: Reliable methods for estimating rock properties from empirical data are of great importance for the design of safe structures in rock, because in many cases only static or dynamic values of Young ’s modulus are available. Five exploratory drill cores near the ERAM radioactive waste repository at Morsleben, Germany, provide laboratory as well as in situ data of density, velocities of P- and S-waves, static Young ’s modulus, Poisson ’s ratio and RQD values for different strata. We investigate the dependence between static and dynamic Young ’s modulus. We conclude from our data as well as from data in the literature, that using an empirical parameter characterizing the quality of the rock mass will allow to estimate static Young ’s modulus from dynamic data or vice versa. In intact rock such as rock salt or limestone, the value of the quality parameter is lowest and about 1.1 GPa. The intact siltstone and claystone of the ERAM site with RQD = 1 yields quality values of about 7 GPa. In jointed siltstone and claystones (with average RQD values of about 0.4), values go up until 18 GPa. We find a week correlation between average RQD values and the quality parameter. The difference between the quality parameters of different types of intact rock has to be investigated further, e. g. by researching the hysteretic properties and their correlation with the quality parameter.
1 INTRODUCTION
In many cases, either static (i.e. static Young ’s modulus and Poisson ’s ratio) or dynamic (such as density, P-wave velocity) parameter values are known for rock. Estimates of the unknown parameter values need to be based on empirical and theoretical foundations. There are numerous publications dealing with this problem empirically, i.e., measuring the ratio of dynamic and static Young ’s moduli or collecting data of the ratio (e.g. Link 1968, Eissa & Kazi 1988, Bastos et al. 1998, Starzec 1999; a review by Haupt & Hermann 1987). Looking for the source of the differences between the two moduli, Cheng & Johnston (1981) focus on the role of microcrack density, while Starzec (1999) looks for the reflection of fracture porosity in macroscopic variables like the ratio of P- and S-wave velocity or the increase of density with P-wave velocity.
