln.

    - Khi ko ln ca van treo trn cao, chu tc dng ca gi bo.

    3.1.2. Cc b phn chnh ca ca van phng - Bn mt thng lm bng thp c chiu dy khng nh hn 4mm i vi ca c

    chiu rng b hn hoc bng 2m v ct nc b hn 2m; chiu dy khng nh hn 6mm i vi ca c chiu rng v chiu cao ct nc ln hn 2m. Vng chua mn

    chiu dy bn mt ln hn 8 10 mm, c th dy hn n 14mm.

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  • 56 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    - Dm chnh ngang dng c i vi B 6m v kiu gin vi B > 6m. - Dm bin.

    - Tm trt gn vo dm bin hoc bnh xe ln.

    - Tai ko.

    - Bnh xe c hoc c trt.

    - Giong chn nc.

    3.1.3. Cu to ca cc b phn chnh

    a) Dm chnh

    Kt cu dm chnh thng b tr theo hng ngang 2 u ta ln dm bin (ngm n hi). Vi ca nh dm chnh nhn p lc trc tip t bn mt v dm ph ng truyn vo, dm ph ngang khng c.

    Dm chnh kt cu theo hai dng: Dm c v dm kiu gin. Thng thng kt cu gin theo hnh (3-1a) chu p lc nc 1 chiu v theo hnh (3-1b) chu p lc nc

    2 chiu. a = 45o

    h 1 1( )

    L 6 8

    Hnh 3-1

    a

    Hnh 3-2

    Trong thit k dm chnh c b tr v s lng v v tr th no chng nhn

    p lc u nhau hoc gn u nhau. Kt cu dm c, s lng dm 3. Kt cu kiu gin s dm chnh thng l 3.

    Ch : Kt cu dm c cn khot l thot nc khi nng ca ln nc khng ng li trong cc bng dm.

    b) Dm ngang y

    c cu to m bo lin kt vi chn nc y thun tin. V tr dm y cn

    tun theo theo iu kin l gc a > 30o (hnh 3-2). Tun th iu kin ny trnh c hin tng dng xoy di bng dm gim rung ng v lc ng m. Nu v kt cu

    b buc a < 30o th bng dm cn khot l m bo t l:

    F l rng20% (F - din tch)

    F bng dm .

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  • Chng 3 - ca van phng 57

    Hnh 3-3. S cu to ca van phng

    1- bn chn; 2- dm ngang nh; 3- dm ngang y; 4- dm chnh ngang; 5- dm ph ngang; 6- h dm ng; 7- thanh ging cho; 8- cc b phn ta ph; 9- m kn nc; 10- b phn treo; 11- trc ta hai bn; 12- b phn ta gi ng.

    c) Cc dm ph dc v ngang

    Sau bn mt l cc dm ph dc v ngang; kt cu dm ph c dng c thng

    chn thp ch I, T. Khi thit k cn b tr cc dm ph dc v ngang sao cho a

    nb

    = ca

    bn mt nm trong t l 1 < n < 2. y a l khong cch gia cc dm ph dc, b l khong cch cc dm ph ngang.

    d) Dm bin

    Dm bin nhn p lc t dm chnh, dm ngang y v nh cng vi mt phn t bn mt truyn vo. Kt cu dm bin thng c hai dng: Dng c ch C, I v dng hp.

    Kiu dm c thng dng cho ca trt, ca bnh xe ln c trc kiu cng xn. Kiu dm hp b tr cho ca c bnh xe nm ngay trong hp, trc bnh xe ngn kt cu chc chn.

    1

    5

    4

    6

    5

    7

    11

    1289

    102 6

    3

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  • 58 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Hnh 3-4. Ca van phng n

    Hnh 3-5. Ca van phng 2 lp

    e) Tai ko

    Tai ko ca ca l b phn ni ca vi u di cng ca thanh ko hoc mc ko ca c cu nng. Khi ca c chiu rng b hn chiu cao nn b tr mt im ko gia ca (1 tai ko). Khi ca c chiu rng ln hn chiu cao 1,5 ln nn b tr hai im ko v pha hai dm bin. Nhng ca c sc nng ln, trc tai ko c khi lng ln (> 50 kg) cnh ch tai ca nn b tr gi trc thun tin khi lp rp v tho d.

    Trong thc t ngoi b phn tai ko cn c b phn treo ca s dng vo vic treo ca trong thi gian sa cha cng trnh, bn thn ca hoc c cu my.

    g) B phn c

    C c tc dng loi tr kh nng mt u ca (dm bin hoc u trc bnh xe,...) chm vo b tng khe ca do ca b nghing lch.

    C cu to theo hai hnh thc: bnh xe v trt. Trong mt ca van hon chnh thng b tr 4 c bn v 4 c theo hng ngc dng chy.

