Rock mass evaluation using in-situ velocity and attenuation measurements

摘要

The purpose of this work was to implement a method to determine in situ, the degree of fracturing and weathering of granite rock massifs, beneath a sedimentary cover. using refraction data for P-wave velocities determination and attenuation measurements, obtained from a radial set of seismic lines in each place, rock mass assessment was achieved. Attenuation measurements were obtained from seismic attenuation spectra (Young and Hill, 1979; 1982; 1986) and by determination of the Q factor using the spectral ratio method (Bath, 1974). A quality index of the rock was built from direct observation of the fracture system and weathering degree and other parameters. A multivariate statistical analysis of the data was carried out. Preliminary results show that the method can be applied with success to granite mass evaluation, specially if we eliminate the effect of the sedimentary cover.