A nonlinear creep damage model for brittle rocks based on time-dependent damage

Abstract

Many experiments conducted under the three-dimensional stress condition reveal that damage of brittle rocks shows obvious deformational and time-dependent effect. Based on triaxial rheological test results, the creep behaviours and creep rupture characteristics of metamorphic volcanic fine conglomerate were investigated. It is found that the test results agree well with numerical curve, and the relationship between creep damage variable and loading time can be fitted by an exponential function. By analysing the tertiary creep, a new nonlinear viscoplasticity model on the basis of creep damage was proposed, and then, the three-dimensional nonlinear creep damage constitutive equations were deduced and validated by tests. Comparisons between numerical predication and test data show that this nonlinear creep damage model is valid and reasonable. Therefore, it can better describe the complete creep phases of the metamorphic volcanic fine conglomerate, which include primary creep, secondary creep and tertiary creep.

Keywords:

• rock mechanics
• creep characteristics
• creep damage variable
• nonlinearity
• constitutive equation
• time-dependent damage

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (11172090, 51209075 and 51109069) and the Major State Basic Research Development Program of China (‘973’ Project 2011CB013504).