Paul A. Johnson
EES-4, MS D443, Los Alamos Natl. Lab., Los Alamos, NM 87545
Universite Pierre et Marie Curie, Bureau des Mecaniques, Tour 22, 4, Pl. Jussieu, 75252 Paris Cedex 05, France
Patrick N. J. Rasolofosaon
Institut Francais du Petrole, Rueil Malmaison Cedex, France
Nonlinear elastic response in rock is established as a robust and
representative characteristic of rock rather than a curiosity. This behavior is
illustrated from a variety of experiments conducted over many orders of
magnitude in strain and frequency. The evidence leads to a pattern of unifying
behavior in rock: (1) Nonlinear response in rock is enormous; (2) the response
takes place over a large frequency interval (dc--10[sup 6] Hz at least); (3) the
response not only occurs, as is commonly appreciated, at large strains but also
at small strains where nonlinear response and the manifestations of this
behavior are commonly disregarded. Nonlinear response may manifest itself in a
variety of manners, including a nonlinear stress-strain relation
(hysteretic/discrete memory), nonlinear dissipation, harmonic generation, and
resonant peak shift, all of which are related. The experiments described
include: quasistatic stress-strain tests (strains of 10[sup -4]--10[sup -1] at
frequencies near dc-1