Research on the Resonance Characteristics of Rock under Harmonic Excitation

Li, Siqi; Tian, Shenglei; Li, Wei; Yan, Tie; Bi, Fuqing

doi:10.1155/2019/6326510

“…In the literature [47][48][49][50][51][52][53][54][55][56][57][58], it is proposed to use measures to alleviate rockburst intensity, such as large-diameter drilling to increase fractures and water injection to rock (coal) seams.…”

Section: Discussion Of (Dm/dt)mentioning

confidence: 99%

Rockburst Occurrence Mechanism Based on the Self-Sustaining Time-Varying Structure of Surrounding Rock

Fan

¹

,

Zhao

²

,

Wang

³

et al. 2020

Shock and Vibration

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Rockburst is one of the major disasters that threaten the safety of personnel and equipment underground and affect the normal production of the system. At present, there are many kinds of research on rockburst occurrence mechanisms, but most of them are based on statics and do not consider the time-varying effect of surrounding rock state. Regarding the stress state and characteristics changing with time of the surrounding rock support structure and the internal parameters after the tunnel excavation is analyzed qualitatively in this paper, the concept of the “self-sustaining time-varying structure of the surrounding rock” is put forward. The “self-sustaining time-varying structure of the surrounding rock” is regarded as a nonperiodic time-varying system with a single degree of freedom, then its dynamic characteristics are analyzed by using the momentum theorem of the particle system. The results show that when the mass of the self-sustaining time-varying structure changes with time and d m / d t < 0 , the rockburst may be induced by the free vibration with increasing amplitude. The faster the d m / d t changes, the more violent the rockburst is. This explains the rockburst occurrence mechanism from a new angle and explains the phenomenon that most rockburst occurs when σ θ was lower than σ c better.

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“…The vibration excitation of the testing machine comes from similar materials; the vibration excitation of similar materials comes from the vibration of the testing machine and the instantaneous release of energy when the gas burst occurred. Data show that the natural vibration frequency of relatively complete rock is above 1000 Hz [28]. The test results show that the natural frequency of similar materials is 2170 Hz.…”

Section: Analysis Of Testing Machine Parametersmentioning

confidence: 92%

Experimental Accuracy and Stability of Gas Outburst Experimental System

Liu

¹

,

Sun

²

,

Wang

³

et al. 2021

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Gas outburst is an important issue in deep coal mining. At present, the gas-rock coupling change mechanism and intensity prediction of gas outburst are not clear. The research of gas outburst simulation experiment is particularly important. The State Key Laboratory of Gas Disaster Monitoring and Emergency Technology of China independently developed a large-scale coal and gas outburst physical simulation test system. However, the influence of the design parameters of the testing machine on the stability and accuracy of the simulation experiment is unclear. The article analyzes the energy conversion in the process of gas outburst through experimental simulation phenomena and results. The experimental simulation results show that the energy released by the CO2 gas in similar materials is the most important energy source. The cracks of similar materials increase the nominal volume of similar materials, and the deformation energy stored in similar materials slightly increases. The experimental simulation results are consistent with the actual situation on site. Combined with CAE simulation analysis, the displacement and pressure of the indenter of the experimental machine remained basically unchanged during the experiment, and the system did not produce resonance. Comprehensive analysis shows that the design of the test machine meets the simulation requirements.

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“…x 0 + ξω n x 0 Þ; B is the amplitude, m/s 2 ; ξ is damping ratio, dimensionless; ω d is the natural frequency of coal, Hz; φ is the phase angle, rad. Assuming that coal is an elastic medium, then its stiffness can be obtained from the stiffness equation of 2 Geofluids elastic material [28,29]:…”

Section: Models Of Natural Frequency Of Coalmentioning

confidence: 99%

Natural Frequency of Coal: Mathematical Model, Test, and Analysis on Influencing Factors

Wei

¹

,

Zhang

²

,

Wen

³

et al. 2022

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The difficulty in enhancing the low permeability of deep coal seams is the key problem restricting gas extraction. The technology of coal rock resonance and permeability enhancement excited by vibration wave is hailed as a new technology to enhance coal seam permeability. In particular, the effect of resonance and permeability enhancement is remarkable when the excitation frequency is exactly the same as the natural frequency of coal. In order to promote the application of the technology, the first step is to explore the variation characteristics of coal natural frequency and its influencing factors. In this study, two mathematical models of coal natural frequency were established, and the variations and influencing factors of coal natural frequency were discussed through an experiment on the natural frequency of coal. The results show that coal vibration has multiorder natural frequency which grows with the increase of the order. In addition, the natural frequency of coal is closely related to its elastic modulus, density, size, mass, stiffness, and other physical and mechanical parameters. The larger the coal size and mass are, the lower the natural frequency would be. The natural frequency parallel to the bedding plane is higher than that perpendicular to the bedding plane. For the saturated coal sample, moisture changes its density and reduces its elastic modulus. Consequently, its natural frequency is lower than that of the dried coal sample. The difference of organic matter and mineral content coal of different rank affects the physical and mechanical properties of coal, which leads to the difference in natural frequency of different-rank coals. The natural frequencies of different-rank coal show bituminous > anthracite > lignite. The natural frequencies of coal samples under different influencing factors are all tens of Hz. Thus, the vibration excitation of coal under the low-frequency condition is the focus of future research. The study can provide a theoretical basis for the technology of coal resonance and permeability enhancement excited by vibration wave.

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Research on the Resonance Characteristics of Rock under Harmonic Excitation

Cited by 14 publications

References 16 publications

Rockburst Occurrence Mechanism Based on the Self-Sustaining Time-Varying Structure of Surrounding Rock

Rockburst Occurrence Mechanism Based on the Self-Sustaining Time-Varying Structure of Surrounding Rock

Experimental Accuracy and Stability of Gas Outburst Experimental System

Natural Frequency of Coal: Mathematical Model, Test, and Analysis on Influencing Factors

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