Rock Breaking Mechanism And Wear Of TBM Hob In Inclined Shaft

The two key issues in long distance and deep buried inclined shaft TBM driving are rock breaking efficiency and cutter wear.Therefore,to study the influence factors of rock breaking force,rock breaking efficiency,cutter design and cutter wear prediction in the process of TBM cutter breaking rock have both theoretical and practical significance.Based on TBM engineering in Shendong mining area and Shenhua Taigemiao mining area,the theoretical analysis,discrete element numerical simulation,similarity model test,abrasion test and field test methods are used in this thesis.The thesis aim at studying rock breaking mechanism,rock breaking efficiency factors,cutter design and cutter wear during the process of TBM excavation.The main research are as follows:1.The mechanical model of normal cutting force of arc blade wedged hob is established.The normal cutting force mechanical model is established based on the theory of rock extrusion and shear failure,and has been verified by field monitoring results.The influence of the radius of arc and the angle of the blade on the normal cutting force are also been obtained.The rock breaking normal force increases as the increasing contact area between the hob and the rock crushing failure area,and the increasing radius of arc.The cutting blade angle of the hob is the key parameter to the rock shear flailure.Only squeezing effect occurs if the blade angle is set too large and thrust of the hob strongly changes.Therefore,it is important to set a reasonable blade angle in order to increase the shearing effect.The mechanical model and analysis of parameters of the hob provide a reference for the design of the cutter.2.The optimal cutter spacing and the optimum penetration depth are obtained for the rock breaking efficiency of the arc blade wedged hob.Based on Shenhua Taigemiao mine,the discrete element numerical simulation of PFC is used to study the influence of the penetration and hob spacing in the hob breaking rock process to crack propagation,the energy consumption ratio is used as the index to get the optimal rock breaking parameters.According to the rock characteristics of the Shenhua mining area,the maximum rock breaking efficiency could be obtained when the optimal cutter spacing is 100 mm and penetration depth is 10 mm.It can provide reference for the application of cutters.3.The TBM rock breaking model test bed is set up.Based on city underground engineering laboratory test system of China University of Mining and Technology(Beijing),TBM rock breaking test system with variable cutter spacing and rotating hob is developed.The designed disc cutter is installed on the shield head,by adding a force-torque sensor,rock breaking is conducted through the rotation of the hob and Cutterhead.Based on the system,the influence of different penetration depth,hob spacing and blade type on rock breaking efficiency of TBM cutter is studied.Rock breaking test with different hob spacing is conducted.When the hob spacing is 15 mm,maximize rock breaking volume,reasonable broken blocks,the lowest energy consumption can be obtained.Rock breaking tests with the three blade hob type: the sharpe blade,arc blade,tooth blade wedged hob are conducted.The results show that: the sharpe blade hob test gets the highest rock breaking ratio and the lowest energy consumption,but the sharpe blade hob is the most easisly to wear.The rock breaking ratio of tooth blade wedged hob is higher than that of arc blade hob,the energy consumption is lower than that of arc blade hob,the rock breaking efficiency is higher than that of arc blade hob,it can provide a reference for the design of the practical construction.4.A new accurately method to measuring the volume of broken rock is proposed,the rationality of the hob spacing is evaluated by proposing the concept of rock breaking rate.Based on ultra high speed line laser 3D measurement system,a new accurately method to measure the volume of broken rock is established.By proposing the concept of rock breaking rate,it is the percentage of 3D scanning measured value of broken rock volume accounting for theoretical estimation value.The rock breaking rate is used to adjust the optimal hob spacing,when the hob spacing is too large,the percentage is lower than 50%.When the hob spacing is too small,the percentage is 50%~70%.When the optimal cutter spacing is obtained,the percentage is close to 100%,and the rock breaking volume reaches the ideal maximum value.5.The mechanism of cutter wear accelerated when an angle exists between the driving direction and rock tendency is clarifiedRock composition analysis,abrasion test are conducted by choosing surrounding rock in different depth of TBM excavation section for Shendong Bulianta coal mine area,and the cutter wear in situ are analyzed.The results show that: equivalent quartz content has the strongest correlation with CAI in Shendong Bulianta area,CAI increases with the increasing equivalent quartz content.When the needles cross the siltstone,medium sandstone and layered fine sandstone,it show three different failure modes: fine particle abrasion,coarse particle abrasion,tilt abrasion respectively.Layered fine sandstone has the most obvious crack propagation.When the CAI value increases,the scratch depth decrease,the needle abrasion increases,and the cutter wear increases.The cutter wear form is consistent with the needle wear form.Needles across layered sandstone prone inclined grinding,and cutter wear speed increase faster across layered sandstone,when there is an angle between driving direction and rock tendency,tilt abrasion is easily occurred to accelerate tool wear.6.The new type of hob is developed,which is successfully applied to the inclined shaft TBM project,and the problem of poor wear resistance of cutters is solved.Based on the analysis of abrasion and tunneling parameters of the hob,the reference standard of changing cutters is given.Based on the theoretical analysis and experimental results,a new type of hob is developed to be applied in field project.The cutter wear and tunneling parameters of TBM are analysed.The results show that: in the same geological conditions,the wear resistance ability of new hob is 20% more than that of usual tool,it can reduce the number of hob change,as well as improve efficiency.The total wear amount of hob on the edge is larger than that of the front hob,the wear degree of the cutter is related to its cutting speed and the abrasion resistance of the rock.When the difference between calculation speed and actual speed excess 18mm/min,the cutter is considered to be severely worn out,it’s time to open cabin to chang it.The development and application of new cutter and wear prediction successfully solve the cutter wear and frequent replacement problems during the inclined TBM excavation.It provides technical support,saves the maximum driving period and construction cost.