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煤矿井下定向钻杆声波特性研究

Study on sound wave characteristics of directional drill rods in coal mines

  • 摘要: 声波传输技术具有信道稳定、传输速度快、不依赖其他传输介质等优点,是未来煤矿井下随钻测量技术的重要发展方向。基于连续钻柱波动方程,利用传递矩阵法对当前煤矿井下使用的不同结构定向钻杆声透射性能进行了研究:以不同钻杆长度L、接头长度2l+b、钻杆壁厚R0-r、接头壁厚R0-R1及钻杆级联数量N为参数构建频率响应特性计算参数矩阵,搭建钻柱声透射试验台进行验证,共分析了1 215种参数组合的钻柱频谱特性。研究结果表明:①组成周期性钻柱的单根钻杆长短对信号的通带影响较大,随着单根钻杆的长度增长,钻柱通带变窄,阻带变宽,钻柱通带周期变短;②随着接头长度的增长,计算周期内通带变窄,阻带变宽,影响钻柱信号传递;③直管段壁厚对钻柱信道的影响主要在于截面积的突变情况,随着直管段截面积与接头段截面积比值的增大,钻柱的透射系数波动减小,单一通带内透射系数更为平稳,此时更适合信号传输。

     

    Abstract: Acoustic transmission technology offers the advantages of a stable channel, high transmission speed, and independence from other media,making it a promising direction for future underground drilling measurement in coal mines. This study examines the acoustic transmission performance of various structural directional drill pipes used in underground coal mines by applying the transfer matrix method to the continuous drill string wave equation. Key parameters,including different drill pipe lengths (L),joint lengths (2l+b),drill pipe wall thicknesses (R0 -r),joint wall thicknesses (R0 -R1),and drill rod cascade numbers (N),were used to construct a frequency response characteristic calculation matrix. An acoustic transmission test bench was also built for verification. Analysis of 1, 215 parameter combinations of drill string frequency spectrum characteristics revealed the following findings:(1) The length of a single drill pipe significantly impacts the signal passband. As the pipe length increases,the passband narrows, the stopband widens, and the passband period shortens. (2) Longer joint lengths result in narrower passbands and wider stopbands,affecting signal transmission. (3) Changes in wall thickness affect the signal channel due to abrupt changes in cross-sectional area. An increased ratio of the cross-sectional area of the straight pipe section to that of the joint section reduces transmission coefficient fluctuations,stabilizing the transmission coefficient within a single passband and improving suitability for signal transmission.

     

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