    C bn c th b tr pha tn bng hoc pha i din vi tn bng nu khng c

    tng ngc. mt s trng hp c bn cn b tr trong lng dm bin. C ngc theo hng dng chy b tr ngay trn dm bin phn nm trong khe. Tc dng ca loi c ny l gim rung ng ca khi nng h tng phn.

    1622

    1400

    2600

    300

    150

    300

    100

    80

    1412

    1360

    1250

    1250

    650

    3.13

    12.8

    7

    6.2

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  • Chng 3 - ca van phng 59

    3.1.4. Ti trng v lc tc dng ln ca van phng

    a) p lc nc tnh

    Biu p lc Cng thc xc nh

    p lc nc P Cng thc xc nh v tr t p lc (Hc)

    2t

    1. .H .L

    2g t

    2.H

    3

    2 2t h

    1. .(H H ).L

    2g -

    2h

    tt h

    H1.(2.H )

    3 H H-

    +

    Trong : Ht - chiu cao ct nc thng lu;

    Hh - chiu cao ct nc h lu;

    Hc - khong cch t tng p lc P tnh t mt nc;

    L - chiu rng khoang cng.

    b) p lc nc ng (thnh phn nm ngang)

    Xut hin khi m ca tng phn; tr s p lc ng b hn p lc thy tnh (do tn tht ct nc khi chy qua ca).

    Trong tnh ton cn nh: Khi ca ng tr s p lc ng ca nc khng c, ngc li khi m tng phn tr s p lc thy tnh s khng c.

    Khi tnh s b tr s p lc ng ly bng tr s p lc tnh v tr tng ng.

    c) p lc bn ct lng

    2 2 0bc bc bcP 0,5. .h .tg (45 ).L2

    j= g - ; (3-1)

    Trong : hbc - chiu cao lp bn ct;

    j - gc nghing t nhin ca bn ct trong nc;

    gbc - trng lng ring ca bn ct trong nc; L - chiu rng bn ct tc dng ln ca.

    d) Lc ht y ca

    d aP P .b.L= , (kg); (3-2)

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  • 60 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Trong : Pa = 0,6 kg/cm2;

    b - chiu rng phn y ca tip xc vi ngng;

    L - chiu di.

    e) Trng lng bn thn ca ca (G)

    S b c th xc nh trng lng phn ng ca theo biu hnh 3-6.

    TC400

    300

    200

    10080

    605040

    30

    20

    108

    654

    3

    2

    1

    10 20 30 40 50 60 80 100

    200

    300

    400

    500

    600

    800

    1000

    2000

    3000

    4000

    5000

    6000

    8000

    1000

    0

    2000

    0

    3000

    0

    4000

    050

    000

    6000

    0

    8000

    010

    0000

    Q . L07

    G = f ( Q . L )07

    12

    3

    4

    Hnh 3-6. Biu s b tnh trng lng ca G

    1- ng vi ca bnh xe mt; 2- ng vi ca trt mt; 3- ng vi ca bnh xe su; 4- ng vi ca trt su.

    + Hoc c th xc nh theo cng thc A.R. Beredinski:

    G 0,055.F. F= (3-3)

    + Hoc c th theo cng thc P.A. Ephimp:

    4G 0,157.F. F= (3-4)

    Trong :

    F - din tch ca van.

    g) Ti trng do gi (tnh phn ca nm trn mt nc)

    gi giP F.q= , (kg); (3-5)

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  • Chng 3 - ca van phng 61

    Tm trt

    Trong :

    F - din tch b mt chu tc dng gi ca ca, (m2);

    qgi - cng p lc gi khu vc t cng trnh, (qgi = 25 100 kG/m2,

    thng tnh ton ly qgi = 45 kG/m2).

    3.1.5. Cc kiu ca van phng

    a) Ca phng trt

    (1) c im:

    + Ca van phng loi ny c tm trt c nh vo dm bin. Tm trt nhn ton b p lc ngang ca nc tc dng ln ca truyn vo khe ca; v vy khi nng h cn khc phc lc ma st trt.

    Cu to tm trt c th l mt tm lin tc hoc nhiu on tm c nh trn dm bin. gim nh ma st ln ngi ta c th lm c cu nhp trt (mt trt cong).

    + Vt liu tm trt: i vi ca nh thng l ng pA 9-4 hoc thp khng g 2X13, 1X18H9T; nhiu trng hp dng thp thng bn ngoi bc mt lp m khng g. i vi ca chu p lc nc ln dng g p k hiu C-

    chu ti trng phn b t 5003000 kG/cm2.

    + Tr s h s ma st trt ca tm trt v giong chn nc cho bng 3-1.

