土木专业英语课件Lesson3

Lesson3Newwords1.col`loidal胶状的，胶体的，`colloid胶体2.sieven,v.筛，过筛，过滤3.samplen.vt.样品，取样specimen4.meshn.v网孔，网格，分网格5.`cumulativea.积累的；cumulate,cumulation6.gradingn.级配，等级；grade7.sedimentationn.沉淀;sediment8.suspensionn.悬浮；suspend~bridgecable-stayedbridge9.agitatev.搅动，混合；disturb10.hydrometern.（液体）比重计11.viscosityn.黏性；viscoidal12.flakyn.薄片状的，offlake13.pipetten.吸液管14.irrecoverablea.不可恢复的irretrievable15.concavea.凹的；convex凸的16.permeabilityn.渗透性;permeate,permeableseepseepagePhrasesandexpressions1.frostsusceptibility霜冻敏感性2.sievingmethod筛分法3.semi-logarithmiccurve半对数曲线4.gradingcurve级配曲线5.wetsieving湿法筛分6.dispersingagent分散剂7.Stoke’slaw斯托克定律8.unitweight重度9.coefficientofgrading级配系数10.sedimentationmethod沉降法11.particle-sizedistribution粒径分布TextParticleSizeAnalysis粒径分析Therangeofparticlesizesencounteredinsoilsisverywide:fromaround200mmdowntothecolloidalsizeofsomeclaysoflessthan0.001mm.在各种土中所遇到的粒径范围很大，大到200mm小到小于0.001mm的一些粘土胶粒。Althoughnaturalsoilsaremixturesofvarious-sizedparticles,itiscommontofindapredominanceoccurringwithinarelativelynarrowbandofsizes.尽管天然土都是由各种粒径的颗粒组成，但通常可发现其主要组成颗粒出现在一个比较小的粒径范围内。Whenthewidthofthissizebandisverynarrowthesoilwillbetermedpoorly-graded,ifitiswidethesoilissaidtobewell-graded.当这一粒径范围非常小时，称这种土级配较差，而当其较大时，称这种土级配良好。Anumberofengineeringproperties,e.g.permeability,frostsusceptibility,compressibility,arerelateddirectlyorindirectlytoparticle-sizecharacteristics.土的许多工程特性，如渗透性、霜冻敏感性、可压缩性等都直接或间接的与土的级配特性有关。Fig.3.1showstheBritishStandardrangeofpercentageofparticlesizes.图3.1为粒径百分数的英国标准范围。Theparticle-sizeanalysisofasoiliscarriedoutbydeterminingtheweightpercentagefallingwithinbandsofsizerepresentedbythesedivisionsandsub-divisions.通过确定落入由这些粒径分组和子组所代表的粒径范围的重量百分比，对土进行粒径分析。Inthecaseofacoarsesoil,fromwhichfine-grainedparticleshavebeenremovedorwereabsent,theusualprocessisasieveanalysis.对于粗粒土，它里面的细粒土被除去或本身就无细颗粒，常用的方法就是筛分法。Arepresentativesampleofthesoilissplitsystematicallydowntoaconvenientsub-samplesizeandthenoven-dried.此法是将要分析土的一代表样本系统地分为方便的子样本，然后烘干。Thissampleisthenpassedthroughanestofstandardtestsievesarrangedindescendingorderofmeshsize.再使烘干的土样通过一组筛孔尺寸由大至小放置的标准试验筛。Theweightofsoilretainedoneachsieveisdeterminedandthecumulativepercentageofthesub-sampleweightpassingeachsievecalculated.称量每个筛中剩下的土样的重量，并计算出通过每个筛的累计百分数。Fromthesefigurestheparticle-sizedistributionforthesoilisplottedasasemi-logarithmiccurve(Fig.3.2)knownasgradingcurve.根据这些数据，以半对数曲线的形式描出该土的粒径分布图，即所谓的级配曲线。细粒粗粒非常粗大颗粒粘土胶粒粉土砂砾石石块细中粗细中粗细中粗卵石块石Wherethesoilsamplecontainsfine-grainedparticles,awetsievingprocedureisfirstcarriedouttoremovetheseandtodeterminethecombinedclay/siltfractionpercentage.