E is a key figure for the description of rock deformation behaviour. It quantifies the material stiffness under uniaxial conditions with S11 (in the case of a fluid saturated porous rock σ11) as the only non-zero stress. Nevertheless, it can be determined with any kind of compressional experiment, may it be uniaxial and unconfined (UCS test) or triaxial (so called single-stage and multi-stage experiments) using cylindrical test plugs with a length to diameter ratio of 2:1. Young’s modulus is determined as the gradient of the load path in a stress-strain (or σ-ε) diagram of an unloading-loading hysteresis carried out as soon as the stress-strain curve of the experiment has reached the linear part. The corresponding equation is Hooke’s law applied to the axial stress and axial strain:
E = ΔS11/Δε11 (modified from Zoback 2007).
Young’s modulus usually is given in GPa. Brittle, strong rocks (granite, basalt, gneiss) have a high Young’s modulus in the range of 50 GPa to 100 GPa, weak, (semi-)ductile rocks (poorly consolidated sandstone, mudstone, some shale and marble) have a low Young’s modulus of 0.1 GPa to 50 GPa.
Recently, the article "Determination of capillary threshold pressure with hydrogen gas" was published in the journal EEK.
Gesteinslabor has successfully completed the development of a new test rig to determine the capillary threshold pressure with hydrogen.