Study on Bending Damage Constitutive Model and Mechanical Properties of Limestone Based on Acoustic Emission

Abstract

To reveal the mechanical characteristics and damage evolution mechanism of limestone in the bending process, the cumulative acoustic emission (AE) hits were used to define the damage variable, and the rock microbody hypothesis and the Weibull distributionfunctionwereappliedtofurtherimprovethedamagevariable.Meanwhile,thebendingdamageconstitutivemodelof limestone under three-point bending was developed based on the Lemaitre strain equivalence principle and the continuum damagetheory.Then,thethree-pointbendingtestwithacousticemissionmonitoringwascarriedouttoverifytherationalityand validityofthemodel.Resultsshowedthatthemodifieddamagevariable D hadanexponentialdistributionwiththestrainε,and the damage was mainly concentrated in the macrocrack propagation stage. Moreover, the bending neutral layer moved towards thecompressivezoneinthebendingdamageprocess.Thebendingneutrallayer,furthermore,movedslowlyasmalldistanceatthe initial stage of bending fracture but moved fast a long distance at the end stage of bending fracture. In addition, the bending damageconstitutivemodelcouldbequantitativelyexpressedbythecumulativeAEhits Np,thestressσ,thestrainε,andYoung’s modulus E. The theoretical stress-strain model curves agreed well with experimental results, which demonstrated that the proposed model could capture the damage evolution of limestone reasonably in the bending process.