Description Of Heterogeneous Damage In Rock-Like Brittle Medium And The Spatially Distributed Effects

The heterogeneous damage evolution inside brittle rock media is the key to its unpredictable failure,which has attracted a lot of research and attention.There are numerous research results on the monitoring and characterization of heterogeneous damage inside such materials,both in terms of monitoring methods and observation results.Due to the non-uniformity and complexity of damage distribution at different scales,there is currently a lack of effective description,especially for the relationship between the evolution process and macroscopic response,and there is a lack of direct understanding and description methods.Based on this,this article will explore from two aspects: on the one hand,based on its internal damage monitoring,exploring a quantitative description method that combines its macroscopic evolution and failure process;On the other hand,the correlation between macroscopic mechanical response and failure process corresponding to damage spatial distribution will be examined by predicting damage with different spatial distributions.A high-precision CT in-situ observation experiment was conducted on the uniaxial compression failure process of granite to fully observe and analyze the damage evolution process leading to catastrophic failure of granite.Based on X-ray photographs,using Xray absorption and phase contrast imaging,three-dimensional volume reconstruction of the internal structure of the specimen was achieved.During the reconstruction process,some correction methods are used to remove sampling noise such as annular artifacts,correct the effects of changes in the intensity of the X-ray source in the experiment,and use a non-local average filter to reduce noise on the constructed three-dimensional volume.Based on high-precision X-ray absorption imaging,defect(containing air)voxels are separated from the solid,and a unified gray threshold is used to process the threedimensional image of each sample.Based on this,all damage defects(including voids,pores,and micro-cracks)in the sample during deformation under load are extracted.Based on the gray analysis of two-dimensional slices,the crack propagation law is studied.By defining the crack volume,surface area and fractal dimension in threedimensional state,the characterization and description of non-uniform damage defects in rock are realized.Based on this,through the analysis of the evolution characteristics of these parameters with the loading process of the test piece,the evolution characteristics and complexity of the non-uniform damage spatial network architecture are explained,and a method for characterizing the evolution characteristics of non-uniform damage is presented and analyzed in detail.Based on the similarity theory,rock-like specimens with different defect distributions were fabricated and the experimental process was designed.The experiment revealed the impact characteristics of the spatial distribution of damage defects on the macroscopic mechanical response and failure under the same damage degree.The greater the dispersion of the spatial distribution of damage,the smaller the elastic modulus of the material,and the different failure modes of prefabricated damage specimens were also different.The influence of defect spatial distribution on the evolution characteristics of deformation field was systematically analyzed,and the influence of defect distribution on the crack initiation position and propagation process was analyzed in detail.