Experimental Research On The Strength Degradation Of Granite From Different Places Under Microwave Irradiation

Microwave irradiation of hard rock can be applied to mechanical crushers for auxiliary rock breaking,so as to extend the life of the cutter head and realize continuous and efficient mining,maximize the characteristics of mechanical rock breaking,and reduce the time of rock breaking and the cost of mechanical equipment damage.Rock types and irradiation parameters in the process of microwave-assisted rock breaking are important factors that affect the irradiation effect.Microwave irradiation of hard rocks in different regions has important theoretical and practical significance for the study of rock mineral composition,temperature effects and failure mechanisms,It is concluded through experimental research:(1)Qualitative and quantitative mineral composition and content of granite in different regions,and research the different response effects of granite in different regions due to the difference in mineral composition under microwave irradiation.The research shows that:Transcrystalline cracks appear under high-intensity microwave parameters,and the number of cracks increases with the increase of microwave irradiation intensity;The main diagenetic mineral content has not changed much,but the difference in mineral content will directly affect the rock degradation phenomenon,the more the rock contains biotite,pyroxene and quartz,the more obvious the damage under the same microwave irradiation parameters.(2)Through the thermal effect distribution results of granite surface,the temperature of the granite surface in the three regions was distributed in a ring shape,the temperature gradually decreases from the center of the rock to the edge in a radial and relatively uniform manner,and thermal expansion and squeeze failure occurs inside the rock during the heat transfer process;The microwave irradiation power increases,the surface temperature growth rate and temperature gradient increase greatly,rocks are more thermally fractured with an average temperature exceeding 500?.(3)Through the ultrasonic acoustic time test,calculate the longitudinal wave velocity and relative dynamic elastic modulus of the specimen.It was concluded that rocks increase with microwave power,the rate of change of the relative dynamic elastic modulus of granite in different regions is a process of rapid decline in the initial stage,slow decline in the middle stage,and accelerated decline in the later stage.Relative dynamic elastic modulus can more accurately determine the degree of rock damage after irradiation.(4)Through the Brazilian disc split test,Measure the compressive stress and calculate the tensile strength.It was concluded that the rock strength deteriorates more obviously with the microwave strength increases;Within a specific irradiation power range,the optimal irradiation parameter for Jiangxi Xingan granite is(6kW,3min),the optimal irradiation parameter for Zhangzhou granite,Fujian is(2kW,3min),and the optimal irradiation parameter for Henan Biyang granite is(6kW,2min),by comparing the fitting calculation and the test results,it is concluded that the optimal irradiation time of the specimens is between 2min and 4min,and it is verified that the shorter irradiation can achieve the effect of auxiliary rock breaking.Finally,a cubic curve of time and damage variables is fitted,and the time point at which the change rate of damage variable is zero is used as the reference point for rock optimization time.This article uses a combination of experiment and theory,is used to research the microscopic,thermal effect distribution,relative dynamic elastic modulus and tensile strength of granite in three regions under different microwave irradiation parameters,The effect of rock degradation is analyzed and a microwave irradiation parameter optimization scheme is proposed to provide certain theoretical guidance for the application of microwave technology.