Elastic constants of Solenhofen limestone and their dependence upon density and saturation

Abstract

An ultrasonic pulse technique at 3 Mc/s was used to determine the longitudinal (P) and shear (S) elastic wave velocities in 24 samples of Solenhofen limestone at atmospheric pressure and 25°C, with and without water saturation. The densities of the air-dried samples range from 2.48 to 2.66 g/cm3. Comparison of the results with the single crystal constants of calcite and with the high-pressure data of Hughes and Cross is made. The conclusions are: (1) Both P and S velocities in dry Solenhofen limestone are linear functions of the density at atmospheric pressure and 25°C. The velocity-density slopes for the dry samples are 5.11 and 1.625 km/sec per g/cm3 for the P and S velocities, respectively. (2) Inhomogeneity of Solenhofen limestone is slight, resulting in less than 3 per cent deviation in the P and S velocities from the least-squares curves. (3) Extrapolation of both the dry and the saturated P and S velocities to the limiting density (density of calcite) shows that, as the porosity decreases, the behavior of the limestone can be interpreted as an aggregate of randomly oriented single crystals of calcite. (4) Application of hydrostatic pressure to dry Solenhofen results in the same limiting P velocity as is obtained from the compressibility and density of the poly crystalline components at 1 atmosphere pressure. (5) Water saturation of the limestones decreases both the P and S velocities. The saturated velocities are linear functions of the saturated densities. There seems to be a small decrease in the matrix rigidity of the limestone with saturation.