SOME RESULTS CONCERNING THE VISCOELASTIC RELAXATION OF PRESTRESS IN A SURFACE ROCK ANCHOR

This paper investigates the axisymmetric interactive behaviour of a rigid circular plate anchored to a half spaceregion susceptible to creep. The anchoring load corresponds to a distribution of Mindlin type forces, of finite length, located along the axis of symmetry. The creep behaviour of the halfspace region is represented by a linear viscoelastic material with elastic dilatational behaviour and distortional behaviour of the three-parameter solid type. Using this particular idealization, solutions are developed for the loss of prestress in an anchor bolt subjected to a displacement which is a step function of time. The prestress load at the anchor region is assumed to be distributed in a uniform, linear or parabolic fashion. The numerical results presented herein illustrate the manner in which the decay of the prestress load can be influenced by the length, depth of location and load distribution in the anchor region and the creep characteristics of the halfspace region. © 1979.