Subjects: Mechanics >> Basic Mechanics submitted time 2023-04-24 Cooperative journals: 《应用力学学报》
Abstract： In order to study the size effect of strength and deformation,fracture mechanisms and failure modes of columnar jointed basalts(CJBs)under compression,the images of CJBs with different sizes are constructed,and combined with the meso damage mechanics,statistical strength theory and continuum mechanics,based on the digital image processing of RFPA3D-CT software,the images of CJBs are transformed into finite element mesh models,and the mechanical parameters of joint and rock are given respectively,in which the heterogeneities of joint and rock are considered.Numerical tests of CJBs under compression are carried out to investigated the influences of lateral pressure and the directions(Ⅰ/Ⅱ)on mechanical size effect of CJBs.The stress field evolution and damaged fracture characteristics of CJBs during fracture are also revealed.The results show that for the direction Ⅰ orthogonal to column axis,when the lateral pressure is 0 MPa,the compressive strength(CS)of specimen is without no obvious size effect; when the lateral pressure is 2 MPa,the critical value of CS size effect of specimen is 4 m; when the lateral pressure is 4,6,8 MPa,this critical value is 6 m.For the direction Ⅱ orthogonal to column axis,when the lateral pressure is 0 MPa and 2 MPa,the CS of specimen has no apparent size effect; when the lateral pressure is 4 MPa,the critical value of CS size effect of specimen is 4 m; when the lateral pressure is 6 MPa and 8 MPa,this critical value is 6 m.When the lateral pressure is 0-8 MPa,with the increase of model size,the variation range of transverse anisotropy coefficient of CS is 0.75-1.15; that of equivalent deformation modulus(EDM)is 0.90-1.15.Therefore,the CJBs can be approximately transversely isotropic.The whole processes of joint cracking condition,stress concentration,crack initiation and propagation,fracture zone formation and acoustic emission(AE)characteristics of CJBs are analyzed under different lateral pressures,model sizes and the directions(Ⅰ/Ⅱ).
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