水利电力英文翻译英文+中文ghkx.docx

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1、 OVEERFLLOW SPPILLLWAYYAn ooverrfloow sspilllwaay iis aa seectiion of damm deesiggnedd too peermiit wwateer tto ppasss ovver itss crrestt. OOverrfloow sspilllwaays aree wiidelly uusedd onn grraviity, arrch, annd bbutttresss ddamss. SSomee eaarthh daams havve aa cooncrretee grraviity secctioon ddesii

2、gneed tto sservve aas aa sppilllwayy. TThe dessignn off thhe sspilllwaay ffor toww daams is nott ussuallly criiticcal, annd aa vaarieety of simmplee crrestt paatteernss arre uusedd. IIn tthe casse oof llargge ddamss itt iss immporrtannt tthatt thhe ooverrfloowinng wwateer bbe gguidded smooothhly ove

3、er tthe creest witth aa miinimmum of turrbullencce. If thee ovverfflowwingg waaterr brreakks cconttactt wiith thee sppilllwayy suurfaace, a vaccuumm wiill forrm aat tthe poiint of sepparaatioon aand cavvitaatioons mayy occcurr. CCaviitattionns ppluss thhe vvibrratiion froom tthe altternnatees mmakii

4、ng andd brreakkingg off coontaact bettweeen tthe watter andd thhe ffacee off thhe ddam mayy reesullt iin sseriiouss sttruccturral dammagee.Caviitiees ffillled witth vvapoor, airr, aand othher gasses willl fformm inn a liqquidd whheneeverr thhe aabsoolutte ppresssurre oof tthe liqquidd iss cllosee to

5、o thhe vvapoor ppresssurre. Thiis pphennomeenonn, ccaviitattionns, is likkelyy too occcurr whheree hiigh vellociitiees ccausse rreduucedd prresssuree. SSuchh coondiitioons mayy arrisee iff thhe wwallls oof aa paassaage aree soo shharpply currvedd ass too caausee seeparratiion of floow ffromm thhe bb

6、ounndarry. Thee caavitty, on movvingg doownsstreeam, maay eenteer aa reegioon wwherre tthe abssoluute is mucch hhighher. Thhis cauusess thhe vvapoor iin tthe cavvityy too coondeensee annd rretuurn to liqquidd wiith a rresuultiing impplossionn, oor ccolllapsse, exttremmelyy hiigh preessuure ressultt.

7、 SSomee off thhe iimpllosiive acttiviity willl ooccuur aat tthe surrfacces of thee paassaage andd inn thhe ccrevvicees aand porres of thee boounddaryy maaterriall. UUndeer aa coontiinuaal bbombbarddmennt oof tthesse iimpllosiionss, tthe surrfacce uundeergooes fattiguue ffailluree annd ssmalll ppartt

8、iclles aree brrokeen aawayy, ggiviing thee suurfaace a ssponngy apppearrancce. Thiis ddamaaginng aactiion of cavvitaatioons is callledd piittiing.The ideeal spiillwway wouuld takke tthe forrm oof tthe undderssidee off thhe nnappped of a ssharrp-ccresstedd weeir wheen tthe floow rratee coorreespoonds

9、s too thhe mmaxiimumm deesiggn ccapaacitty oof tthe spiillwway. Moore exaact proofilles mayy bee fooundd inn moore exttenssivee trreattmennts of thee suubjeect. Thhe rreveersee cuurvee onn thhe ddownnstrreamm faace of thee sppilllwayy shhoulld bbe ssmoooth andd grraduual; A raddiuss off abboutt onne

10、-ffourrth of thee sppilllwayy heeighht hhas proovedd saatissfacctorry. Strructturaal ddesiign of an ogeee sspilllwaay iis eesseentiiallly tthe samme aas tthe dessignn off a conncreete graavitty ssecttionn. TThe preessuure exeerteed oon tthe creest of thee sppilllwayy byy thhe fflowwingg waaterr annd

11、 tthe draag fforcces cauusedd byy flluidd frricttionn arre uusuaallyy smmalll inn coompaarisson witth tthe othher forrcess acctinng oon tthe secctioon. Thee chhangge iin mmomeentuum oof tthe floow iin tthe vicciniity of thee reeverrse currve mayy, hhoweeverr, ccreaate a fforcce wwhicch mmustt bee co

12、onsiiderred. Thhe rrequuireemennts of thee oggee shaape usuuallly nneceessiitatte aa thhickker secctioon tthann thhe aadjaacennt nno ooverrfloow ssecttionns.A saavinng oof cconccrette ccan be efffectted by prooviddingg a proojecctinng ccorbbel on thee uppstrreamm faace to conntrool tthe floow iin oo

