A Nonlinear Viscous Elastic-plastic and Creep Model of Rock Sample

Creep is one of important rock mechanics characteristics.Based on rock stress-strain curve along complete path,a non-linear viscous elastic-plastic and creep model was set up.State equation,physical equation and creep regularity in constant stress and permanent rate stress were obtained.With rock rheologic exponential,this creep model could better behave 3-stage creep proceeding,especially accelerating creep stage.Analytic expressions of creep deformation,creep speed and creep acceleration of rock sample were given.Analysis results were shown as follow.In permanent rate stress,once stress of rock sample was greater than long-term strength of rock,rock sample would reach acceleration creep stage.However,in constant stress,rock sample could reach acceleration creep stage only after certain time.This time was much related to rock mechanics characteristic.