地质学基础岩石的工程性质

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1、Chapter3TheengineeringpropertiesofrockAsamaterial,thestudyonengineeringpropertiesofrockisveryimportsntforengineerswhetherinsurfaceengineering(suchasfoundationshighwaysandrailroads,damsandreservoirsslopes)orsubsurfaceengineering(suchastunneling,storagecaverns,

2、disposalchambers).Generallyspeaking,Themechanicalbehaviorofrocksdependonthephysicalcharacteristicsofrocks.Theengineersneedtonotonlymechanicalbehaviorofrockbutalsotheirresponsetoappliedloads,themechanicalbehaviorsofrocksorrockmassandtheinflueneeofgroundwaterto

3、theirbehaviorsareallthekeyproblemsforgeologicalengineers.§3-1Themainphysicalpropertiesofintactrock1Specificgravity(d$)Theratiobetweenthemassandthatofequalvolumeofwater(i.e.theratioofmassdensityandwaterdensity).ds=WsVs•pw2Watercontent(co):Theratiobetweenthewei

4、ghtofwaterandtheweightofsolid.Ww=」xl00%比3Bulkspecificgravity:Theratiobetweenthetotalweightandthetotalvolumeofrock厂一肥V(KN/m3)Mostsilicatemineralshavedensitiesbetween26KN/m3and32KN/m3.Becauseofthismostigneousandmetamorphicrockshavedensitiesbetween26KN/m3and32KN

5、/m3.Limestoneandothersedimentaryrocksusuallyhavesomewhatlowerdensities(20to26KNIm3)becausetheyhavesignificantporosity.Sedimentsgenerallyhavedensitiessimilartothisorlower.1Porosity(n)Theratiobetweenthevolumeofvoidspace(containingliquidsandorgases)andtotalvolum

6、e・V斤二二X100%V2Absorbability(吸水性)w⑷匕(常压下)3Softness(软化性)ChangeconditioninstrengthwhensaturatedwithwaterKP^saturated)0.75~1弱软化"-—P,(dry)—[<0.75强软化4Anti-frozenabilitydecliningdegreeofcompressingstrength(P、一PJthedifference片(beforetest}5Permeability(R):Themeasuremen

7、toftherateatwhichfluidswillflowthroughasaturatedmaterials.WewilldiscussthemeasurementsofpermeabilitylaterinthelectureofGroundwater.§3-2Mechanicspropertiesofrock一TheconceptofstressandstrainofrocksStressisdefinedasforceperunitarea.TheunitsofstressarePascals・Soi

8、lstressesaretypicallyinthekilopascalrange(kPa).RockstressesareusuallymeasuredinMegapascals(MPa).Aloadappliedtoamaterialresultsinastressatanypointwithinit.Stressesmaybe:Compressiveorsqueez