13、utllet connduiits thrrouggh tthe damm, aa coorbeel wwilll innterrferre wwithh gaate opeerattionn.The disschaargee off ann ovverffloww sppilllwayy iss giivenn byy thhe wweirr eqquattionnWherre QQ=diischhargge, or L=cooeffficiientth=heead on thee sppilllwayy (vvertticaal ddisttancce ffromm thhe ccress

14、t oof tthe spiillwway to thee reeserrvoiir lleveel), mThe coeeffiicieent varriess wiith thee deesiggn aand heaad. Expperiimenntall moodells aare oftten useed tto ddeteermiine spiillwway coeeffiicieent. Ennd cconttracctioons on a sspilllwaay rreduuce thee efffecctivve llenggth bellow thee acctuaal ll

15、enggth L. Squuaree-coorneeredd piierss diistuurb thee fllow connsidderaablyy annd rreduuce thee efffecctivve llenggth by thee wiidthh off thhe ppierrs ppluss abboutt 0.2h forr eaach pieer.Streeamlliniing thee piierss orr fllariing thee sppilllwayy enntraancee miinimmizees tthe floow ddistturbbancce.

16、 If thee crrosss-seectiionaal aareaa off thhe rreseervooir jusst uupsttreaam ffromm thhe sspilllwaay iis llesss thhan fivve ttimees tthe areea oof ffloww ovver thee sppilllwayy, tthe appproaach vellociity witth iincrreasse tthe disschaargee a notticeeablle aamouunt. Thhe eeffeect of appproaach vello

17、ciity cann bee acccouunteed ffor by thee eqquattionnwherre iis tthe appproaach vellociity.PROPPERTTIESS OFF COONCRRETEE Thee chharaacteerissticcs oof cconccrette sshouuld be connsiddereed iin rrelaatioon tto tthe quaalitty ffor anyy giivenn coonsttrucctioon ppurpposee. TThe cloosesst ppraccticcablle

18、 aapprroacch tto pperffecttionn inn evveryy prropeertyy off thhe cconccrette wwoulld rresuult in pooor eeconnomyy unnderr maany conndittionns, andd thhe mmostt deesirrablle sstruuctuure is thaat iin wwhicch tthe conncreete hass beeen dessignned witth tthe corrrecct eemphhasiis oon eeachh off thhe vv

19、ariiouss prropeertiies of thee cooncrretee, aand nott soolelly wwithh a vieew tto oobtaainiing, saay, thee maaximmum posssibble strrenggth. Althhouggh tthe atttainnmennt oof tthe maxximuum sstreengtth sshouuld nott bee thhe ssolee crriteerioon iin ddesiign, thhe mmeassureemennt oof tthe cruushiing s

20、trrenggth of conncreete cubbes or cyllindderss prroviidess a meaans of maiintaainiing a uunifformm sttanddardd off quualiity, annd, in facct, is thee ussuall waay oof ddoinng sso. Sinnce thee ottherr prropeertiies of anyy paartiicullar mixx off cooncrretee arre rrelaatedd too thhe ccrusshinng sstree

21、ngtth iin ssomee maanneer, it is posssibble thaat aas aa siinglle cconttroll teest it is stiill thee moost connvenniennt aand infformmatiive.The tesstinng oof tthe harrdenned conncreete in preefabbriccateed uunitts ppressentts nno ddiffficuultyy, ssincce ccompplette uunitts ccan be sellectted andd b

22、rrokeen iif nneceessaary in thee prroceess of tesstinng. Sammplees ccan be takken froom ssomee paartss off a finnishhed strructturee byy cuuttiing corres, buut aat cconssideer oone cosst aand witth aa poossiiblee weeakeeninng oof tthe strructturee. IIt iis ccusttomss, ttherrefoore, too esstimmatee t

23、hhe ppropperttiess off thhe cconccrette iin tthe strructturee onn thhe ooasiis oof tthe tessts madde oon sspeccimeensmmounndedd frrom thee frreshh cooncrretee ass itt iss pllaceed. Theese speecimmenss arre ccomppactted andd cuuredd inn a staandaard mannnerr giivenn inn BSS 18881 in 19770 aas iin tth

24、esse ttwo resspeccts it is impposssiblle tto ssimuulatte eexacctlyy thhe ccondditiionss inn thhe sstruuctuure. Siincee thhe ccrusshinng sstruuctuure is alsso aaffeecteed bby tthe sizze aand shaape of a sspeccimeen oor ppartt off a strructturee, iit ffolllowss thhat thee crrushhingg sttrenngthh off a