    Hnh 3-7. S b tr tm trt

    (2) Tnh lc nng h:

    - Lc nng:

    1 2 dT K .G K .W.f P= + + ; (3-6)

    Trong :

    K1 = 1,1; K2 = 1,2;

    W - tng p lc nc tc dng vo ca;

    f - tr s h s ma st trt;

    Pd - lc ht, xem cng thc (3-2);

    G - trng lng bn thn ca ca.

    - Lc h:

    'T 0,9.G 1,2.W.f= - (3-7)

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  • 62 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Nu T > 0 ca t h.

    T < 0 ca khng t h xung c phi n xung bng c cu my.

    (3) Phm vi s dng:

    Ca trt l hnh thc ca n gin nht trong cc loi ca. Kt cu gn, khe ca nh c li khi b tr cng trnh v vy ca trt c p dng nhiu cc cng trnh trn knh.

    Bng 3-1. H s ma st f

    Tr s f Loi Vt liu ma st v iu kin cng tc

    Ln nht B nht

    1. Thp vi thp (trng thi kh ro) 0,5~0,6 0,15

    2. Thp vi gang c (trng thi kh ro) 0,35 0,16

    3. G vi thp (trong nc trong) 0,65 0,3

    4. G p lp dnh keo i vi thp khng g (trong nc trong)(1)

    Theo cng nn dc: q>2000 kG/cm 0,1~0,11 0,05

    - q=2500~2000 kG/cm 0,11~0,12

    Ma st trt

    - q=2000~1500 kG/cm 0,12~0,13

    1. Thp vi ng en (trng thi kh ro) 0,3 0,16

    2. Thp vi ng en (c bi trn) 0,25 0,12

    3. Thp vi g p lp keo (c bi trn) 0,16~0,20 0,08

    Ma st trc trt

    4. Thp khng g i vi g p lp keo (c bi trn) 0,12~0,16 0,05

    1. Cao su vi thp 0,65 0,3 Ma st ngn nc

    2. Cao su vi thp khng g 0,5 0,2

    1.Thp vi thp 0,1 Ma st ln

    2. Thp vi gang c 0,1

    Ghi ch: (1) trn nhn b mt cng tc ca cu kin th nghim: Tm trt 6, ng trt 7.

    b) Ca phng bnh xe

    (1) c im:

    + Khc vi ca trt ch bnh xe nhn ton b p lc ca ca v truyn ln khe. Khi thit k thng chn s lng bnh xe trong mt ca l 4 v b tr mi bnh xe chu lc u nhau. Kt cu ca bnh xe c phc tp hn ca trt nhng vn c s dng rng ri v lc nng h nh (h s ma st ln nh hn h s ma st trt).

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  • Chng 3 - ca van phng 63

    a) b) Hnh 3-8. S ha bnh xe ca van

    + Cm bnh xe v trc c nh vo ca theo 2 dng nm trong hp ca dm bin v kiu cng xn. Khi b tr bnh xe nm trong hp, trc bnh xe s nh hn so vi kiu b tr cng xn.

    + Vt liu ch to:

    - Vi p lc ln bnh xe nh P < 5T dng gang xm c18.36 c21-40, GOCT1412-70.

    - Vi P > 5T dng thp 25; 45.

    + Trc dng thp 35, 45 GOCT 1050-60, hoc thp khng g.

    + trc c 2 dng: Bc ng, g p hoc bi. + H s ma st ln ca bnh xe v con ln ca ca c tnh n s lm vic trong nc:

    f1 = 0,1.

    (2) Tnh lc nng h:

    + Lc nng:

    - Vi bnh xe trc bng bc

    1 2 x y aT K .G K .(T T ) P= + + + (3-8)

    x 1 2W

    T .(f f .r)R

    = + (3-9)

    - Vi bnh xe trc bng bi

    1 2 x y aT K .G K .(T T ) P= + + +

    1x 11

    RWT .f .( 1)

    R r= + (3-10)

    Trong : Tx - lc sinh ra do ma st cm bnh xe vi ng ln;

    Ty - lc sinh ra do ma st ca vt chn nc vi ng trt;

    y cpT 2.H .b.a.f= (3-11)

    R - bn knh bnh xe (cm);

    r - bn knh trc (cm);

    f1 - h s ma st ln, f1 = 0,1;

    r1 - bn knh ca vin bi (cm);

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  • 64 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    R1 - bn knh vng ngoi ca ln (cm);

    f2 - h s ma st trt gia trc v bc (xem bng 3-1);

    f - h s ma st trt gia giong v ng trt (xem bng 3-1);

    b - chiu di ca giong chn nc chu tc dng ca ct nc H (cm);

    Hcp - ct nc trung bnh tc dng vo giong (cm);

    a - chiu rng mt giong p vo ng trt;

    K1 = 1,1; K2 = 1,2.

