Study On Strength Deterioration Of Granite Under Different Microwave Irradiation Paths

With the development of economy,the exploitation and utilization of underground resources has gradually become a hot topic in society,and the fragmentation of hard rock is one of the problems that need to be solved urgently.As the traditional rock breaking method,mechanical rock breaking method and drilling and blasting method have the disadvantages of low rock breaking efficiency and high construction energy consumption.Therefore,after exploration and research,scientists put forward the method of microwave assisted mechanical rock breaking,which is of great significance to solve the problem of hard rock breaking.At present,many experimental studies on rock irradiated by microwave have been carried out,but there is no in-depth study on the damage mechanism and influencing factors of rock under microwave irradiation.Moreover,it is more scarce to study and discuss the test combined with simulation and macroscopic connection with mesoscopic.Based on this,in this paper,the damage mechanism and physical and mechanical properties of granite under different microwave irradiation paths are studied mainly by experiments and supplemented by numerical simulation.The main conclusions of the research are as follows:(1)Due to the different dielectric constant of minerals,the temperature distribution inside the rock is different.The stress between minerals after microwave irradiation is mainly produced between strong absorbing minerals and weak absorbing minerals.At the same time,the sensitivity of various minerals to microwave radiation is different,and the temperature variation amplitude is significantly different under the same microwave energy.Among them,biotite has the strongest sensitivity to microwave radiation,and quartz has the worst sensitivity to microwave radiation.(2)Under the condition of increasing energy,the surface temperature,longitudinal wave velocity,uniaxial compressive strength and static elastic modulus of the specimen have obvious periodic variation characteristics.When the irradiation time is increased to improve the microwave input energy,the microwave energy 480 kJ is taken as the dividing line,which is divided into two stages:rapid change and slow change.By increasing the radiation power to improve the microwave input energy,microwave energy594kJ as the dividing line,divided into slow change and fast change two ladder.(3)Under the condition of constant energy,although the microwave input energy is constant,the damage degradation amplitude of specimens under different irradiation paths is different.The damage degradation amplitude of specimens under high power and short time microwave irradiation paths is higher than that under low power and long time microwave irradiation paths.Therefore,under the condition of considering the effect and efficiency of microwave radiation,high power and short time microwave irradiation can be used to irradiate rock.(4)The ability of rock to resist impact load is reduced after microwave irradiation.With the increase of microwave input energy,this phenomenon is more and more obvious.The loss rate of dynamic compressive strength of the specimen after 180 s irradiation at 6 kW is up to 57.98%.However,compared with the change characteristics of static performance of specimens under uniaxial compression test,the dynamic performance of specimens under impact load has no obvious periodic change characteristics.(5)In the process of microwave-assisted rock breaking,firstly,the requirements of rock breaking should be clarified,and then the effect of microwave action should be analyzed according to the mineral composition and mineral content of rock.Finally,considering the actual microwave input mode in engineering,the best irradiation method should be selected for rock fracturing treatment,so as to improve the utilization rate of microwave energy and rock breaking effect in the process of rock breaking.