25、 cubbe iis nnot neccesssaryy thhe ssamee ass thhat of thee maass of exaactlly tthe samme cconccrette.Crusshinng sstreengtthConccrette ccan be madde hhaviing a sstreengtth iin ccomppresssioon oof uup tto aabouut 880N/,orr evven morre ddepeendiing maiinlyy onn thhe rrelaativve ppropporttionns oof wwat

26、eer aand cemmentt, tthatt iss, tthe watter/cemmentt raatioo, aand thee deegreee oof ccomppacttionn. CCrusshinng sstreengtths of bettweeen 220 aand 50 N/ at 28 dayys aare norrmallly obttainned on thee siite witth rreassonaablyy goood suppervvisiion, foor mmixees rrougghlyy eqquivvaleent to 1:22:4 of

27、cemmentt: ssandd: ccoarrse agggreggatee. IIn ssomee tyypess off prrecaast conncreete succh aas rraillwayy slleepperss, sstreengtths rannginng ffromm 400 too 655 N/ att 288 daays aree obbtaiinedd wiith ricch mmixees hhaviing a llow watter/cemmentt raatioo.The cruushiing strrenggth of conncreete is in

28、fflueenceed bby aa nuumbeer oof ffacttorss inn adddittionn too thhe wwateer/ccemeent rattio andd thhe ddegrree of commpacctioon. The morre iimpoortaant facctorrs aare Typee off ceemennt aand itss quualiity. Bothh thhe rratee off sttrenngthh gaain andd thhe uultiimatte sstreengtth mmay be afffectted.

29、Typee annd ssurffacee teextuure of agggreggatee. Therre iis cconssideerabble eviidennce to sugggesst tthatt soome agggreggatees pprodducee cooncrretee off grreatter commpreessiive andd teensiile strrenggthss thhan obttainned witth ssmoooth rivver graavells.Effiicieencyy off cuurinng. A looss in strr

30、enggth of up to aboout 40 perr ceent mayy reesullt ffromm prremaaturre ddryiing outt. CCuriing is theerefforee off coonsiiderrablle, impporttancce bbothh inn thhe ffielld aand in thee maakinng oof ttestts. The metthodd off cuurinng cconccrette ttestt cuubess giivenn inn BSS 18881 shoouldd, ffor thii

31、s rreasson, bee sttricctlyy addherred to.Tempperaaturre IIn ggeneerall, tthe ratte oof hharddeniing of conncreete is inccreaasedd byy ann inncreeasee teempeeratturee. AAt ffreeezinng ttempperaaturres thee crrushhingg sttrenngthh maay rremaain loww foor ssomee tiime.Age UUndeer nnormmal conndittionns

32、 iincrreasse iin sstreengtth wwithh agge, thee raate of inccreaase deppenddingg onn thhe ttypee off ceemennt wwithh agge. For insstannce, hiigh aluuminna ccemeent prooducces conncreete witth aa crrushhingg sttrenngthh att 211 hoourss eqquall too thhat of norrmall Poortllandd ceemennt cconccrette aat

33、 228 ddayss. HHarddeniing conntinnuess buut aat aa muuch sloowerr raate forr a nummberr off yeearss.The aboove refferss too thhe sstattic ulttimaate loaad. Whenn suubjeecteed tto rrepeeateed lloadds cconccrette ffaills aat aa looad smaalleer tthann thhe uultiimatte sstattic loaad, a ffatiiguee efffe

34、cct. A nuumbeer oof iinveestiigattorss haave esttabllishhed thaat aafteer sseveerall miilliion cyccless off looadiing, thhe ffatiiguee sttrenngthh inn coomprresssionn iss 500-600 peer ccentt off thhe uultiimatte sstattic strrenggth.Tenssilee annd fflexxuraal sstreengtthThe tennsille sstreengtth oof

35、cconccrette vvariies froom oone-eigghthh off thhe ccomppresssivve sstreengtth aat eearlly aagess too abboutt onne- tweentiiethh laaterr, aand is nott ussuallly takken intto aaccoountt inn thhe ddesiign of reiinfoorceed cconccrette sstruuctuuress. TThe tennsille sstreengtth iis, howweveer, of connsid

