Study On The Cutting Mechanism Of Hard Rock By ODC Disk-cutter Technology

At present,there are still some problems in mechanical tunneling technology,such as narrow cutting range,poor geological adaptability and low reliability of equipment accessories.In order to study the design method of high-efficiency cutting mode and the mechanism of hard rock breakage,based on the analysis of the cutting motion characteristics of ODC cutter,this paper studied the cutting mechanical behavior law of impact cutting from the aspects of theoretical model,numerical simulation and experimental design,and discussed the rock breakage mechanism.The main work and conclusions are as follows:By analyzing the motion law of the ODC disc-cutter,it is found that the eccentric ratio R_E and the speed ratio R_V are the main parameters affecting the ODC cutter movement.When the R_E increases,the movement area of the cutter head becomes larger and larger,and as the R_V increases,the movement path of the cutter head becomes more and more gentle.According to the motion law of the ODC cutter,use the Griffith theory as the strength criterion,and the cutting force model is established.The average cutting force F of the cutter increases with the increase of R_E and R_V,and is significantly affected by R_V.The mean torque M increases with the increase of R_E,increases first and then decreases with the increase of R_V,and reaches the maximum when R_V=1.It is found that the contact angle（halfΨ）of the cutter-rock,and the instantaneous cutting force F_C increases with the increase of R_E.But considered the greater the eccentricity,the greater the torque,so actually design the value of the R_E is 0<R_E<0.1.However,with the increase of R_V,the impact of the R_V increases,and the impact of the cutterhead will be weakened.When R_V>1,theΨand F_C remain basically unchanged,in order to obtain a stable rock cutting mode.The design R_V has a value range of 0<R_V<1.With the uniaxial compressive strength,the Brazilian splitting strength,elastic modulus,poisson’s ratio,contrast parameter typeⅠfracture toughness of red sandstone,limestone,granite rock specimen,rock model is established in the software PFC3D.Through the simulation cutting experiment of ODC cutter,it is found that the cutting load increases with the increase of R_E and R_V.The number of cracks in the rock model is more obvious with the increase of R_E than with the increase of R_V,while the energy consumption of cutting ratio is more obvious with the increase of R_V than with the increase of R_E.For different cutting depths（d）,the specific energy（SE）has a good linear correlation with the elasto-plastic mechanical properties of rocks(brittleness index B3,fracture toughness K_Ic,elastic modulus E),and the difficulty of rock cutting is proportional to the brittleness characteristics of rocks.By comparing the simulation results with the theoretical model results,it is found that the load variation rules obtained by the theoretical model are consistent with the simulation rules,among which the two results about parameters R_V and d are relatively close in numerical value,while the two results about parameters R_E are quite different.ODC cutter cutting test device was designed and simulated cutting tests of coal sample and red sandstone were carried out.It is found that with the increase of velocity ratio R_V,mean cutting force,mean torque,specific energy SE and particle size distribution index CI increase gradually.As the cutting thickness d increases,the mean cutting force,mean torque,and particle size distribution index CI increase gradually,while the specific energy SE decreases continuously.By comparing the theoretical results,simulation results and experimental results under various working conditions,it is found that there is a good linear correlation between the three results of cutting load（R²≥0.688）,and the theoretical results are very close to the experimental results in numerical value,while the numerical value of simulation results is relatively small.Based on the comprehensive cutting force characteristics and simulation mesoscopic process analysis,it is found that in this cutting mode,the rock crushing process is:firstly,in the short time of the contact of the cutter-rock,the internal stress of the rock is rapid due to the impact and rolling action of the cutter.The increase causes the weak nodes to break,and the crack begins to develop and expand.Then as the load continues to grow,the cracks gather and penetrate into the crushing zone,and the crushing zone is compacted with plastic deformation.The process consumes a lot of cutting work,the load continues to grow,and new cracks begin to be formed around it.The volume of the crushing zone becomes larger and larger,the surface rock mass becomes weaker,and the new crack can extend to the rock surface.The plastic deformation of the crushing zone is limited,a large number of cracks penetrate the rock surface,the crushing zone cannot continue to store energy,and the rock surface is peeled off.Due to the impact effect,the ODC cutter has a significantly better inhibition effect on the plastic section in the process of rock crushing than the pick cutter,greatly reducing the specific energy of cutting.