Confining pressure effect on energy parameters of sandstones based on damage evolution

Thecharacteristicparameterscorrespondingtodamageevolutionstateofrockmaterialarecrucialtodesigning,predictingandmonitoringthestabilityofgeotechnicalengineering.Thecyclicloadingunloadingtriaxialcompressiontestsofsandstoneswereimplementedwithdifferentconfiningpressure,and thedamage evolution state were determined by the lateral strain method and the volumetric strain method,andtheenergyparametersphasedevolution,theenergyevolutionofcharacteristicpointscorrespondingtodamageevolutionstateandrelationwithconfiningpressure,wereanalyzedbasedondamage evolutionstate.Theresultshowedthat:withdifferentconfiningpressure,theenergyparametersincreased withtheincreaseofthestrainateachstagebeforethepre-peak;themutationoftheelasticstrainenergy andthedissipationenergyatpeakstresstransferredtopost-peakwiththeincreaseoftheconfiningpressure;theenergyparametersdecreasedtoleveloffatresidualstressstage.Theenergyparametershada powerfunctiondecreasewithconfiningpressureatthepointofσcc,andthedissipationenergydecreased toleveloffwiththeincreaseoftheconfiningpressure.Atthepointsofσci,σcdandσp,theenergyparametersincreasedlinearlywithconfiningpressure,andtherewassmallchangetrendofthedifferencebetweenthetotalinputenergyandtheelasticstrainenergywiththeconfiningpressureatthedifferentcharacteristicpoints,andtherelativedifferencebetweenthetotalinputenergyandtheelasticstrainenergywas minimum,andthetotalinputenergyconvertedintotheelasticstrainenergywasmaximumatpointσcd.