Dredging EngineeringPart 2 soil 疏浚工程 土质篇.docx
- 文档编号:9335670
- 上传时间:2023-02-04
- 格式:DOCX
- 页数:36
- 大小:676.51KB
Dredging EngineeringPart 2 soil 疏浚工程 土质篇.docx
《Dredging EngineeringPart 2 soil 疏浚工程 土质篇.docx》由会员分享,可在线阅读,更多相关《Dredging EngineeringPart 2 soil 疏浚工程 土质篇.docx(36页珍藏版)》请在冰豆网上搜索。
DredgingEngineeringPart2soil疏浚工程土质篇
Part2 DredgingProcess..........................................................................................................1
Chapter1BasicConceptsofSoilMechanics........................................................................................1
1.1SoilClassification...............................................................................................................1
1.2SoilProperties....................................................................................................................1
1.2.1PhaseRelationshipsofSoil..........................................................................................................2
1.2.2Compactionand/orConsistency.......................................................................................................2
1.2.3Permeability........................................................................................................................2
1.3 ElementarySoilTests............................................................................................................7
1.3.1PermeabilityTest....................................................................................................................7
1.3.2MohrCircle..........................................................................................................................8
1.3.3CaseStudy..........................................................................................................................10
1.3.4TriaxialShearTest---MohrFailureEnvelop..........................................................................................12
1.3.5DirectShearTest---Coulomb’sLaw(1776)...........................................................................................13
1.3.6StandardPenetrationTest--SPT......................................................................................................16
1.4 PassiveandActiveFailure—Rankine’sTheoryofLateralEarthPressure..................................................17
1.4.1ActiveStressState.................................................................................................................18
1.4.2PassiveStressState................................................................................................................20
1.5 StressesintheSubsoil.........................................................................................................20
1.5.1General.............................................................................................................................20
1.5.2DeterminationofVerticalStresses..................................................................................................22
1.5.3OverstressedorUnderstressedPoreWaterinaClayLayer............................................................................24
1.6Consolidation......................................................................................................................25
Acknowledgements..........................................................................................................................25
Part2 DredgingProcess
Chapter1BasicConceptsofSoilMechanics
1.1SoilClassification
Theobjectofsoilclassificationistodividethesoilintogroupssothatallthesoilsinaparticulargrouphavesimilarcharacteristicsbywhichtheymaybeidentified.Inpractice,therearemanydifferentclassificationsareusedbydifferentinstitutions,mostoftheseclassificationsystemsarebasedontheoutcomeoftheparticlesizedistributionanalysesandtheresultsoftheplotsontheplasticitychartofCasagrande.Table1-1istheinternationallymostacceptedstandardizationofparticle-size-ranges.
Table1-1Internationallymostacceptedstandardizationofparticle-size-ranges.
fine-grained
coarse-grained
Clay
Silt
sand
gravel
stone
Colloids
fine
2~6
medium
6~20
Coarse
20~60
fine
60~200
medium
200~600
coarse
600~2mm
fine
2~6
medium
6~20
coarse
20~60
cobbles
60~200
boulders
200~
μm(micron)
mm
Table1-2showstheBritishSoilClassificationSystemforEngineeringpurpose(BS5930,1981).Thenameanddescriptivelettersusedinthissystemareexplainedintable1-3.
1.2SoilProperties
1.2.1PhaseRelationshipsofSoil
Soilisamultiphasesystem,containingthreedistinctphases:
solid,liquid(water)andgas(air).Inrealitytheporesinbetweenthesolidparticlesarefilledwithwaterand/orgas,figure1-1(a);however,inordertodefinethephaserelationships,anelementofsoilisschematizedinfigure1-1(b).
1.2.2Compactionand/orConsistency
Fornaturaldepositsofsoilsthecompactionoftheencounteredlayerin-situisanimportantfeature.Thecompactionofanin-situsandlayerdependsonlargelyontheparticlesizedistribution(figure1-2),themodeofsedimentationandthestresshistory.Forclaysthecompactionmoreorlessdependsonthesamefeaturesbutissomewhatmorecomplicatedbecauseforclaystheinteractionbetweenclayparticlesdependsalsoontheelectricalchargesonthesurfaceoftheparticles.Thereforeitiscommonpracticetodistinguishthenotationcompactionforgranularsoils,whichisexpressedintherelativedensityDrandthenotationconsistencyforcohesivesoils,whichisexpressedintheunstrainedshearstrengthCu.Seetable1-4.
