Development Of Evaluation Method And Evaluation System For Rock Microwave Irradiability

Microwave-assisted rock breaking technology has become a hot research topic in TBM tunneling for long tunnels.The new technology of combining microwave irradiation with mechanical rock breaking can greatly improve the excavation efficiency and reduce the wear rate of cutter head.The mineral composition of rocks,the inherent factors of rocks such as primary fractures,and environmental factors such as surrounding rock pressure are important factors that affect the effectiveness of rock microwave irradiation.To explore the quantitative analysis of objective factors such as mineral composition,primary fractures,and surrounding rock pressure that affect the weakening effect of microwave irradiation on rocks,and to develop a rock microwave irradiability evaluation system based on this.With the Control variates as the criterion,this paper uses the discrete element software PFC(Particle Flow Code)to conduct numerical simulation of microwave irradiation on six representative rocks with different relatively strong absorbing mineral content,different primary fracture parameters,and different surrounding rock pressure,And the influence rule on mechanical properties before and after microwave irradiation and TBM tool wear.F inally,the rock microwave irradiability evaluation system platform is constructed using HTML+CSS+JavaScript.The main research results of this paper are as follows:(1)During microwave irradiation of rocks,the initiation of cracks is located at the interface between relatively strong absorbing minerals and other minerals and is easy to occur at places where the microwave sensitivity of minerals differs sharply.The contact between internal particles is mainly tension damage,followed by compression damage,and the fracture is mainly transgranular cracks.When intergranular cracks occur around relatively strong absorbing minerals,they will turn and propagate,thus finding the shortest path interconnection with cracks in other parts of rocks.Its propagation along the interconnection path leads to cracking of other minerals along the way,resulting in a large number of transgranular cracks and a penetrating fissure network around relatively strong absorbing minerals.Damage of rock specimens after irradiation increases,peak strength and elastic modulus of uniaxial compression test decrease significantly,fluctuation of stress-strain curve increases,peak occurrence point advances and advance range increases,plastic stage of specimens becomes more obvious and toughness increases;The intensity of irradiated sample corresponds to the wear of TBM cutter with linear or quadratic function relation to the content of relatively strong absorbing minerals.Good function relation makes it possible to predict and judge the microwave irradiation effect of rock according to its mineral composition in practical engineering.(2)The effects of inclination,length and density of primary fissures on microwave-irradiated rock cracks are mainly manifested in that different inclination,length and density fissures have different local effects on the generation,propagation and interconnection path of cracks,and the formation of primary through-pass path is cut off in local area or secondary fissures are formed between primary fissures and microwave-irradiated rock to form long fissures and increase damage degree;Increasing the inclination,length and density of cracks makes the overall stress-strain curve undulating trend of rock specimens stronger after irradiation,the slope of stress-strain curve before peak value decreases,the compaction stage begins to appear and become more significant,the undulating degree and frequency after peak value is higher than before peak value,the peak strength decreases significantly,the plastic stage of specimens becomes more obvious and the toughness increases.The intensity of irradiated sample corresponds to the wear amount of TBM cutter,which has a linear or quadratic function relationship with the angle,length and density of primary crack.Good function relationship enables the prediction and judgment of microwave irradiation effect of rock according to the condition of primary crack in actual engineering.(3)Surrounding rock pressure can restrain the generation of cracks,reduce the number of cracks produced by microwave irradiation,reduce and shorten the width and length of cracks gathered by microwave irradiation,and significantly affect the fracture rate in various parts of rock and at the junction.Moreover,the growth regularity of microwave irradiation cracks under different surrounding rock pressure conditions is similar to each other,thus reducing the weakening effect of microwave irradiation on rock.The biaxial compression failure mode of rock before irradiation is X-shaped conjugated inclined shear failure,and the biaxial compression failure mode of rock after irradiation is marked shear failure of X-shaped conjugated inclined plane,which is formed continuously and extends on the basis of cracks generated by microwave irradiation.Compression stage exists in the stress-strain curve after irradiation compared with that before irradiation,the non-linear change stage before peak value increases significantly,the occurrence point of peak intensity is advanced and the post-peak strain stage is delayed.The intensity of irradiated sample corresponds to the wear of TBM cutter and the pressure of surrounding rock.Good functional relationship makes it possible to predict and judge the microwave irradiation effect of rock according to the pressure environment of surrounding rock in actual engineering.(4)A logically rigorous grading standard and evaluation system for rock microwave irradiability evaluation were established using the Analytic Hierarchy Process.The weight values of different influencing factors at each level were calculated,and the calculation criteria for rock microwave irradiability evaluation were established;The login interface,parameter input interface,and result output interface were constructed using HTML,CSS,and JavaScript,and a rigorous running logic was established.The details of webpage jumping and parameter calculation were improved,ultimately forming a rock microwave irradiability evaluation system platform.