Study on the evolution law of micro damage and utilization efficiency of fracture energy in green sandstone under the action of ultrasonic vibration
The rock-breaking technology of ultrasonic vibration has significant advantage and development potential.In order to study the evolution law of micro damage and utilization efficiency of fracture energy in rock under the action of ultrasonic vibration,combined with physical experiment and microscopic parameter calibration,the relationship of macro and micro mechanical responses in green sandstone was established.The evolution laws of contact force field,failure characteristics and crack characteristics under the action of ultrasonic vibration were analyzed,and the utilization efficiency of fracture energy was studied.The results show that:(1)in the initial stage of excitation,the maximum contact force is concentrated in the upper end of the green sandstone,while the internal contact force is relatively small,showing an obvious"V"shape.With the increase of the excitation,the contact force continues to increase,and the original disorderly distribution of the contact force is gradually distributed in the regular distribution,transmitting to the lower end in the form of wave.(2)The failure process of green sandstone can be divided into the three stages of emergence,expansion,and penetration,and the final failure is characterized by unilateral shear failure.Under the same vibration frequency,with the increase of amplitude,the number of damaged blocks and cracks in green sandstone generally shows the upward sloping trend.Under the same amplitude,with the increase of vibration frequency,the number of damaged blocks and cracks in the green sandstone shows the up and down fluctuating trend.(3)The order of crack generation time is as follows:maximum value of shear crack(acoustic emission),maximum value of tensile crack(acoustic emission),equal cumulative crack(tensile and shear cracks).In the initial stage of ultrasonic vibration excitation,the green sandstone is dominated by shear cracks,and eventually by tensile cracks,and the tensile effect plays the major role in the failure process.During this process,the cracks mainly expand in the direction parallel to the ultrasonic vibration load,while cracks expand less in the horizontal direction.(4)Under the same vibration frequency,with the increase of amplitude,the utilization efficiency of fracture energy in green sandstone shows the decreasing and fluctuating trend.Under the same amplitude,with the increase of vibration frequency,the utilization efficiency of fracture energy in green sandstone shows the up and down fluctuating trend.The range of the utilization efficiency of fracture energy is 9.448％-12.456％.The research results not only preliminarily explore the damage evolution law and utilization efficiency of fracture energy in green sandstone under the action of ultrasonic vibration from the microscopic perspective,but also provide reference for the reasonable selection of parameters in the crushing process of rock.
rock mechanicsgreen sandstoneultrasonic vibrationparticle flow simulationdamage evolutioncrackfracture energy
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