Study on Waveform and Frequency Spectrum Properties of Geological Radar for Middle Weathering Limestone Surrounding Rock

In order to more accurately and objectively to carry out the geological radar field detection for middle weathering limestone surrounding rock, based on Zhengfeng highway tunnel of Ganxian-Xingguo expressway in Jiangxi province, the geological radar with type of LTD-2000 was adopted to execute the field detection to get the original interpretation images. The original images were preprocessed by filtering, background removal and speed transformation to eliminate the interference signal. RADAN7.0 geological radar special analysis software was used to analyze the characteristics of the reflected signal, amplitude and frequency spectrum of the interpreted images. The results show that when the water content is greater than 36%, the strong reflection characteristics of the interpreted images are obvious, the average amplitude is greater than 0.65, the spectrum is dispersed and the main frequency is greater than 75MHz. When the water content is greater than 40%, the weak reflection characteristics of the interpreted images are obvious, and a large number of dense point-like reflection signals are visible. Besides, the maximum amplitude is less than 0.5 and the main frequency is less than 45MHz under this condition, so the low frequency characteristics are obvious. The study can provide certain reference for geological radar advanced detection in limestone surrounding rock.