    Hnh 3-9. S tnh R1, R Hnh 3-10. S b tr khp iu chnh

    Cc k hiu xem cng thc (3-2) v (3-4).

    + Lc h:

    ' x yT 0,9.G 1,2.(T T )= - + ; (3-12)

    (Tx tnh theo iu kin cng thc 3-9 v 3-10)

    Nu T > 0 ca t h;

    T < 0 ca khng t h c.

    c) Ca kiu Wagon (hnh 3-10)

    i vi ca rng, u nc ln gim nh ng knh bnh xe, khi thit k thng p dng kiu Wagon.

    u im ca loi ca ny l tuy s bnh xe nhiu (8, 12...) nhng tip xc nh bnh xe vi ng ln u hn do b phn khp t iu chnh v lc tc dng ln mi bnh xe c th b tr u nhau.

    Nhc im chnh ca loi ca ny l khe ca rng v su i hi tr pin dy. Lc nng h tnh nh ca bnh xe.

    d) Ca 2 lp

    Gi ca 2 lp v n c hai lp t so le nhau cng chn mt khoang thot nc. Mi lp ca c th l ca trt hoc ca bnh xe hon chnh (hnh 3-5).

    Ca loi ny thng s dng u thuyn hoc khng th s dng 1 lp ca v ca c chiu cao qu ln, lc ng m b hn ch i hi phi lm 2 lp. Trong iu kin dng ca 2 lp s h thp cu cng tc, gim c lc ng m (trong nc ta in hnh loi ca ny l ca van cng cu xe).

    www.vncold.vn

  • Chng 3 - ca van phng 65

    Khi thit k ca 2 lp cn ch : i vi lp di phi c bnh xe c nm trn ng hng (thuc khe ca) chy sut t ngng ca ln nh tr pin.

    Chn nc gia 2 ca theo hng ngang (ch tip gip ca nh ca di v y ca trn) thc hin theo dng hnh 3-11.

    Ca trn

    Ca di 150 - 180

    100

    60

    y khe ca lp trn

    Thnh khe ca lp di

    Hnh 3-11. Kn nc gia hai lp ca

    3.1.6. Kt cu phn p ng ng khe van v giong kn n c

    a) Kt cu phn p

    Cng vi ca (phn ng), y l phn tnh nm di nc kh sa cha. V vy cc b mt tip xc vi nc v khng kh, c sn, m khng g cn thn. B mt ca ng trt cho bnh xe ln thng s dng thp khng g hoc m mt lp thp khng g bn ngoi.

    Hnh 3-12. B tr thp khe ca

    a), b), c) Cc kt cu thp trong rnh phai; d), e), f) Cc kt cu thp chn gn trong b tng.

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  • 66 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    1040-60 605

    10

    a)b) c)

    12 5

    5

    10

    40-60 60

    e)

    512

    d) f)

    Khe ca v cc chi tit thp p khc cn thi cng chnh xc, nu khng s nh hng ln n iu kin vn hnh qun l cng trnh, c nhiu trng hp phi c i lm li. Kt cu phn p thng gp xem hnh 3-12.

    b) Kt cu chn nc

    B tr giong chn nc xem hnh 3-13.

    Cc hnh t a) d) l chn nc bn ca ca phng trt;

    e) f) l chn nc bn ca ca c bnh xe.

    Chn nc y xem hnh 3-18a, b.

    Hnh 3-13. Cc kiu kt cu chn nc

    c) Kt cu chn nc khng c tng ngc

    i vi ca phng vt chn nc ngc vi dng chy (khng c tng ngc) th cn phi c bin php p cng bc bng nm thp, hoc cc bin php k thut khc nh b tr bnh xe lch tm v khe van c cn vt ti v tr ng ht ca ca (thng thng bnh nm vt, d ch to, d lp t v kn nc tuyt i), xem hnh 3-14.

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  • Chng 3 - ca van phng 67

    Hnh 3-14. Kiu kt cu chn nc cng bc

    3.2. Ca van cung

    Cng nh ca phng, ca cung c s dng rng ri trong cc cng trnh thy li c bit l trn trn, p dng v cng vng nh hng thy triu, nht l nhng ni c ct nc cao th u im ca n cng ni bt.

    3.2.1. u nh c im ca ca van cung

    a) u im

    (1) C th bt kn khoang cng c din tch tng i ln.

    (2) cao ca gi my v dy ca tr pin cng tng i nh.

    (3) Rnh ca khng nh hng ti trng thi dng chy.

    (4) Lc ng m tng i nh nh nh hng ca lc cn ma st i vi lc ng m kh nh v m men sinh ra do p lc nc tc dng vo ca i vi tm quay khng ln.

    (5) S lng cu kin tng i t.

    b) Nhc im

    (1) Tr pin cng i hi di.

    (2) V tr khng gian cnh cng chim tng i ln.

