Microscopic Numerical Experimental Study On Uniaxial Compressive Strength Of Heterogeneous Granite

The heterogeneity of rock mineral composition and microstructure is the root of the discreteness of rock mechanics parameters,and it is the essence of the anisotropy and size effect characteristics of rock mechanics.In this paper,based on the heterogeneity of rock materials,from the perspective of microscopic observation,granite is used as the research object,and the indoor uniaxial compression test is carried out.At the same time,the particle anisotropy and size are carried out by the particle discrete element software PFC^2D.The uniaxial compression numerical simulation experiment of the effect feature exploration analyzed the strength variation characteristics and deformation and failure characteristics of the specimen.The most of the research work and achievement are as follows:（1）An indoor uniaxial compression test was carried out on a group of homogenous granite specimens.The uniaxial compressive strength and elastic modulus of granite were obtained and numerical simulation was carried out based on the macroscopic mechanical parameters.The specimens were matched by meso-parameters.Finally,a set of mesoscopic parameters of the particle discrete element model matched with the granite indoor uniaxial compression test was obtained through the trial-and-error process.（2）In order to study the anisotropic characteristics of the uniaxial compressive strength caused by the distribution of mineral components in the same rock sample,this numerical test realizes the granite group by changing the random number of particle distribution in the case of the same fixed mineral component content.The change in the distribution.Based on the particle discrete element software PFC2D,based on the mesoscopic parameters of the above-mentioned calibrated granite numerical model,six sets of granite numerical models were constructed to ensure that only the particle distribution random numbers differ between different models,all other micromechanics The parameters were the same,and then a uniaxial compression simulation test was performed on six sets of numerical models.The test results show that the elastic modulus values of the six groups are less change,while the uniaxial compressive strength values are different,with a maximum phase difference of 20.4 MPa.It also shows that the mineral component distribution is different in the loading direction,and the uniaxial compressive strength value and its failure form of the model are also different.（3）In order to study the size effect characteristics of uniaxial compressive strength of granites with different sizes and mineral components,the same method was used to construct six sets of granite numerical models with fixed aspect ratio,specified mineral composition and different sizes.The uniaxial compression simulation test was carried out.The results show that the size effect of uniaxial compressive strength of granite numerical simulation model is quite significant.With the decrease of volume of numerical simulation model,the uniaxial compressive strength and elastic modulus of the model The values are increasing,and the increasing trend of the two is more consistent.It presents a nonlinear rise of the power-like function.The peak strain of the model fluctuates around a fixed value,and the amount of change is not large.It consists of three groups a1,b1,and c1.The experimental results of the numerical model show that even if the rock size is different,the physical and mechanical properties of the different size models can be made uniform by changing the content of the mineral components.