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【英文标准名称】:StandardGuideforUsingtheGravityMethodforSubsurfaceInvestigation
【原文标准名称】:重力法探测地下的标准指南
【标准号】:ASTMD6430-1999(2010)
【标准状态】:现行
【国别】:美国
【发布日期】:1999
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D18.01
【标准类型】:(Guide)
【标准水平】:()
【中文主题词】:
【英文主题词】:geophysics;gravity;microgravity;surfacegeophysics;Subsurfaceinvestigation--soil/rock;Gravitymethod
【摘要】:Concepts8212;Thisguidesummarizestheequipment,fieldprocedures,andinterpretationmethodsusedforthedeterminationofsubsurfaceconditionsduetodensityvariationsusingthegravitymethod.Gravitymeasurementscanbeusedtomapmajorgeologicfeaturesoverhundredsofsquaremilesandtodetectshallowsmallerfeaturesinsoilorrock.Insomeareas,thegravitymethodcandetectsubsurfacecavities.Anotherbenefitofthegravitymethodisthatmeasurementscanbemadeinmanyculturallydevelopedareas,whereothergeophysicalmethodsmaynotwork.Forexample,gravitymeasurementscanbemadeinsidebuildings;inurbanareas;andinareasofcultural,electrical,andelectromagneticnoise.Measurementofsubsurfaceconditionsbythegravitymethodrequiresagravimeter(Fig.1)andameansofdetermininglocationandveryaccuraterelativeelevationsofgravitystations.Theunitofmeasurementusedinthegravitymethodisthegal,basedonthegravitationalforceattheEarth''ssurface.TheaveragegravityattheEarth''ssurfaceisapproximately980gal.Theunitcommonlyusedinregionalgravitysurveysisthemilligal(10x2212;3gal).Typicalgravitysurveysforenvironmentalandengineeringapplicationsrequiremeasurementswithanaccuracyofafewx03BC;gals(10x2212;6gals),theyareoftenreferredtoasmicrogravitysurveys.Adetailedgravitysurveytypicallyusescloselyspacedmeasurementstations(afewfeettoafewhundredfeet)andiscarriedoutwithagravimetercapableofreadingtoafewx03BC;gals.Detailedsurveysareusedtoassesslocalgeologicorstructuralconditions.Agravitysurveyconsistsofmakinggravitymeasurementsatstationsalongaprofilelineorgrid.Measurementsaretakenperiodicallyatabasestation(astablenoise-freereferencelocation)tocorrectforinstrumentdrift.Gravitydatacontainanomaliesthataremadeupofdeepregionalandshallowlocaleffects.Itistheshallowlocaleffectsthatareofinterestinmicrogravitywork.Numerouscorrectionsareappliedtotherawfielddata.Thesecorrectionsincludelatitude,freeairelevation,Bouguercorrection(masseffect),Earthtides,andterrain.Afterthesubtractionofregionaltrends,theremainderorresidualBouguergravityanomalydatamaybepresentedasaprofileline(Fig.2)oronacontourmap.Theresidualgravityanomalymapmaybeusedforbothqualitativeandquantitativeinterpretations.AdditionaldetailsofthegravitymethodaregiveninTelfordetal(4);Butler(5);Nettleton(6);andHinze(7).ParameterBeingMeasuredandRepresentativeValues:Thegravitymethoddependsonlateralanddepthvariationsindensityofsubsurfacematerials.Thedensityofasoilorrockisafunctionofthedensityoftherock-formingminerals,theporosityofthemedium,andthedensityofthefluidsfillingtheporespace.Rockdensitiesvaryfromlessthan1.0g/cm3forsomevesicularvolcanicrockstomorethan3.5g/cm3forsomeultrabasicigneousrocks.AsshowninTable1,thenormalrangeislessthanthisand,withinaparticularsite,therealisticlateralcontrastsareoftenmuchless.Table1showsthatdensitiesofsedimentaryrocksaregenerallylowerthanthoseofigneousandmetamorphicrocks.Densitiesroughlyincreasewithincreasinggeologicagebecauseolderrocksareusuallylessporousandhavebeensubjecttogreatercompaction.Thedensitiesofsoilsandrocksarecontrolled,toaverylargeex...........
【中国标准分类号】:P10
【国际标准分类号】:07_060
【页数】:10P.;A4
【正文语种】:英语