    (3) Khng th a ra ngoi khoang cng kim tra sa cha.

    3.2.2. Nhng kt cu chnh Ca cung c cu to 2 phn: Phn ng v phn tnh.

    a) Kt cu phn ng

    (1) Bn mt

    Bn mt dng hnh cung c tm thng trng vi tm quay ca ca. Bn mt nhn ton b p lc nc v truyn vo cc dm ph sau n. Chiu dy bn mt nht thit phi ln hn 6 mm.

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  • 68 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    a) b) c) d)

    Hnh 3-15. Ca van cung

    1- bn mt; 2- cc dm ph; 3- dm ng; 4- dm chnh; 5- cng van; 6- tn gia cng cng; 7- ci bn l.

    (2) Khung ng

    Khung ng c hnh thnh bi dm ph cong ng sau tn bng vi cc thanh ging ni dm chnh v thanh ng ca gin pha sau.

    (3) Dm pha sau

    Dm pha sau c hnh dng gin cng vi dm chnh to cho ca c kt cu khng gian chu xon tt. Dm ng hp thnh do b phn ca dm chnh, khung ng v cc thanh xin.

    (4) Cng

    Hnh 3-16. Cc dng kt cu cng ca van

    Cng l b phn nhn p lc t dm chnh truyn vo ci quay (trc quay) ca.

    Kt cu cng c dng phng (hnh 3-16b) v dng khng gian (hnh 3-16a). B tr cng c th thng gc vi dm chnh (thng s dng khi B 10 m), hoc b tr xin gc vi dm chnh (thng s dng khi B 10 m).

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  • Chng 3 - ca van phng 69

    (5) Dm chnh

    Ca cung trn mt thng cu to 2 dm chnh chu lc u nhau. Kt cu dm chnh c dng c v dng gin.

    Dng c thng l thp ch I, T hoc thp tm ghp thnh, kt cu ny thch hp

    vi ca c B < 8m v DH < 5m. Dng gin thch hp vi ca c B 8m v DH 5m. Xem hnh 3-16.

    b) Kt cu phn tnh

    1450

    14.3649

    4050

    10

    00

    250

    Hnh 3-17. Kt cu ci bn l ca van cung

    (1) ci quay:

    Ch to bi thp c 25, 45 GOCT hoc thp hn.

    (2) Trc quay:

    c c nh vo ci quay; ch to bng thp CT5, thp 35 hoc thp 45.

    Trc v ci nhn ton b p lc nc v trng lng bn thn ca truyn vo tr pin. ci ca van c c nh vo tr pin nh cc bu lng. Khi thit k cn ch vic b tr cc bu lng ny sao cho d thay th khi sa cha.

    (3) Giong chn n c

    Ca cung c chn nc y v 2 bn, vt liu giong thng bng cao su v n hi ln d kn nc.

    Kt cu kn nc c dng hnh 3-18.

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  • 70 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    110

    10 14 10

    a) b)

    c) d)

    20 5 20

    5

    Hnh 3-18. S b tr kn nc ca van a), b) Kn nc y; c), d) Kn nc bn.

    3.2.3. Xc nh v tr ca dm chnh

    A

    O

    B D

    C

    1

    2

    3

    4 P

    P

    5

    6

    7

    8

    b

    P 8

    7

    6

    5

    3

    1

    2 P a

    d

    1 P

    P 2

    c

    2 1

    4

    H

    Hnh 3-19. S xc nh v tr ca dm chnh

    Chia bn mt ra n on ty gn u nhau, trn mi on tm phng v ln ca hp lc trong on . t ni tip cc vect lc t s 1 n n (gi nguyn phng v theo cng t l).

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  • Chng 3 - ca van phng 71

    Ni im u ca vect th nht n im cui ca vect th n ta c c phng

    v ln ca tng hp lc ON . T A n im gia caON k ng thng gc gp

    ng cong ti B. BN v BO l phng b tr dm chnh v gi tr ca lc phn b u trn dm chnh (hnh 3-19).

    3.2.4. Cc kiu ca van cung

    a) Ca van cung thng (hnh 3-20a, b)

    b) Ca van cung c li trn trn (hnh 3-20c)

    Ngoi ca cung thng dng ta thng gp cn c ca cung c li trn bn trn. y l hnh thc ca kt hp gia ca cung v ca sp. Khi mun tho lu lng nh, h ca sp (bn trn ca cung), nc trn qua ca cung. Khi mun x lu lng ln, ko c ca cung ln. Hnh thc ca ny thng s dng cng trnh trn c lu lng x l thay i ln.

    c) Ca cung hai lp

    (1) Ca cung hai lp ng tm v cng ng knh (hnh 3-20d)

