Brazilian Splitting Test Of Rock Based On The Characteristics Of Micro Fabric

Rock is the main part of geological body.Because of its long geological process,there are a lot of microcracks in the rock,even obvious bedding,and the failure of the rock is mainly caused by the development and gradual development of microcracks.A large number of tests show that the failure forms and strengths of rocks with different mineral fabrics are obviously different.Therefore,it is of great significance to study the characteristics of rock mineral fabric and its failure mode and strength for further understanding of rock fracture mechanism.In this paper,the rock in the same direction is drilled and grouped by the method of mark sampling,and then the Brazilian split test is carried out.The surface structure of rock specimen is acquired by digital image technology,and then it is imported into the software PFC for in-situ modeling and numerical test.Due to the time-consuming and laborious indoor test,the spatial correlation function is introduced to characterize the rock structure.By giving different parameters to obtain images with different polymerization degree,component content,anisotropy and other characteristics,the granite structure with different occurrence states in nature is characterized.The numerical simulation is carried out for the granite with different structural parameters.At the same time,considering the influence of stress concentration and fracture development in the process of rock failure,fractal dimension is used to analyze the fracture network distribution in different failure stages of numerical simulation.The results show that:(1)there are obvious differences in the strength of rock specimens loaded in different directions,among which the difference between the maximum strength and the minimum strength is about 60%;(2)accurate construction can be carried out in PFC numerical software by using digital image,nuclear magnetic detection and other technologies;the numerical test results show that the strength of the specimen is related to the mineral fabric in the loading direction,and the size and area of the low strength structure are related to the strength of the specimen The results show that the strength of rock is higher when the degree of mineral aggregation is lower,and the strength of rock is higher when the content of low strength components in rock is lower;the more obvious the anisotropy of mineral fabric is,the greater the difference of strength is;the fracture fractal dimension(fracture fractal dimension)in different stages of rock failure process There is a certain relationship between the crack distribution and the rock strength.In the early stage of loading,the crack distribution of low-strength specimens is relatively concentrated,which is conducive to the occurrence of stress concentration.In the early stage of loading,the crack distribution of high-strength specimens is relatively scattered,with large fractal dimension,which is not conducive to the stress concentration.This research work has added some new conclusions for the mechanical properties and anisotropic characteristics of rocks.