基于层理和煤阶影响的煤体固有频率特征研究

Study on natural frequency characteristics of coal based on the influence of bedding and coal rank

为探明振动波激励煤体共振增渗技术的优势频率,采用自主搭建的煤体固有频率测试试验系统,依据敲击法测试原理对高、中、低3种不同煤阶的正方体干燥煤样进行三维面固有频率测试和分析。结果表明:汉宁窗较适合煤体振动信号FFT分析,可以准确识别频谱峰值所对应的频率,从而直接得出煤体的固有频率;力锤敲击力度只影响振动信号加速度幅值大小,对煤体固有频率变化无影响;同一煤样平行于层理面的固有频率大于垂直于层理面的,且垂直于层理两个面的固有频率略有差异;受煤基质、矿物质含量等因素影响,高、中、低3种不同煤阶煤样的力学性质不同,这是造成不同煤阶煤体固有频率差异性的主要原因。研究结果可为振动波激励煤体共振增渗技术应用提供理论依据。

In order to exploring the dominant frequency for the permeability enhancement technology of coal resonance excited by vibration wave,with the aid of an independently built coal natural frequency test system,the three-dimensional natural frequencies of different-rank(high,medium and low)dried cubic coal samples were tested and analyzed according to the test principle of the hammering method. The results showed that the Hanning window was suitable for fast Fourier transform analysis on vibration signals,as it could accurately identify the frequency corresponding to the spectral peak and thus directly obtained the natural frequency of coal. The hammering force only affected the acceleration amplitude of vibration signals,barely affecting the natural frequency of coal. For the same coal sample,the natural frequency of the plane parallel to bedding was larger than that perpendicular to bedding,and the natural frequencies of two planes perpendicular to bedding were slightly different. Influenced by factors such as coal matrix and mineral content,different-rank coal samples were endowed with varying mechanical properties,which was the main reason for the differences in their natural frequencies. The research results were expected to provide theoretical basis for the application of the permeability enhancement technology of coal resonance excited by vibration wave.