Physical properties of alpine rocks : a laboratory investigation
In this study, basic physical properties of rocks from the Swiss Alps have been determined and analyzed in an integrated manner. Laboratory measurements have been carried out on the following physical parameters: bulk density, matrix density, thermal conductivity, magnetic susceptibility and P-wave velocity. Several other parameters have been deduced by calculation, such as porosity, and the anisotropies of the thermal conductivity and P-wave velocity, and finally seismic velocity attenuation.
... hermal conductivity has been measured at room temperature using a QTM (Quick Thermal Meter) apparatus. By analyzing the difference in thermal conductivity and its anisotropy under dry and saturated states, the pore configuration of most of the measured rock samples is shown to correspond to an inter-connected pore model and with the pores orientated in an aligned flat shape. Seismic P-wave velocity has been measured at room temperature under high confining pressures up to 400 MPa in steps of 20 MPa. P-wave velocity variation with pressure can be fitted to a semi-empirical relationship with 4 parameters in order to extrapolate the experimental data to higher pressure. The spectral ratio (SR) method has been used to obtain seismic wave attenuation as defined by the quality factor Q. The relationship between the different physical properties measured has been investigated using correlation coefficients and factor analysis for the various petrophysical parameters. From the correlation coefficients of the measured data, the best relationship is between Pwave velocity and bulk density, whilst the thermal conductivity and P-wave velocity seem not numerically correlated. Results from factor analysis confirm that the original 10 measured "parameters" are reduced to 3 independent factors. Although petrophysical parameters measured in the laboratory on surface rock samples are not the same at those under different conditions in the deep crust, the quantitative order of magnitude is definitely of great use for a better interpretation of geophysical survey data in different geological backgrounds. The laboratory study provides a better understanding of the variation of petrophysical properties with depth and other physical conditions.