Construction And Numerical Analysis Of Rock-breaking Mechanical Model Of TBM Hob Based On Passivation Effect Optimization

Cutterhead is the core functional component of TBM,and its performance directly determines the rock breaking efficiency and construction speed.Therefore,in order to further improve the rock breaking effect,it is necessary to further explore the cutting performance and rock breaking mechanism of hob in the process of cutting rock.Aiming at the shortcomings of the current rock breaking force formula,this paper puts forward the optimized rock breaking force calculation model and formula,and analyzes the influence of the change of parameters in rock breaking by hob on the rock breaking efficiency combined with the discrete element software PFC^3D.It mainly includes:(1)By studying the CSM prediction model and the new tool tip simplified model,it is found that there are still deficiencies:the former does not consider the passivation effect of the hob cutting rock tool head,and the simplified model of the latter oversimplifies the tool head for the convenience of calculation,which makes the contact area between the hob and the rock much larger than the actual situation,that is,the influence of the tool head passivation effect makes the calculation result too large.Although the above method solves the complex calculation problem of rock breaking force in the process of rock breaking to a certain extent,there is still an error between the calculated rock breaking force and the actual measured value that can not be ignored.In order to further improve the calculation accuracy,this paper continues to optimize the simplified model,and puts forward the rock breaking force prediction model and formula based on the optimization of passivation effect.The calculation model can better predict the normal rock breaking force,the maximum error is within15%,and the average error is controlled within 5.58%.(2)The numerical analysis results of linear cutting rock breaking show that the normal rock breaking force and rolling rock breaking force increase with the increase of penetration depth,knife spacing and confining pressure;When the cutting depth is6mm and the penetration is 98.3mm,the specific energy reaches the lowest value,which is the best combination of penetration and knife spacing.At this time,S/P=16.38.(3)The normal rock breaking force of linear cutting is slightly higher than that of rotary cutting.On the contrary,the rolling rock breaking force of linear cutting is slightly smaller than that of rotary cutting.The difference of rock breaking force between linear cutting and rotary cutting is small,and has the same change trend with the change of dependent variables.Therefore,using linear cutting to explore rock breaking by hob is an efficient and reliable method.(4)Combined with the numerical simulation data of the two cutting methods and based on the entropy weight method,the three rock breaking efficiency parameters are comprehensively evaluated.The results show that the knife spacing and penetration are severe sensitive indicators,and the confining pressure is mild sensitive indicators.The order of sensitivity is penetration>knife spacing>confining pressure.The research results of this paper have certain theoretical and guiding significance for exploring the change of rock breaking force,the law of crack development of rock and guiding the actual construction.