Research On Rock Breaking Mechanism And Performance Of Tipped Hob For Raise Boring Machine

As an important equipment for wellbore construction,the raise boring machine is widely used in mine development,subway tunnels,urban pipe corridors,etc.The working principle is to apply the pulling force through the drill pipe of the raise boring machine to press the tipped hob into the rock.In the middle,the drill rod rotates to drive the cutter to crush the broken rock.Compared with the early application of a wide range of applications such as impact and cutting,the rolling rock crushing of the tipped hob is the most efficient and adaptable rock breaking method.Based on this,this paper studies the rock breaking mechanism and rock breaking performance of the tipped hob,analyzes the influence of tool parameters and engineering parameters on rock fragmentation,further improves the rock breaking efficiency of the tipped hob and reduces the wear of the tool.In this paper,theoretical deduction,numerical simulation,and experimental verification are combined to study the rock breaking mechanism of the insert and the rock breaking performance of the hob.Through the research on the structure and arrangement of the tipped hob,the mathematical model of the insert motion is established.According to the geometric relationship of the space,the equations of the motion of different hob inserts are derived,and the motion track of the insert is drawn.Based on the blade body parameters of the tipped hob,the rock-breaking mechanism of tooth profile,tooth pitch and tooth profile wear is studied.The results show that the wedge tooth is preferred from the energy point of view;the positive force peak of the ball tooth is the largest,but In the whole process of rock breaking,the total energy consumed is relatively small;when the geological environment is hard rock,it is more suitable to select the ball teeth or the bevel teeth;the tooth hobs with different tooth shapes have an optimal spacing.The hob can achieve the best rock breaking efficiency;the influence of the insert wear on the hob is mainly on the feed force,because the increase of the feed force work will indirectly increase the torque of the cutter head and the drill pipe.In view of the complexity of the geological environment,the mechanism of rock breaking in the presence of joints and confining pressure of rock is studied.The existence of joints directly affects the generation and expansion of cracks,which affects the crushing efficiency of rocks.Class,one is that the joint promotes the destruction of the rock to a certain extent,whether it is favorable from the number of cracks or the force of the insert;the other is that the joint blocks the expansion of the crack to a certain extent,and the joint of the joint will be blocked.Reduce the rock breaking efficiency of the hob;from the energy point of view,the confining pressure only prevents the intrusion of the intrusion into the rock to a certain extent,and the resistance of the confining pressure to the insert has an extreme value;the influence of the confining pressure on the rock breaking is mainly Reduced crack generation and expansion,reducing the amount of rock breaking in the tipped hob and reducing the efficiency of rock breaking.The linear rock-breaking model of the tipped hob was established,the numerical simulation of the effects of penetration depth and moving speed on the feed force,lateral force and positive force is carried out.The results show that the feed force is both as the penetration depth and the moving speed increase.Increasing the trend,especially with the increase of penetration depth,the feed force increases exponentially;As the penetration depth increases,the lateral force increases exponentially,and the change trend is consistent at different moving speeds;The lateral force shows a decreasing trend,which indicates that the increase of the moving speed can suppress the generation of the lateral force to a certain extent;The positive force of the hob increases exponentially with the increase of the penetration depth;the positive force varies with the moving speed.The increase is almost constant,which means that the moving speed does not affect the positive force of the hob;At different moving speeds,the peak-tovalley values of the feed force and positive force curves are basically the same,and the load fluctuations of the feed force and the positive force are rolled.The knife movement speed has nothing to do.Based on the influence of tooth profile on rock breaking performance,the numerical simulation study on the bearing capacity of four different toothed hobs of wedge tooth,pick tooth,conical tooth and spherical tooth was carried out.The results show that the positive force curve of the tipped hob is periodic.The change,the period does not change with the increase of the penetration depth,and does not change with the change of the tooth shape,which is caused by the arrangement rule of the inserts on the tipped hob;With the increase of penetration depth,the feed force,lateral force and positive force of the hobs of different tooth shapes increase exponentially,and the spherical tooth change most obviously with the increase of penetration depth.It is known from the fluctuation amplitude of force.The fluctuation relationship of the force of the hob in each direction is positive foece>feed force>lateral force,and the fluctuation relationship of the force in each direction is analyzed from the tooth shape: spherical tooth>conical tooth>pick tooth>wedge tooth.The mathematical model of slip is established,and the equation solution of the insert hob with minimum friction is derived.It is pointed out that the pure rolling point of the tipped hob will change with the geometric parameters of the tool.The position of pure rolling is near the center of the hob.It is biased towards the big end side.Further deducing the trajectory of the hob after the cone is unfolded according to the taper surface,and on the basis of this,the formula of the single tooth displacement and the total amount of slip around the drill pipe is derived,and the relevant formula of the slip amount is analyzed.The parameters affecting the slip amount are found in the installation position,cone inclination angle,vertebral body radius,penetration depth and number of teeth,and the influence of these parameters on the slip is analyzed in turn.The test verification of the slip was carried out.By studying the rolling trajectory of the tipped hob on the rock and concrete,the way of the forward slip,non-slip and backward slip of the hob was verified.The insert with the smallest diameter has the largest amount of insert slip,and the position of the pure rolling point is near the main cone 3,which proves that the model derivation about slip is correct.Through the engineering test of the raise boring machine,the experimental research on the influence of the rotation speed of the cutterhead on the tension and torque of the drill pipe was carried out.The results show that the tensile force of the drill pipe does not change with the increase of the rotational speed,the tensile force of the drill pipe and the pressure of the thrust cylinder have a proportional relationship;As the rotational speed increases,the torque of the drill pipe remains basically the same;The experimental study on the influence of pulling force and rotating speed on the drilling speed shows that the drilling speed of the drill pipe increases rapidly with the increase of the pulling force,and the curve of the pulling force and the drilling speed is exponential;with the increase of the rotating speed,the drilling of the drill pipe The speed increases steadily,and the relationship between the rotational speed and the drilling speed is linear.The experimental results of the effects of tension and speed on the energy consumption of rock breaking indicate that the best working parameters are 1483 kN tensile force(set thrust cylinder pressure is 11 MPa)and the rotational speed is 4 r/min;The method of parameters not only provides a reference for how to select engineering parameters in the new geological environment,but also lays a foundation for further research on the rock breaking performance and the design of the cutterhead.The paper has 153 figures,10 tables,and 161 references.