Experimental Study On Physical And Mechanical Characteristics Of Rock Under Ultrasonic Excitation

With the increasing workload of rock fragmentation,it is of great practical significance to further improve the rock breaking efficiency.At present,the common method of rock breaking,there are also large,low consumption breaking efficiency of rock material,ultrasonic wave has the advantages of good directivity,strong penetrating power,concentrated energy,has been widely used in various fields of the national economy.In this paper,ultrasonic is introduced into rock fragmentation,and the fracture mechanism of rock under ultrasonic excitation is explored by theoretical analysis and laboratory test,so as to provide reference for the efficient fragmentation of hard rock.The main achievements of this dissertation are as follows:(1)The ultrasonic circulation impacting rock and ultrasonic resonance rock breaking phenomenon,focuses on the rock crushing mechanism under ultrasonic excitation,the feasibility and superiority of ultrasonic excitation of rock breaking,determine the initial frequency,power and time as the key factors influencing the incentive effect of ultrasonic excitation of rock breaking.(2)A set of ultrasonic excitation rock testing system has been designed and developed,and the failure characteristics of rock specimens under different power and excitation time have been tested and compared by using this system.The results show that with the increase of ultrasonic power,the rock pressure on the basis of a certain test piece,the destruction effect significantly strengthened,ultrasonic power increased to about 3200 W,the standard sandstone specimens are rapidly destroyed.(3)The mechanical and strength variation characteristics of rock specimens under different excitation modes are explored.The microstructure characteristics of rock samples before and after ultrasonic excitation are compared and analyzed.Test shows:(1)the strength of rock specimen decreases with the increase of excitation time,and the relationship between them is approximately linear;(2)under different excitation modes,the strength of rock specimen decreases in a short time.When the energy diffuser is installed,the strength of rock specimen decreases by about 10% at about 40 s;(3)by microscopic scanning,it is found that after the ultrasonic excitation,many cracks are found in the core,the surface and the side of the rock sample,and the core is cut into different shapes with the shape of the quadrilateral.(4)By means of numerical simulation,the stress,strain and shearing stress characteristics of rock under the change of ultrasonic frequency and amplitude are systematically analyzed.The result shows:(1)when the frequency changes,the stress,strain and shearing stress inside the rock will reach the peak at a certain frequency,while the stress and strain change little at other frequencies;(2)when the amplitude changes,as the amplitude increases,the stress,strain and shearing stress inside the rock will also increase,and approximately linear relationship with the amplitude.