Study On Rock Breaking Mechanism Coupled With Ultrasound Excitation And Mechanical Impact Control

The existing practice of hard rock fragmentation has proved that the single method of rock fragmentation can not fully meet the requirements of high efficiency,energy saving and green production in mines.Combining two or more rock-breaking methods to reduce the difficulty of rock cutting,improve the installed power of rock-breaking machinery and effectively improve the comprehensive efficiency of rock-breaking is an important development direction in the field of rock-breaking research in the future.In order to overcome the shortcomings of traditional mechanical impact rock-breaking drilling,such as low drilling strength,slow hole-forming speed,large loss of tools and materials,considering the advantages of strong ultrasonic penetration ability and concentrated energy,two rock-breaking methods are explored to be combined in rock-breaking.The response characteristics of rock under the combined action of ultrasonic excitation and mechanical impact are studied by theoretical analysis and numerical simulation.Systematic analysis has been carried out.The main results are as follows:(1)Using single-degree-of-freedom mechanical model,rock is treated as an ideal viscoelastic body.Combining with the impact-rock impact loading mechanical model,the failure characteristics of rock under ultrasonic excitation,the failure characteristics of rock under mechanical impact and its influencing factors are analyzed,and the response amplitude,excitation frequency and vibration of simple harmonic vibration of internal particle of rock under ultrasonic excitation are clarified.The relationship among amplitude,equivalent resistance and natural frequency of rock is that the response amplitude reaches its maximum when the excitation frequency is equal to the natural frequency of rock,increases with the increase of excitation amplitude and decreases with the increase of equivalent resistance.The more easily the rock is destroyed.(2)The dynamic model of rock under the combined action of ultrasonic excitation and shock is established,and the dynamic characteristics of the rock system of "ultrasonic excitation-mechanical impact" are analyzed.The characteristics of velocity attenuation in the form of power function in the process of particle collision in rock under combined action are clarified.It is considered that the obtained velocity is related to the frequency of ultrasonic excitation,the frequency of impact load,the amplitude of ultrasonic excitation stress and the stress amplitude of impact load.The displacement expression of rock under impact in resonance state is obtained,and the displacement of particle in rock is grasped with impact.Characteristic of load variation.(3)The dynamic response characteristics of rock under the combined action of ultrasonic excitation and impact are simulated and analyzed.The impact rate under the combined action of ultrasonic excitation influences the development characteristics of rock fissures.The vibration characteristics of rock particles under the impact load under the ultrasonic excitation are mastered.The failure mechanism of rock under the combined action is revealed,and the rock under the resonant state is impacted.The displacement of particle in stone is more than 40% higher than that under simple impact.