| With the continuous development of China’s economy and the continuous improvement of comprehensive national strength,tunnels and underground engineering have achieved unprecedented rapid development.The current tunnel construction methods include drill-and-blast method,TBM(Tunnel Boring Machine)method and partial-section roadheader method.The section size of drilling and blasting construction is not controlled,and the safety benefit is poor;the TBM is only suitable for long-distance circular section tunnels,and the cost is large.The partial-section roadheader method is a tunnel construction method using boom-type roadheader developed in recent years.Compared with coal mine tunneling,the tunnel construction section is larger,and the rock layers is complicate.The existing mining boom-type roadheader cannot adapt to tunnel construction.requirements.Aiming at the problems of large cutting section in tunnel construction,severe vibration of cutting mechanism during tunneling and insufficient dynamic stability of the whole machine,this study establishs the design theory of cutting mechanism of boom-type hard rock tunneling roadheader,in order to improve the adaptability,reliability and technological advancement of the tunneling machine,so as to meet the increasingly wide range of tunneling construction machine needs.The main research contents and conclusions are as follows:(1)Starting from the functional requirements of the boom-type hard rock tunneling roadheader,the configuration relationship between the main functional components and the drive system was sorted out.Based on the working range of roadheader and the requirements of cutting and loading capacity,the main structure layout and parameter design of roadheader are carried out,and the basic dimensions and working parameters of hard rock tunneling roadheader are obtained.The stability of the roadheader during cutting operations at the extreme position within the working range of the cutting mechanism have been checked.The results show that the main structure layout and basic design parameters of the boom-type hard rock tunneling roadheader are reasonable,which provides basic parameters for the subsequent dynamic characteristic analysis.(2)The structural characteristics of the cutting head of hard rock roadheader were studied,the influence of the cutting line spacing,helix angle,cutting rock breaking angle and deflection angle of the cutting head on the cutting performance was analyzed,and an evaluation index system for hard rock cutting performance was constructed.Aiming at the multi factor and multi-objective optimization design of hard rock cutting head,through the orthogonal numerical simulation and feature extraction of single pick cutting and overall multi pick s cutting operation,the comprehensive influence mechanism of pick arrangement parameters and installation parameters on the cutting performance of hard rock roadheader is revealed.The internal relationship between the geometric parameters of hard rock cutting head,cutting operation parameters and cutting capacity and performance was studied and analyzed,and the design and optimization method of hard rock roadheader cutting head was established.(3)The external excitation of the random load of the cutting head and the internal excitation of the system in the working process of the cutting mechanism system were comprehensively analyzed,and the dynamic model of the cutting mechanism system was established.Aiming at the strong time-varying load of hard rock roadheader in large section tunnel,assuming that the cutting resistance and traction resistance of the pick obey theχ~2 distribution,and the lateral force obeys the normal distribution,and considering the correlation between the two,the random load model of cutting head was established by using the theory of random process,the hard rock roadheader three-direction random load are simulated by using random process and other theories,and the power spectrum of the cutting head are analyzed,the frequency characteristics of cutting head under random load are obtained.The effects of various dynamic excitations such as time-varying stiffness of cutting spindle support bearing,time-varying stiffness of gear meshing and comprehensive meshing error of gear on the cutting mechanism system of hard rock roadheader were comprehensively considered.On this basis,the dynamic model of torsional vibration of two-stage planetary reducer and bending torsional coupling of rotor system of cutting mechanism was established by using Lagrange equation,and the multi degree of freedom variable parameter nonlinear dynamic differential equations were derived,which lays a foundation for the study of nonlinear dynamic characteristics of hard rock tunneling roadheader cutting mechanism system.(4)Using the Newmark-βnumerical method,the nonlinear dynamic differential equations of the system are solved,and the time domain and frequency domain responses of the cutting mechanism planetary reducer and cutting head rotor system under different rock hardness are studied.The results show that the variation trend of system vibration under random load is similar to that of external load,the system is in a chaotic state,and the response frequency components are diversiform and complex.In addition to the fundamental frequency and octave frequency of meshing frequency,the dominant frequency of planetary transmission at all levels also has low-frequency and side frequency components caused by random load excitation.For the rotor system,it is mainly low-frequency vibration caused by random load.The dynamic analysis results of the cutting mechanism system provide a theoretical basis for the vibration reduction and dynamic design of the roadheader.(5)The dynamic stability model of boom-type hard rock tunneling roadheader under random load was established,and its dynamic stability under uphill and horizontal driving conditions is analyzed.When the cutting mechanism cuts laterally at three limit positions,the influence laws of parameters such as elevation angle,swing angle and structural size of the cutting mechanism on the dynamic stability of the roadheader were obtained,it provides a basis for the dynamic stability design and parameter optimization of large section hard rock roadheader.(6)Vibration test and analysis were carried out on the prototype.The vibration test system of hard rock tunneling roadheader was constructed,and the dynamic performance test plan of roadheader was formulated.The vibration signals of the roadheader under different working conditions such as no-load and lateral cutting were measured respectively,and the dynamic response results under various working conditions were compared and analyzed,the influence law of random load on the vibration response of roadheader cutting mechanism is obtained.Combined with the field application case of hard rock tunneling roadheader,the correctness of the dynamic theoretical model and design method of hard rock tunneling roadheader cutting mechanism established in this thesis has been verified,which provides an experimental basis for the dynamic design of boom-type hard rock tunneling roadheader cutting mechanism. |
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