Study On The Correlation Between Granite Mineral Composition And Fracture Property And Strength In The Surrounding Rock Of Deep Tunnel

The brittle rock mass is often accompanied by ejection in the process of deep underground engineering construction,engineering problems such as collapse,rock burst.Underground cavern excavation after energy release of the surrounding rock to produce a large number of cracks of rock mass,the expansion of the micro cracks,eventually lead to brittle failure of surrounding rock.Fracture properties of rock mass and its deformation and failure mechanism have close relations,are the important factors influencing the stability of surrounding rock.As a natural geological material,the internal mineral composition of rock mass is the mesoscopic basis for studying its mechanical behavior and fracture characteristics.Therefore,this paper takes granite as the research object,discusses the influence of diagenetic minerals on rock mechanical properties,and studies the stability of surrounding rock from the point of view of fracture mechanics.The main research contents of this paper are as follows:First of all,the collecting typical granite rock,ore by polarizing microscope X-ray appraisal analysis granite mineral composition,different regions based on the uniaxial compression test and double twist test basic mechanical parameters for each sample.Through regression analysis research granite mineral composition on its strength,fracture toughness and the influence of subcritical crack growth rule.The results showed that the quartz and plagioclase are the main factors,which heavily developed impacts the mechanical property of graniteSecondly,particle flow software PFC is used to simulate the double torsion test,which reflects the fracture characteristics of rock.The parameters were calibrated based on uniaxial compression tests,and the obtained mesoscopic parameters could match the physical and mechanical properties of rock well.The three-dimensional model is used to intuitively reflect the process of crack growth,and the crack form,crack growth law and peak load shown by the simulation are consistent with the laboratory test.The model can simulate the crack behavior with time in the double-torsion test,and it is an effective method to obtain the fracture toughness and subcritical crack growth law of rock.Finally,in order to han dhi nutrient-laden water conveyance project qinling tunnel as the background,simulate the excavation of the deep caverns under high geostress.The stress level of surrounding rock after excavation disturbance is put into the standard rock specimen with crack for simulation,and the crack propagation law of surrounding rock under stress concentration is obtained.