Quantifying a new form of acoustic creep in rocks and concrete

• DOI: 10.1121/1.428780
• Publication Date: 2002-07-26T14:08:44Z
• Authors: Eric Smith; James A. TenCate; Robert A. Guyer
• Keywords: 03 medical and health sciences; 0305 other medical science

A new form of nonlinear elastic response, which we call ‘‘slow dynamics,’’ has recently been found to scale universally in all sandstones, limestone, and concretes we have tested. Slow dynamics is unique among known creep processes; the elastic modulus and inverse loss tangent drop in response to harmonic acoustic stress, so the response violates the symmetry of the source. We show here that the slow dynamic recovery rate is a function of temperature, consistent with a thermal activation model for creep requiring a spectrum of energy barriers. We also show that short-term modulus drop, with slow dynamic recovery, accompanies temperature change of either sign, again violating the source symmetry. These two modes of activation are compared quantitatively, and suggest a common origin for slow dynamics in disequilibrated internal strain fields. [Work supported by the Department of Energy: Office of Basic Energy Sciences and IGPP, the Institute for Geophysics and Planetary Physics at Los Alamos.]