ABSTRACT
The difference between dynamic (Edyn) and static (Estat) Young’s Modulus for granular material such as rock is well known in rock engineering (van Heerden, 1977; Lama & Vutukuri, 1978; Barton, 2006). Ratios for Edyn/Estat are typically in the range from 1 to 2 (Eissa & Kazi, 1988) sometimes up to 4 (Henriksen et al., 1999). There exist some empirical correlations between Estat and Edyn (e.g. Fjær 1999).The difference between Edyn and Estat is generally attributed to different frequencies, strain and stress amplitudes. Plona and Cook (1995) explain this with the strain amplitudes being 10−7 for dynamic tests and 10−2 to 10−3 for static tests. This notion is supported by Tutuncu et al. (1994) and Hilbert et al. (1994), to name a few. However, Ciccotti and Mulargia (2004) report opposite observations.ThedifferencebetweenEdyn andEstat appear to get larger with increasing confinement and decreasing porosity (Bathija et al., 2009). Fjær (2009) discusses the elastic moduli during cyclic deformation tests and notes that at load reversal Edyn and Estat are very close. Finally, Olsen et al. (2008) observe that the elastic moduli depend on the type of strain measurement, i.e. strain gage measurements lead to higher moduli compared to LVDT measurements. This literature review motivated an experimental investigation onmainly sandstones by cyclic compression tests with different frequencies/loading rates.