    Hnh 3-20. S ca cung 2 lp ng tm v cng ng knh

    (2) Ca cung hai lp ng tm bn knh khc nhau (hnh 3-21)

    Ca cung 2 lp t chng ln nhau v quay cng tm quay. Trc quay c hai bc, bc c ng knh ln dnh cho lp di, bc c ng knh nh dnh cho lp trn. Loi ca cung 2 lp c li ch khi cn tho lu lng nh th m lp trn, vn gi nc trong h cao hn ngng ca; khi x l ln m c hai lp.

    b)

    c)d)

    a)

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  • 72 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    6.35

    4.50G1

    T

    2G

    l = 8500

    a

    a

    5.10

    1

    2

    Hnh 3-21. S ca van cung 2 lp ng tm khc bn knh

    d) Ca cung phao (hnh 3-22)

    Tc dng ca phao l gim nh lc nng h. Loi ca ny thch hp khi cng trnh c tng ngc v c th thit k thm c cu i trng ng m t ng hoc bn t ng nh cng La Kh Vn nh (H Ty).

    i trng

    Phao

    Hnh 3-22. S ca cung phao

    e) V tr t tm quay ca cung

    Tm quay ca cung thng t trn tr pin, v tr t c khong cch ti ngng ca thng xc nh theo hnh 3-23.

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  • Chng 3 - ca van phng 73

    a)

    R

    H

    > 0,

    5m

    (0,6

    7 - 1

    ,10)

    .H

    b)

    R

    ng mt nc

    H

    (0,5

    0 - 0

    ,75)

    .H

    Hnh 3-23. S xc nh v tr tm quay ca van

    a) Ca van trong khoang cng; b) Ca van trong khoang trn.

    3.2.5. Xc nh p lc n c tnh tc dng ln ca van cung

    p lc nc tnh tc dng ln ca cung trn mt c trnh by trong bng 3-2. Tng p lc nc P

    2 2ng dP P P= + ; (3-25)

    a - gc to thnh gia P vi mt ngang

    d

    ng

    Parctg

    Pa = ; (3-26)

    Trong :

    L - chiu rng tnh ton ca ca;

    tngP - thnh phn p lc theo hng ngang pha thng lu;

    hngP - thnh phn p lc theo hng ngang pha h lu;

    tdP - thnh phn p lc theo hng ng pha thng lu;

    hdP - thnh phn p lc theo hng ng pha h lu.

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  • 74 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Bng 3-2. p lc nc tnh tc dng ln ca cung trn mt Chim 2 trang Bng ngang

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  • Chng 3 - ca van phng 75

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  • 76 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    3.2.6. Tnh trng l ng bn thn ca cung Trng lng ca van cung phn chuyn ng c th xc nh gn ng theo biu

    hnh 3-6, cc cng thc (3-3), (3-4) v thm cc cng thc sau:

    2 0,8nG A.(h. .H )= ;

    Trong :

    h - chiu cao ca van;

    Hn - ct nc di tm ca van;

    - nhp ca ca van;

    A - h s ng dng,

    i vi ca van nh ly 0,09; i vi ca van ln ly 0,052.

    Trng lng ca van cung c kt hp ca van Clape trn nh th trng lng l:

    Gcl = 1,25.G

    Trng lng ca phn tnh c th ly gn ng:

    Gt = 0,15.G

    3.2.7. Tnh lc nng h

    a) Lc nng

    '

    1 2 x y dn .G.g n .(T .r T .R) P .RT

    + + +=

    r; (3-27)

    Trong : n1 = 1,1; n2 = 1,2;

    G - trng lng bn thn ca van;

    g - tay n ca G i vi tm quay;

    x 2T P.f= ;

    P - tng p lc nc tc dng vo ci;

    r - bn knh trc quay;

    f - h s ma st gia tr v bc;

    y cpT 2.H .b.a.f= ;

    R - bn knh mp ngoi bn mt n tm quay;

    r - tay n ca lc ko n tm quay;

    Pd - xem cng thc (3-2);

    R - tay n lc Pd i vi tm quay.

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  • Chng 3 - ca van phng 77

    b) Lc h

    '

    x y d' 0,09.G.g 1,2(T .r T .R) P .RT- + +

    =r

    (3-28)

    Nu T > 0 th ca t h.

    c) Lc gi

    '

    x y d1,1.G.g (T .r T .R) P .RT

    - + +=

    r (3-29)

    Khi tnh ton s b lc nng h ca cnh tay n ca trng lng ly bng 0,8R v im t ca G nm trn phng ca P.

    3.3. Ca sp (ca Clape trc di) 3.3.1. c tnh c bn

    Ca sp hay cn gi l ca Clape trc di l ca c trc pha di gn vi bn cng trnh, c th lm khoang rng nh c nhiu gi ta trung gian y, kt cu n gin, gn, khng chim khng gian trn cng, khi m ca nm trong dng chy khng b nh hng gi bo, c kh nng iu chnh chnh xc mc nc v cho php x vt ni, kh nng lm vic nhanh nhy. Nhc im l ca nm trong nc kh sa cha.

