Study On The Dynamic Properties Of Granite After Microwave Irradiation

For underground rock excavation engineering,"microwave+machinery" has broad application prospects,has become a new rock breaking technology,its research is mainly divided into two aspects,microwave irradiation damage,and mechanical properties and fracture characteristics of rock under mechanical impact,the existing literature did many research,but did not combine the two,make the research results are not comprehensive.Therefore,this paper attempts to explore the change of rock dynamic properties caused by microwave radiation.Use multi-mode cavity microwave equipment with 2450MHz and Hobkinson pressure rod device(SHPB)to conduct the impact compression test under different parameters and combine the stress strain curve to further verify the auxiliary effect of microwave technology on mechanical rock breaking method from the energy angle.The main research contents and conclusions are as follows:(1)Under the microwave power of 1.3kW?5.3kW,water loss of saturated granite is higher than water absorption,which indicates that the microwave radiation evaporates the water content of the rock surface no matter at high power or low power.When the water in the surface of the rock is lost,it evaporates mineral bound water,and the bound water will vaporize rapidly under the action of microwave and make the rock crack.(2)The microwave energy conversion rate of granite varies in the range of 13%?19%under each parameter,and the microwave energy conversion rate is lower as a whole.It is found that the damage variable increases the highest at 4 kW power and the microwave energy conversion rate increases,so the energy efficiency is the best when using 4 kW power irradiation.(3)The dynamic peak stress of granite in the range of 0 kW?5.3 kW increases with the increase of impact pressure.When the impact pressure level increases by 0.05 MPa,the peak stress will increase by 10%?20%,which is related to the damage of rock.After microwave radiation,the cracks in the rock cause certain damage,which leads to the reduction of the number of rock cyclic impact under the same impact pressure.(4)At different stages of stress-strain curve,rock has different deformation characteristics,and at the stage of rapid stress growth,there is no crack on the surface of the specimen,but it is compressed rapidly;In the stage of slow stress growth,axial cracks parallel to the compressive stress are produced on the surface of the specimen,and the cracks continue to expand;in the stage of stress decline,there is a slip phenomenon on the macro fracture surface of the rock,Obviously broken.(5)Under the same impact strength,the absorption energy per unit volume is the same.With the increase of the number of cycles,the energy absorbed by the rock is accumulated,which leads to the increase of the crack and the decrease of the peak compressive strength.At the same time,the proportion of absorbed energy increases after microwave irradiation,and the energy is saved.(6)The four parameters of the statistical damage constitutive model are simple and can basically reflect the whole stress-strain behavior during rock failure,The fitting error of most curves or falling,is very small.Except that the fitting error in the descending section of some curves is slightly larger,the fitting error in the ascending and descending sections of most curves is very small.In this paper,the change of rock dynamic properties caused by microwave radiation is explored tentatively,and the change law of rock dynamic properties,microwave irradiation power and impact pressure is summarized.This law plays a certain role in promoting the development of microwave-assisted rock breaking technology,At the same time,it also provides some theoretical reference for the development of future projects.