Abstract
This paper systematically examines the feasibility of using ultrasonic vibration excitation for rock breakage and fragmentation; it focuses on the failure mechanisms of rock mass under the impact of ultrasonic waves, and the development of ultrasonic technology. Laboratory testing using a self-designed system was conducted in this paper to further validate the efficiency and reliability of rock breakage using ultrasonics. The results show that: (i) under the effects of both the high speed impact of ultrasonic vibration excitation and induced rock vibration excitation, a fracture is initiated and propagates rapidly within and outside of the rock. Under ultrasonic vibration excitation for 140 s, the compressive strength decreased by 45.6%; (ii) under the excitation of ultrasonics, the rock specimens failed completely in a short time from inside to outside, and there are distinct fissures in the internal nucleation of the rock. It is suggested that ultrasonic excitation provides a novel and promising option for rock fragmentation and breakage, which optimises the efficiency of underground hard rock engineering.
Highlights
Rock breakage and fragmentation have played an increasing role in civil and mineral sectors, and one of the challenges is to improve the efficiency of rock fragmentation by reducing the material consumption [1]
The results revealed that ultrasonic excitation can effectively increase the porosity of samples and reduce rock strength, which proves the feasibility of the ultrasonic vibration excitation method in rock engineering
They used ultrasonic waves to conduct vibration excitation on coal samples, combined with nuclear magnetic resonance (NMR) observation technology and electron microscope scanning technology to understand the variation of pore sizes of coal samples against excitation time, and disclosed that ultrasonic high-frequency vibration can increase the porosity of coal samples
Summary
Rock breakage and fragmentation have played an increasing role in civil and mineral sectors, and one of the challenges is to improve the efficiency of rock fragmentation by reducing the material consumption [1]. The existing methods mainly include drilling and blasting, hydraulic fracturing, and thermal fracturing These methods normally have the disadvantages of the serious wear of drill pipes, slow borehole drilling speed, large loss of machine tools and energy consumption, high costs, and unsatisfactory working efficiency in field application, especially when they are adapted to optimise hard rock breakage and fragmentation. The results revealed that ultrasonic excitation can effectively increase the porosity of samples and reduce rock strength, which proves the feasibility of the ultrasonic vibration excitation method in rock engineering. Tang et al [14] carried out experimental studies on ultrasonic cracking to increase the permeability of coal seams They used ultrasonic waves to conduct vibration excitation on coal samples, combined with NMR observation technology and electron microscope scanning technology to understand the variation of pore sizes of coal samples against excitation time, and disclosed that ultrasonic high-frequency vibration can increase the porosity of coal samples. It is found through statistical analysis of the compressive strength of the rocks that ultrasonic vibration excitation can effectively reduce the compressive strength of rock samples
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