Scale effects in the determination of mechanical properties of joints and rock masses

Abstract

Rock masses are essentially inhomogeneous and discontinuous media. Hence, the results of lhe laboratory and in situ tests for the determination of its mechanical properties show a dependency on the specimen size which is called scale effect.

The Scale Effect concept is presented with a few clarifying remarks. Attention is drawn on factors that may disturb the understanding of actual scale effects, like sampling bias or disturbances, and the change of testing techniques, load conditions and sample geometries.

Data regarding the determination of rock, joint and rock mass mechanical properties for different rock engineering projects are reviewed from the point of view of the influence of the sample size on the determination of the deformability and strength properties (mean values and scattering parameters). Attempts to establish significant site especific links among results at different scales are made as well.