在土样中含有细土粒的场合，首先用湿筛分法将其除去，并确定粘粒/粉粒总共所占的分数。Asuitable-sizedsub-sampleisfirstoven-driedandthensievedtoseparatethecoarsestparticles(20mm).将一适量的分土样烘干，并过筛分开最粗的颗粒（20mm的颗粒）Thesub-sampleisthenimmersedinwatercontainingadispersingagentandallowedtostandbeforebeingwashedthrougha63m(micron)meshsieve.然后将土样浸入含有分散剂的水中，并在将其用63微米筛过筛前搁置起来（并将其搁置一会，再用63micron的筛子过筛）。Theretainedfractionisagainoven-driedandpassedthroughanestofsieves.将筛中保留的部分烘干，并用一组筛子过筛。Afterweighingthefractionsretainedoneachsieveandcalculatingthecumulativepercentagepassingeachsieve,thegradingcurveisdrawn.称量落在每个筛中土重，并计算出通过每个的累计百分数后，就可描出级配曲线。Thecombinedclay/siltfractionisdeterminedfromtheweightdifferenceandexpressedasapercentageofthetotalsub-sampleweight.Thecoarsestfraction(20mm)canalsobesievedandtheresultsusedtocompletethegradingcurve.由重量差确定粘粒/粉粒的总重，并将其表示为子土样总重的百分数。最粗的部分（即粒径20mm的部分）也可被过筛，并用其结果完成级配曲线的绘制。Afurthersub-divisionofparticle-sizedistributioninthefine-grainedfractionisnotpossiblebythesievingmethod.不能用筛分法对细粒部分的粒径分布作进一步分组。Aprocessofsedimentationisnormallycarriedoutforthispurpose.通常必须用沉降法实现此目的。Asmallsub-sampleofsoilisfirsttreatedwithadispersingagentandthenwashedthrougha63msieve.首先将一小子土样用分散剂进行处理，然后洗过63的筛子。Thesoil/watersuspensionisthenmadeupto500ml,agitatedvigorouslyforashortwhileandthenallowedtosettle.再从中取出500ml的土/水悬浮液，充分搅拌一会后让其沉降。TheprocedureisbasedonStoke’slaw,whichstatesthatthevelocityatwhichasphericalparticlewillsinkduetogravityinasuspensionisgivenby:此方法是基于斯托克思定律，即在重力作用下球形颗粒在某一悬浮液中下降的速度为Whered=diameterofparticle颗粒直径s=unitweightofthegrainofparticle颗粒重度w=unitweightofthesuspensionfluid(usuallywater)悬浮液的重度（通过为水的重度）=vescosityofthesuspensionfluid（悬浮液的黏度）Thediameterofthoseparticlesthatwillhavesettledagivendistanceinagiventime(t)maybeobtainedbyrearrangingEq.3.1:将式3.1变形得在给定时间t内，沉降一给定距离的那些颗粒的直径为Usuallyh=100mm,通常h=100mm,giving由此给出Samplestakenatadepthof100mm,atanelapsedtimeoft,willnot,therefore,includeparticlesofgreatersizethanthediameterdgivenbyEq.3.2;因此在，在深度100mm处，t时间后所取的悬浮液中将不会有粒径大于式3.2所给出的土粒;buttheproportionsofparticlessmallerthandinthesuspensionwillremainunchanged.但悬浮液中小于d的颗粒所占的比例仍保持不变。Theprocedureusingahydrometerconsistsofmeasuringthesuspensiondensityatadepthof100mmataseriesofelapsed-timeintervals.用液体比重计的方法包括以一系列时间间隔在深度100mm处测定悬浮液的比重。Thepercentage-finervaluescorrespondingtoparticulardiameter(i.e.particlesizes)areobtainedfromthedensityreadings,andthusagradingcurveforthefine-grainedfractionmaybedrawn.通过比重读数得到小于某一特定粒径的颗粒的百分数，从而可画出细粒部分的级配曲线。