    3.3.2. Ca sp iu khin bng c kh

    a) Cu to cc kiu ca

    (1) Kiu bn sp:

    Ca c cu to gm mt dm chnh ngang (1) nm phn u v cui hai u dm b tr im ko v neo ca, cc dm ng (2), u trn ni vi dm chnh v u di ni vi ci bn l (3), cc dm ph lin kt cc dm ng (4). ng tm ca

    cc ci quay ch cho php sai s 1,5 mm trn sut c chiu di ca. Hin nay d dng thi cng th cc ci quay c ch to sn trong nh my trn mt dm. y l kiu ca c ng dng ngy cng nhiu nh tnh u vit ca n nht l khi s dng xilanh thy lc ng m. M hnh kt cu loi ca bn sp ny c ng dng cng trnh ngn mn gi ngt Tho Long Hu chiu rng 31,5 m (hnh 3-24) v cng Duy Thnh (Qung Nam) chiu rng 20 m. www.vncold.vn

  • 78 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Hnh 3-24. Kiu bn sp gn trn dm y ca p Tho Long (Tha Thin Hu)

    1- dm chnh ngang; 2- dm ng; 3- cm ci quay; 4- dm ph ngang.

    (2) Kiu qu trm (hnh 3-25): Kiu dm rng

    Hnh 3-25. Ca sp kiu qu trm

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  • Chng 3 - ca van phng 79

    Loi ny c ng dng trn p trn, bn thn l mt dm rng, kt cu cng, chu xon tt, hin ti t c s dng.

    b) Xc nh lc nng ca

    1,1.G.g P.a 1,2.R.f.r

    Tt

    + + ; (3-30)

    Trong :

    g, a, r, t - cnh tay n ca cc lc: G, P, R v T i vi tm quay;

    G - trng lng bn thn ca;

    P - tng p lc nc tc dng ln ca;

    R - phn lc ti gi;

    r - bn knh trc quay;

    f - h s ma st trt.

    c) Phm vi ng dng

    Kiu ca bn sp c kt cu n gin, c ng dng cc p thp c ct nc

    4 7 m, thch hp cc p vng trung du, cc cng tiu ng bng cn lm khoang rng v cn ng m nhanh thot l. Hin nay p dng xilanh thy lc ng m ca cng lm cho vic iu khin vn hnh ca ny thun li v t tin cy cao, khi cn thit c th tin ti t ng ho ng m.

    3.3.3. Ca sp t ng bng i trng Nhng ca van ny c c trng l c s tham gia ca i trng, lm cn bng vi

    trng lng ca. C th phn ra 3 loi khc nhau: Loi cn bng pha trn, loi cn ngang v loi cn bng pha di (hnh 3-26, 3-27, 3-28).

    - Loi cn bng pha trn c th c hai trng hp: Mt l (hnh 3-26) i trng nm trn kh, c lm ni bi nc thng lu. Loi ny phi chn la cnh tay n v i trng sao cho trong mi v tr bt k ca ca vn m bo c tnh cn bng gi c mc nc dng cn thit. Hai l i trng c t trong 1 hm ca tr pin, vic ng m ca van c thc hin khi c s h tr bi lc y ni i trng ca nc cha y trong hm.

    - Loi cn bng ngang th i trng nm trong hm ring c cao trnh ngang vi ca van (hnh 3-27).

    - Loi cn bng pha di (hnh 3-28) vic gn vi i trng khng phi u ca van m hng lot im trung gian nh s lin kt khp quay ca trc ca van vi nhiu cnh tay n ca i trng. h ca van, phi cho nc vo bung i trng lm i trng ni ln, ca s h xung. Loi ca ny phc tp nn t s dng.

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  • 80 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    Hnh 3-26. Ca sp i trng pha trn

    Hnh 3-27. Ct ngang ca sp i trng ngang

    ( p dng ca x ct Lng)

    www.vncold.vn

  • Chng 3 - ca van phng 81

    MNTL

    0.54

    1.40

    30

    0.91

    Hnh 3-28. Ca sp c i trng pha di

    3.3.4. Ca Clape phao (gi tt l ca sp phao)

    a) Cu to

    Ca sp phao khc vi ca sp thng ch bn thn ca l 1 phao kn bng thp hoc bng vt liu tng hp. C l bm nc ra v c l bm nc vo.

    b) Nguyn l vn hnh

    - Khi cn h ca tho l th bm nc vo bng phao, ca van s t h xung nh trng lng bn thn v trng lng nc trong phao.

