Study On The Influence Law Of Microstructure On Rock Weakening By Microwave Irradiation

The new rock breaking method of "microwave irradiation + mechanical rock breaking" can greatly improve the driving rate of machinery and reduce the wear of the knife disc.Diagenetic mineral type,shape,size and content and so on are important influence factors of microwave irradiation effect of weakening rock,to explore the rock mesoscopic structure of microwave irradiation effects,this paper uses many famous physical field analysis software COMSOL,conducting electromagnetic microwave irradiation weakening rock-temperature-force field coupling numerical simulation analysis,The effects of meso-structure on the electromagnetic field,temperature field,stress field and plastic zone of granite,pegmatite,limestone and marble during microwave irradiation were studied.Usually,the meso-structure of rock is summarized and abstracted,and an idealized simulation model of mineral particle group characteristics is established.The effects of particle group characteristics such as rock particle size,arrangement and content on microwaving weakened rock are studied.The main research results are as follows:(1)Granite,pegmatite,limestone and marble are all in uniform electric field under the same microwave incidence condition.Under the same microwave irradiation condition,the metamorphic rocks transmit more electromagnetic waves.Although the electric field intensity of granite and pegmatite in the microwave irradiation process is equal,the electromagnetic work loss capacity of granite is stronger than that of pegmatite.Marble has the weakest electromagnetic work loss capacity.No matter what kind of rock,minerals with strong dielectric properties inside the rock also have a strong electromagnetic work loss capacity.(2)The temperature distribution inside the rock is related to the electromagnetic work loss of minerals.Minerals with strong electromagnetic loss capacity have high temperature in the microwave irradiation process,and the temperature difference mainly appears at the interface of absorbing minerals and permeable minerals.The greater the microwave irradiation power,the more significant the temperature difference is,and the more conducive to the weakening of the rock.The electromagnetic power loss ability of igneous rocks is stronger than that of sedimentary rocks and metamorphic rocks,so the temperature of igneous rocks after microwave irradiation is higher than that of sedimentary rocks and metamorphic rocks.(3)There are two main forms of thermal stress in the process of microwave irradiation of rocks.The first type of thermal stress is mainly caused by the thermal stress concentration phenomenon caused by the temperature difference of mineral interface,and the other type of thermal stress is caused by the temperature gradient inside mineral.When the value of thermal stress exceeds the yield strength of the mineral inside the rock,plastic failure is formed there.With the increase of microwave irradiation time,the plastic failure area gradually expands and evolves.Since the structural integrity of metamorphic rocks and igneous rocks is higher than that of sedimentary rocks,there are less damage areas formed by metamorphic rocks and igneous rocks after microwave irradiation,which are respectively marble 7%,pegmatite 12.4%,granite38.6%,and limestone which belongs to sedimentary rocks 73.4% at most.In the process of microwave irradiation,the initial temperature of plastic failure is different due to different lithologies.The initial temperature of plastic deformation is 51? for limestone,77? for granite,148? for pegmatite,and 134? for marble.(4)The temperature inside the rock increases with the diameter of the absorbing mineral particles,and the temperature difference inside the rock increases with the diameter of the absorbing mineral particles.When the diameter of the mineral particles is 2mm,the temperature difference inside the rock is 44.9?,which contributes more significantly to the weakening of the rock.When the diameter of mineral particles is 2mm,the plastic failure zone formed in rock is at most 74.3%.When the content of absorbing minerals increases from 5% to 20%,the temperature difference in the rock is 25.3?,40.2?,53.1? and 71.3?,respectively.The increase of the content of absorbing minerals is more conducive to rock failure.