1.2.3Permeability
Thepermeabilityofthesoildeterminestherateofingressofwaterintothesoil,eitherbygravitationalfloworbydiffusion.Sincetheindividualsandparticlesarenotbondedtogetherbyhydratedwaterandsincetheparticlesarerelativelylarge,thereisaneasyaccessofwaterintothepores.Thereforesandhasagoodpermeability(permeabilityvariesbetweenk=10-2mm/sandk=10-4mm/s).However,claysarealmostimpermeable(permeabilityvariesbetweenk=10-6mm/sandk=10-8mm/s).Thetwomainreasonsforthisverylowpermeabilityare:
(1)theparticlesareverysmalli.e.ofcolloidalsize;
(2)thewatersurroundingtheclayparticlesispartlyhydratedand/orelectricallybondedtotheparticleandthereforetheflowofwaterenteringtheporesisverydifficult.
Permeabilityisanimportantsoilpropertythatvariesconsiderablyfordifferenttypesofsoils,asshownintable1-5.Relationsbetweensoiltypeandsoilparametersarelistedintable1-6.
Table1-2BritishSoilClassificationSystemforEngineeringPurposes
Table1-3Namesanddescriptivesymbolsforgradingandplasticitycharacteristics,usedintheBritishSoilClassificationSystemforEngineeringpurposes.
Component
Mainterm
Symbol
Qualifying
Symbol
Coarse
Gravel
Sand
G
S
Wellgraded
Poorlygraded
Poorlygraded,uniform
Poorlygapgraded
W
P
Pu
Pg
Fine
Finesoil,fines
Silt(M-soil)
Clay
F
M
C
Lowplasticity
Intermediateplasticity
Highplasticity
Veryhighplasticity
Extremelyhighplasticity
L
I
H
V
E
Organic
Peat
Pt
Organic
O
Fig.1-2Particlesizedistribution
Table1-4
Compactionofgranularsoils
Consistencyofcohesivesoils
classification
Dr
Classification
Cu[kN/m2]
Veryloose
Loose
Mediumdense
Dense
Verydense
0<15
15-35
35-65
65-85
85-100
Verysoft
Soft
Firmormedium
Stiff
Verystifforhard
<20
20-40
40-75
75-150
>150
Table1-5
Table1-6RelationbetweensoiltypeandsoilparameterstoNEN6740.
1.3 ElementarySoilTests
1.3.1PermeabilityTest
Alreadyinthemiddleofthe19thcentury(1850’s)Darcyexperimentallyfoundhisfamouslaw,whenhestudiedtheflowpropertiesofwaterthroughasand-filter-bed.Forhisexperimentsheusedaset-upsimilartothatshowninFig1-3,withwhichhecouldvarythelength(L)ofthesampleandthewaterpressuresatthetopandatthebottom.
Darcyexperimentallyfoundthatthearteofflow(Q)isproportionaltothefallofhead:
Andinverselyproportionaltothelength(L)ofthesample:
SinceQdenotesthetotaldischarge[m3/s]passingthroughthecross-sectionalarea A[m2]ofthesamplecontainer,itwillbeclearthatthespecificrateofthefloworspecificdischarge(q)hasthedimensionofavelocity[m/s]andalsorepresentsthevelocityvofthefreewaterinthetubewherethereisnosand.
Thereal(average)velocitywithwhichthewaterpassestheporechannelsinsidethesandsampleiscalledtheseepagevelocity(Vs)andcanbedefinedbyusingtheprincipleofcontinuity.Thedischargeofwaterpassingthetotalarea(A)abovethesandsampleperunittimemustalsopassthereducedaveragearea (Ap)oftheporechannelsinthesametime:
or
Theconstant(k)usedintheformulaaboveisthecoefficientofpermeabilitywhichhasthedimensionofavelocity[mm/s]andisanimportantsoilpropertywhichvariesconsiderablyfordifferenttypesofsoils,asshowninTable1-5.Itshouldbenotedthatkvaluesstrictlyapplytowater(200C).Allotherliquidswillhaveothervaluesforthepermeationconstant,dependingontheviscosity.
Fig.1-3Determinationofthecoefficientofpermeability
1.3.2MohrCircle
Inalmostallsoilmechanicsandfoundationengineeringproblems,whereconcentratedloadsareapplied,thehorizontalandverticalstresscomponentswillnotbeprincipalstresses:
i.e.alsoshearstresseswillactonthehorizontalandverticalplanes.
Fig1-4 Determinationofforcesactingonaninclinedplane
Asamatteroffactspeakingofthe“stressstate”inapointofthesubsoilismeaningless,withoutmentioningtheorientationoftheplaneofinterestonwhichtheforcesact.Thereforethecompl
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Dredging EngineeringPart soil 疏浚工程 土质篇 疏浚 工程 土质