Nonlinear viscoelastic creep property of rock with time-temperature equivalence effect

The rheological behavior of rock at low temperature in a long time scale equal to that at high temperature in a short time scale is called time-temperature equivalence effect (TTEE). It is convenient to obtain the rheological data in a long time scale through increasing temperature. In order know about the TTEE of rock in nonlinear viscoelastic field, based on the single-integral nonlinear constitutive equation presented by Schapery, the equivalence equation of TTEE on the nonlinear viscoelastic creep property is put forward. According to the creep test data of granite at different stresses and temperatures, setting 20. as the reference temperature, the variation of the vertical shift factor with temperature and the modified compliance curves are obtained through considering the temperature influence on instantaneous creep compliance. The master curves at different pressures and the variation of the horizontal shift factor with temperature are obtained by shifting the modified curves horizontally to make the adjacent curves cross to a point. The coincidence of the master curves is good, which further confirm the existence of TTEE of granite. It is found that the nonlinear property of granite from 40 MPa to 64 MPa is not evident but reaching to 87MPa is distinct.