Research On Longitudinal Vibration Of Raise-boring Tools Under Reaming Conditions

In the raise drilling engineering,the rock was broken by the hob rolling.The essence of rolling breaking are leaping invasions of rocks by hob cutter teeth,which accompaniy a large amount of impact loads.With the rotating of reamer,impact loads are periodically generated,causing the longitudinal vibration of the reaming tool system.Under reaming conditions,the reaming tool system,consisting of ordinary pipes,stabilizing pipes and a reamer,is subjected to large loads and compound force.The longitudinal resonance will be induced when the longitudinal natural frequency coincides with the vibration frequency,leading to fatigue and damage of drilling tools.In this paper,starting from the natural and vibration frequencies,the longitudinal vibration of the reaming tool system under reaming conditions is systematically discussed through theoretical analysis,numerical simulation,programming calculations and field experiments,etc.First,aiming at the longitudinal natural frequency,a longitudinal free-vibration mechanical model suitable for reaming tool systems was established,and the analytical formula of longitudinal natural frequency was deduced.In the case of four different diameter reamers,three different types of drill pipe,four different materials and four different reaming tool length conditions,the finite element model of the reaming tool system was established,and the calculation of different parameters was performed.The longitudinal natural frequency table was established within100 meters of the reaming tool length.The study shows that the change in the length of the reaming tool is the main reason affecting the natural frequency,and the length is negatively correlated with the longitudinal natural frequency of each order.Secondly,aiming at the longitudinal vibration frequency,a mathematical model of the rock breaking frequency was established,and the analytical formula of vertical vibration frequency under reaming conditions was deduced.Under the conditions of two different types of reamer,three different rows of hob teeth,and three different angles of edge hob arbor,the vertical vibration frequency of reaming tool systems was orthogonally calculated,and the vertical vibration frequency table was established.The study shows that the diameter of reamers and the number of rows of hob teeth are the important factors affecting the longitudinal vibration frequency of reaming tool systems,and the two are positively related to the longitudinal vibration frequency.Thirdly,aiming at the longitudinal resonance problem,the relevant inducing factors were discussed,and a fuzzy control algorithm for reaming rotating speed,based on fuzzy control theory,was designed.The study shows that for reamers with diameters in the range of 1.75 m to 3.5m,the smaller the reamer diameter and the shorter the reaming tool length,the greater the risk of longitudinal resonance.The fuzzy control algorithm can realize the dynamic adjustment of the rotating speed and effectively avoid resonance.Fourthly,aiming at the problem of vibration measurement under reaming conditions,an indirect measurement method of longitudinal vibration frequency based on acoustic signals is proposed.Relying on No.2 ventilation shaft project of the Jiyi railway tunnel,the longitudinal vibration frequency of the reaming tool system was measured on-site under the conditions of 2.25 m reaming diameter,surrounding sandstone with 120 Mpa uniaxial compressive strength,flat-bottomed reamer,6-rows toothed hob,and edge hob arbor angle of 53°.The experimental results show that the scheme of indirect measurement of the longitudinal vibration frequency of the drilling tool using acoustic signals is feasible,and the measurement accuracy can meet the engineering needs.This study had obtained the longitudinal vibration law of the reaming tool,the fuzzy control algorithm to avoid the resonance speed,and the indirect measurement of the longitudinal vibration frequency of the reaming tool system.These results have a strong application value in practical construction projects.