Study On The Effects Of TBM Cutter Profile And Wear On Rock Fragmentation

The disc cutters are located at the front end of the full-section tunnel boring machine(TBM),which contacts directly with the rock and plays an important role in rock breaking processes.The cross-section profile of disc cutter can change the contact state between cutter and rock,and then affect the rock damage behavior.On the other hand,rock has strong abrasion ability,the cutter is worn severely during contact with rock,which causes the cutter deformation until failure;when cutter is worn,the cross-section profile also be changed and affect the rock breaking.This means that selecting suitable cutter for different working conditions and rock strata is the key to ensure the high efficiency of TBM tunneling.Therefore,it is of great significance to study the influence of the cross-section profile of disc cutter and wear on the rock fragmentation,to guide cutter selection and guide the design of new cutter with high efficiency and low wear.In this thesis,the flat-tip cutter and circular-tip cutter are considered,a three-dimensional particle flow discrete element-finite difference hybrid model for rock cutting is established,and the reduced-scale rock cutting experiment is carried out.By analyzing the results of rock cutting,the influence of cutter profile and wear process on rock breaking are investigated.The main research contents of this thesis include the following parts:(1)Based on the wall-zone coupling method,a three-dimensional particle flow discrete element-finite difference hybrid model for rock cutting is established.The advantages and applicability of the model are proved with the cutter penetration test.In addition,the multi-function vibration test table is refit and the rock cutting experiment platform is built and optimized,which can realize the rotary cutting.(2)Combined with the different factors,the flat-tip cutter and circular-tip cutter are considered in the simulation.By analyzing the specific energy,rock fragment volume,cutting load,crack number,and other results,the correlation between cutter profile shape and rock breaking is investigated.At the same time,the reduced-scale rock cutting experiment is carried out to verify the correctness of the conclusions obtained from the simulation.The results show that the cutter profile has a significant influence on rock fragmentation,the specific energy of the circular-tip cutter is lower than that of the flat-tip cutter;the reason is that the influence of difference of cutting load on rock breaking is obviously greater than rock fragment volume,and the circular-tip cutter needs less force and less work.(3)Based on numerical simulation and abrasive wear removal mechanism,the wear depth of cutter is calculated by piecewise superposition calculation,and the wear process of flat cutter and circular cutter are better realized.At the same time,the evolution of rock breaking of cutter is studied based on the variation trend of rock fragment volume,cutting load,crack number,and other results.The results show that the contact stress distribution of the flat-tip cutter in the width direction is more uniform when the cutter interacts with hard rock,while the contact stress at the top of the circular-tip cutter is the largest,and lower in the sides.It is the reason why the profile shape of flat-tip cutter is unchanged in the wear process and the circular-tip cutter is gradually flattened.In addition,compared with the flat-tip cutter,the stability of rock breaking of circular-tip cutter is worse,and gradually evolves towards the flat-tip cutter.