不同三轴应力途径下红砂岩力学特性试验研究

不同三轴应力途径下红砂岩力学特性试验研究Abstract：Thestrengthanddeformationcharacteristicsofredsandstoneunderdifferenttriaxialstressstateswerestudiedbycompressionandstraintestingunderdifferentialtriaxialstress.Theresultsshowthatthestrengthanddeformationcharacteristicsofredsandstonearesignificantlyaffectedbythetriaxialstressstate.Thefailuremodeofredsandstonechangesgraduallyfrombrittlefracturetoductiledeformationwiththeincreaseofconfiningpressure.Thepeakstrengthofredsandstoneincreaseswiththeincreaseofconfiningpressure,andthefailuremodeofredsandstonechangesfrombrittlefracturetoplasticdeformation.Thedrainedtriaxialcompressiontestresultsshowthatthestress-straincurveofredsandstoneishighlynon-linearunderdifferenttriaxialstressstates.Thestress-straincurveofredsandstoneunderdifferenttriaxialstressstatesisdifferent.Inthetest,whentheaxialstressislessthanthepeakstressofredsandstone,thedeformationofredsandstoneismainlycausedbytheslipdeformationbetweenparticles.Whentheaxialstressexceedsthepeakstressofredsandstone,thedeformationofredsandstonemainlyoccursintheformofcracks.Keywords:redsandstone,triaxialstress,strength,deformationcharacteristics1.IntroductionRedsandstoneiswidelydistributedinnatureandplaysanimportantroleinthegeologicalandminingfields.Tostudythemechanicalpropertiesofredsandstoneundercomplexstressconditions,itisofgreatsignificanceforgeologicalresearchandminingengineering.Inthispaper,triaxialstresstestswerecarriedoutonredsandstonesamplesunderdifferentstressconditions,andthestrengthanddeformationcharacteristicsofredsandstoneunderdifferentstressconditionswerestudied.2.Experimentalprocedures2.1SamplecollectionTheredsandstonesamplesusedinthisexperimentwerecollectedfromaminingareainnorthernChina.Thesampleswerecollectedbycuttingoffthesurfacelayeroftherockusingadiamondsaw.Then,thesampleswereprocessedintostandardcylindricalsampleswithadiameterof50mmandaheightof100mm,andthesurfaceofthesampleswascarefullyprocessedtoensurethatthesampleshaveasmoothsurfaceandauniformdiameter.2.2ExperimentalapparatusThetriaxialstresstestswerecarriedoutusingaGDStriaxialstresstestsystem.Thesystemcancontroltheaxialandconfiningpressuresindependently.Theaxialpressurecanbeappliedusingaservo-hydraulicloadingsystem,andtheconfiningpressurecanbeappliedusingahigh-pressureoilpump.Thedeformationwasmeasuredusingadisplacementtransducer,andthepressurewasmeasuredusingapressuretransducer.2.3ExperimentalproceduresTheexperimentalproceduresmainlyincludethreeparts,namely,thedeterminationoftheuniaxialcompressivestrength,thedeterminationofthestrengthanddeformationcharacteristicsofredsandstoneunderdifferenttriaxialstress,andtheanalysisofthetestresults.2.3.1DeterminationofuniaxialcompressivestrengthThedeterminationoftheuniaxialcompressivestrengthiscarriedoutaccordingtotheGB/T50123-2019standard.Thecylindricalsamplesareplacedinacompressionmachine,andtheaxialloadisapplieduntilthesampleiscrushed.2.3.2DeterminationofstrengthanddeformationcharacteristicsofredsandstoneunderdifferenttriaxialstressThetestwascarriedoutunderdifferentconfiningpressures.Thetestconditionswereasfollows:theaxialstrainratewas0.0002/s,theconfiningpressurewas0MPa,2MPa,4MPa,and6MPa,respectively,andtheaxialloadingwasstoppedafterreachingthepeakstress.Theaxialstressandstrain,aswellastheconfiningpressure,weremeasuredduringthetest.2.3.3AnalysisoftestresultsTheaxialstress-straincurveswereobtainedbythetestdata.Thestress-strainrelationship,strength,deformationcharacteristics,failuremode,andotherparametersofredsandstoneunderdifferenttriaxialstresseswereanalyzed.3.Resultsanddiscussion3.1UniaxialcompressivestrengthofredsandstoneTheaverageuniaxialcompressivestrengthofredsandstonewas77.2MPa.3.2StrengthanddeformationcharacteristicsofredsandstoneunderdifferenttriaxialstressThepeakstressofredsandstoneincreaseswiththeincreaseofconfiningpressure,andthefailuremodeofredsandstonechangesfrombrittlefracturetoplasticdeformation.Thepeakstrengthofredsandstoneincreasesfrom99.9MPato128.3MPawiththeincreaseofconfiningpressurefrom0MPato6MPa.Theaxialstrainandconfiningpressurebothaffectthestrengthanddeformationcharacteristicsofredsandstone.Thetriaxialstressstatehasasignificantinfluenceonthedeformationandfailuremodeofredsandstone.Whentheaxialstressislessthanthepeakstressofredsandstone,thedeformationofredsandstoneismainlycausedbytheslipdeformationbetweenparticles.Whentheaxialstressexceedsthepeakstressofredsandstone,thedeformationofredsandstonemainlyoccursintheformofcracks.3.3AnalysisoftestresultsThetriaxialtestresultsshowthatthestress-straincurveofredsandstoneishighlynon-linear.Thestress-straincurveofredsandstoneunderdifferenttriaxialstressstatesisdifferent.Thedeformationbehaviorofredsandstoneunderdifferenttriaxialstressstatesissignificantlydifferent.Undertheconditionofhighconfiningpressure,thedeformationmodeofredsandstoneischaracterizedbyplasticdeformation.Thedeformationmodeofredsandstonechangesfrombrittlefracturetoplasticdeformationwiththeincreaseofconfiningpressure.4.ConclusionThestrengthanddeformationcharacteristicsofredsand