1992 Volume 108 Issue 8 Pages 601-606
Some constitutive equations focusing on time-dependent behaviour of rock have been proposed by early workers. However, most of them can be applied to restricted loading condition, that is, a constitutive equation can be applied to only creep or only constant strain rate test. Moreover, few of them can be solved analytically. This is one of the reasons why the relation of time-dependent behaviour or rheological phenomena between different loading conditions still remains open to discussion.
In this study, a very simple constitutive equation of variable compliance type is discussed, which has been proposed by the author. The constitutive equation can be solved analytically for several loading conditions such as creep, relaxation, constant strain rate, constant stress rate and allows to examine the relations of time-dependent behaviour among these loading conditions.
It is well known that strength increase with loading rate in constant strain rate. Also, it is known that life time in creep decreases with increase of creep stress. By means of analytical solution of the proposed constitutive equation, it is shown that these two phenomena are closely related and life time in creep can be estimated by the result of constant strain rate test. Also, strength obtained by constant strain rate test and constant stress rate, life time of creep test and relaxation test, relation between creep strain and width of stress-strain curve, etc are discussed.
