Experimental Study on Viscoelastic Behavior of Sedimentary Rock under Dynamic Loading

Effective viscoelastic behaviour of rock mass with double-scale discontinuities

“…It arrives at the first peak and then remains stable before it increases again at a higher frequency. This is different from the viscoelastic behaviour of a rock mass containing microdefects only, in which the second rising slope does not exist when the frequency further increases (Ren et al 2011; Fan et al 2012). The effective storage modulus with double‐scale discontinuities increases again sharply and then reaches the second peak.…”

“…3(a). To investigate the effective behaviour of the rock mass, the microdefected rock is modelled as an equivalent viscoelastic medium (Robertson 1964; Fan et al 2012) and the macrojoints are modelled explicitly as a physical discontinuity. Fig.…”

“…The difference of displacements in the two homogeneous viscoelastic mediums equals to the deformation of the macrojoints, whereas the stress field in front of and behind of the macrojoints is assumed to be continuous (Pyrak‐Nolte et al 1990b; Cook 1992). Therefore, the transmitted wave of the harmonic wave given in propagating through the REV can be obtained as (Fan et al 2011, 2012) where, k n is the normal stiffness of the macrojoint, E* is the dynamic viscoelastic modulus, and S is the length of the REV. The subscript d denotes the parameters of microdefected rock.…”

“…3. The viscoelastic behaviour of microdefected rock is referenced to the experimental research performed by Fan et al (2012).…”

“…Besides, the first peak value of increases with the increase of the macrojoint stiffness, whereas the second peak value of decreases with the increase of the macrojoint stiffness. The phenomenon indicates that the behaviour of the rock mass containing double‐scale discontinuities approaches that of the rock block containing microdefects only when the stiffness of the macrojoint is large enough, in which the peak value of occurs in the initial frequency range spanning from 10 0 Hz to about 10 1 Hz (Ren et al 2011; Fan et al 2012). If the stiffness of the macrojoint is small enough, the viscoelastic behaviour of the rock mass containing double‐scale discontinuities is close to that of a rock mass with linear elastic rock joints, for which the peak value of the loss modulus occurs in the frequency range from 10 2 to 10 4 Hz (Pyrak‐Nolte 1990b; Zhao et al 2006).…”