Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Abstract

Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities. Firstly, validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars. The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied. It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation. Wave attenuation as well as time delay is affected by the length, quantity, specific stiffness of the distributed microcracks as well as the incident stress wave frequency. The storage and loss moduli of the defected rock are also affected by the microcrack properties; however, they are independent of incident stress wave frequency.

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.…”

“…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).…”

The Relevance Research on Tension Test Technology of Cable and Suspender

“…W.X. Ren, G. Chen [17] considered the influence of the sag and bending stiffness of cable, and calculated the tension by the fundamental frequency of a practical formula based on the energy principle and the curve fitting method. The scope of formula application was also discussed.…”