36、deraablee immporrtannce in ressisttingg crrackkingg duue tto cchanngess inn mooistturee coonteent or temmperratuure. Tenssilee sttrenngthh teestss arre uusedd foor cconccrette rroadds aand airrfieeldss.The meaasurremeent of thee sttrenngthh off cooncrretee inn diirecct ttenssionn iss diiffiicullt aa

37、nd is rarrelyy atttemmpteed. Two morre ppraccticcal metthodds oof aasseessiing tennsille sstreengtth aare avaailaablee. OOne givves a mmeassuree off thhe ttenssilee sttrenngthh inn beendiing, ussuallly terrmedd thhe fflexxuraal sstreengtth. BS 18881:119700 giivess deetaiils conncerrninng tthe makkin

38、gg annd ccuriing of fleexurre ttestt sppeciimenns, andd off thhe mmethhod tesst. The staandaard sizze oof sspeccimeen iis 115015007500 loong forr agggreegatte oof mmaxiimumm siize 40. If tthe larrgesst nnomiinall siize of thee agggreegatte iis 220, speecimmenss 100010007500 loong mayy bee ussed.A lo

39、oad is appplieed tthrooughh twwo rrolllerss att thhe tthirrd ppoinnts of thee sppan unttil thee sppeciimenn brreakks. The exttremme ffibeer sstreessees, thaat iis, commpreessiive at thee toop aand tennsille aat tthe botttomm, ccan theen bbe ccompputeed bby tthe usuual beaam fformmulaae. The beaam ww

40、illl obbvioouslly ffaill inn teensiion sinnce thee teensiile strrenggth is mucch lloweer tthann thhe ccomppresssivve sstreengtth. Formmulaae ffor thee caalcuulattionn off thhe mmoduuluss off ruuptuure aree giivenn inn BSS 18881:19770.Testt sppeciimenns iis tthe forrm oof bbeamms aare sommetiimess us

41、sed to meaasurre tthe modduluus oof rruptturee orr fllexuurall sttrenngthh quuickkly on thee siite. The twoo haalvees oof tthe speecimmen mayy thhen be cruusheed sso tthatt beesiddes thee fllexuurallstrrenggth thee coomprresssivee sttrenngthh caan bbe aapprroxiimattelyy deeterrminned on thee saame s

42、ammplee. TThe tesst iis ddesccribbed in BS 18881:119700.Valuues of thee moodullus of ruppturre aare utiilizzed in somme mmethhodss off deesiggn oof uunreeinfforcced conncreete roaads andd ruunwaays, inn whhichh reeliaancee iss pllaceed oon tthe fleexurralsstreengtth oof tthe conncreete to disstriibu

43、tte cconccenttratted loaads oveer aa wiide areea.Moree reecenntlyy inntrooducced is a ttestt maade by spllitttingg cyylinnderrs bby ccomppresssioon aacrooss thee diiameeterr, tto ggivee whhat is terrmedd thhe sspliittiing tennsille sstreengtth; Dettaills oof tthe metthodd arre ggiveen iin BBS 118811

44、:19970.Valuues of thee moodullus of ruppturre aare utiilizzed in somme mmethhodss off deesiggn oof uunreeinfforcced conncreete roaads andd ruunwaays, inn whhichh reeliaancee iss pllacee onn thhe fflexxuraal sstreengtth oof tthe conncreete to disstriibutte cconccenttratted loaads oveer aa wiide areea

45、.Moree reecenntlyy inntrooducced is a ttestt maade by spllitttingg cyylinnderrs bby ccomppresssioon aacrooss thee diiameeterr, tto ggivee whhat is terrmedd thhe sspliittiing tennsille sstreengtth; Dettaills oof tthe metthodd arre ggiveen iin BBS 118811:19970. thhe ttesttingg maachiine is fitttedd wi

46、ith an exttra beaarinng bbar to disstriibutte tthe loaad aalonng tthe fulll llenggth of thee cyylinnderr Pllywoood strripss, 112mmm wiide andd 3mmm tthicck aare inssertted bettweeen tthe cyllindder andd thhe ttesttingg maachiine beaarinng ssurffacees ttop andd boottoom.Fromm thhe mmaxiimumm apppliie

47、d loaad aat ffailluree thhe ttenssilee spplitttinng sstreengtth iis ccalcculaatedd ass foolloows:Wherre sspliittiing tennsille sstreengtth, N/P=maaximmum appplieed lloadd inn Nl=leengtth oof ccyliindeer iin mmm dd=diiameeterr inn mmm AAs iin tthe casse oof tthe commpreessiive strrenggth, reepeaatedd looadiing redducees tthe ulttimaate strrenggth so thaat tthe fattiguue ss