Frequency spectrum characteristic of quartz sandstone rock mass with GPR

Ground penetrating radar(GPR) electromagnetic waves which penetrate through rock and soil mediums and are reflected back carry internal information about the target objects. The GPR basic frequency values of Fourier spectra can be used as a quantitative index of judgment for the structure characteristic of rock and soil mediums. Based on a highway tunnel project with the surrounding rock of quartz sandstone,advanced geological exploration test was carried out in front of the tunnel face with MALA GPR and a 100 MHz shielded antenna. Typical Class Ⅴ,Class Ⅳ and Class Ⅲ quartz sandstone surrounding rock mass were chosen to analyze their waveform graph information characteristic and the Fourier spectrum frequency characteristic during electromagnetic wave propagation in rock mass mediums. The regularity of GPR wave basic frequency values corresponding to the quartz sandstone rock mass medium in a certain sensitive frequency range due to its structure and surrounding environment changes was obtained through field test data analysis. A comparison between the research results and engineering excavation practices shows that it is feasible to invert the basic frequency value characteristic of GPR waves derived from advanced geological exploration for determining the structure characteristics of surrounding rock.