    - Khi cn ng ca th bm ht ht nc trong bng ca v ca s ni ln nh lc y ni ca ca.

    - iu kin ng ca:

    [ ]f G 1W G V .K> - ; (3-31) Trong :

    Wf - sc y ni;

    G - trng lng ca;

    VG - th tch ca.

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  • 82 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    - iu kin m ca:

    ( )n c G f 2G G V W .K + - > ; (3-32)

    K1, K2 - h s an ton ly bng 1,11,15.

    Hnh 3-29. Ca sp phao

    c) Phm vi ng dng

    Loi ca ny c th lm vi khu din ln rng ti 30m v cao ti 8 10m. C th ng dng cho cc cng trnh ngn sng vng ng bng c chnh lch ct nc thng h lu khng qu ln. Tuy loi ca ny cha ng dng rng nhng y l loi ca c trin vng pht trin.

    3.4. Ca Clape trc trn (hnh 3-30) 3.4.1. Cu to

    L mt tm phng c th bng g hoc bng thp hoc vt liu tng hp c lin kt bi cc dm chnh ph ngang v ng. Ca van c treo vo cc quay t dm ngang pha trn hoc tr pin.

    3.4.2. Nguyn l lm vic Ca van Clape trc trn c t ng ng li ngn l hoc ngn triu nh

    trng lng bn thn v p lc nc h lu ln hn thng lu. Ca van c t ng m ra tiu l nh p lc nc thng lu ln hn p lc nc h lu do l rt hoc triu xung.

    3.4.3. Phm vi p dng

    Loi ca van ny c p dng nhiu cc cng di sng, bin. u im l t ng tiu l kp thi, t ng ngn triu ngn l nhanh nhy. Nhc im l khng

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  • Chng 3 - ca van phng 83

    iu tit c mc nc trong ng, hay ni ng hn l khng gi c mc nc trong ng v cng khng ly c nc t sng vo ng. Do vy loi ca ny thng dng ngn mn v tiu l pha sng, bin, cn pha trong ng li phi c ca phng gi nc. tng m khi tiu l c th m ca ly nc ngi ta lm i trng pha trn trc quay v gi l Clape i trng.

    Hnh 3-30. Dng ca Clape trc trn

    3.5. Ca qut 3.5.1. Phm vi ng dng

    Ca qut c dng nhiu trn cc p trn ca nh my thy in v ca cc cng trnh thy nng. Ca qut c dng trong iu kin cn thit s dng lc nc ng m.

    Ca qut c tit din ngang dng hnh qut, n quay quanh trc nm ngang, c gn cht vi p pha thng lu hoc h lu; mt phn hoc ton b ca van vo trong thn p, ca van chuyn ng c l nh c mt phn hoc ton b p lc nc.

    3.5.2. Cc loi ca qut Ca qut thng c cc loi sau:

    - Loi ca qut h chuyn ng nh tc ng thy lc

    - Loi ca qut kn chu tc ng thy lc

    + c trc quay thng lu;

    + c trc quay h lu.

    Loi ca qut hot ng do thy lc c th rng ti 60 65m v cao ti 9 10m.

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  • 84 s tay KTTL * Phn 2 - cng trnh thy li * Tp 4

    - Loi tc ng bng c gii v thy lc

    Ca qut c th tc ng bng c gii cng vi thy lc tng tnh ch ng

    khi vn hnh. Loi ny c nhp rng 40 50m v cao 8 9m.

    a) Ca qut h do tc ng thy lc (hnh 3-31)

    Ca qut c bn chn theo 2 mi v trc quay v pha h lu; cc ca ny h vo bng p nh tc dng ca trng lng bn thn (khi phn cch bung p lc vi thng lu) v nng ln di tc dng ca p lc nc thng lu (khi ni bung p lc vi thng lu). tng tnh ni ca ca van qut, cc kt cu mi y c th thm phao trong gc trn ca ca qut.

    -1.5

    0.0

    MNTL 5.5

    MNHL

    1

    2

    3

    4

    5

    7 6 8

    Hnh 3-31. Ca qut dng h

    1- bung p lc; 2- ng dn trong tr pin; 3- ging trong tr pin; 4- ng ni ging vi h lu; 5- ng vin knh ca my iu chnh (cn bng i trng v ni vi nh ca van v vi my nng); 6- rng rc nng ng vin knh; 7- m t nng ng (iu khin nh phao t phn vo ca bung); 8- m t th ng.

    b) Ca van qut kn trc thng lu (hnh 3-32)

    Ca van ng ca bng cch m van (4) thng vi thng lu, kho van (5) thng vi h lu, p lc nc thng lu tc dng ln bn mt (3) y ca qut ln ngn nc.

    - Khi cn m ca qut th ch vic ng van thng bung p lc vi thng lu (4)