| Coal mine underground personnel search and rescue serve as an important barrier to ensure mine safety and improve the survival rate of underground trapped personnel.It is of great significance for coal mine safety production to accelerate the updating of their technology and the research and development of equipment.Due to its unique characteristics,UWB radar wave life information recognition technology has been gradually applied and popularized in natural disasters such as ground fire rescue,earthquake,and avalanche.However,there are few reports on its application in the field of mine safety and rescue.The main reason is that the ultra-wideband radar wave penetrates the coal body for life information recognition process,which will cause the attenuation of the radar wave due to the characteristics of the coal medium.Studying the transmission attenuation variation rule is the basis of life information recognition,and it is also a difficult problem to be overcome in the recognition process.In order to study the attenuation change law and life information recognitioneffect of the ultra-wideband radar wave through the coal body,a life information detector based on the ultra-wideband radar wave was designed and verified on site.This paper intends to use theoretical analysis,laboratory experiments,and field tests to analyze the transmission attenuation of ultra-wideband radar waves in coals with different degrees of deterioration and thickness.The transmission attenuation factors are analyzed and sequenced.The life information identification principle verifies the effectiveness of personnel detection,and proposes the effective range of personnel detection under different conditions.The NS-187 mine radio frequency signal attenuation system was used to analyze the transmission attenuation law of the ultra-wideband radar signals about lignite,long flame coal and lean coal at 25cm,45cm,65cm and 85cm thickness.The results show that the transmission attenuation of radar waves is inversely related to the degree of deterioration of coal samples.The increase in coal thickness will increase the attenuation of radar wave transmission.The attenuation law at different detection frequencies indicates that during the radar wave transmission,the energy is concentrated near the center frequency of the antenna,and there will be multiple peaks as the thickness of the coal body increases.Combined with the ultra-wideband dielectric spectrum concept-80 test system,the influences of the dielectric constant,conductivity,and loss tangent of coal samples on transmission attenuation are analyzed,and their importance are ranked.The results show that the conductivity has the most influence,the influence of the dielectric constant is mainly concentrated around the peak,and the effect of the loss tangent on the transmission attenuation is negligible.Based on the ultra-wideband radar wave life information detection system,the detection distance and detection error of people were cross-analyzed in the field test,and the detection effects of three coal samples at different thicknesses were compared.The results show that the identification of life information in coal samples with low metamorphism is difficult,and the error of identification of life information in coal samples with high metamorphism is small and the effective range is large.Among the three coal sample detection effects,lignite has the shortest detection distance and the largest detection error;long flame coal is the second;lean thin coal has the best detection effect and the largest effective detection range,which is most conducive to the penetration detection of radar waves.The comprehensive comparison of the three coal samples shows that when the thickness of the coal body is greater than 3m,the overall personnel detection error is greater than lm.At this time,the detection data cannot provide reliable analysis,so it is not conducive to on-site personnel search and rescue. |
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