Abstract
As part of the rock mass, both the mesoscopic and macroscopic flaws will affect the creep mechanical behavior of the rock mass with nonpersistent joints. This study focuses on this kind of rock mass and establishes a creep damage model to account for the effect of the joint on its creep mechanical behavior. First, on basis of analyzing the rock element creep mechanism and the typical creep deformation curve, a new creep damage constitutive model for the rock element is set up by introducing the damage theory and Kachanov damage evolution law into the classic creep constitutive model such as J body model. Second, the determination method of the proposed model parameters is studied in detail. Third, the calculation method of the macroscopic damage caused by the joint proposed by others is introduced which can consider the joint geometry, strength, and deformation parameters at the same time. Finally, the creep damage model for the rock mass with nonpersistent joints under uniaxial compression is proposed. The calculation examples indicate that it can present the effect of the joint on the rock mass creep mechanical behavior.
Highlights
On basis of the existing research studies on the creep mechanical behavior of the rock element, some investigations on that of the rock mass is in progress
Kachanov creep damage theory is firstly introduced into the classic creep model such as J body model to set up the creep damage model for the rock element which can simulate the accelerating creep stage
One is the steady creep deformation for instance curve I in which the creep rate gradually decreases to 0, and the creep deformation gradually tends to be constant when the applied load is less than the rock element long-term strength. e other is the unsteady creep deformation for instance curve II in which the creep rate gradually increases, and the creep deformation gradually increases and eventually the rock element failure occurs when the applied load exceeds the rock long-term strength. erefore, the creep strain is usually described as a unitary process represented by the sequence of specific timedependent deformations: the instantaneous elastic strain, the ε D
Summary
One is the steady creep deformation for instance curve I in which the creep rate gradually decreases to 0, and the creep deformation gradually tends to be constant when the applied load is less than the rock element long-term strength. E other is the unsteady creep deformation for instance curve II in which the creep rate gradually increases, and the creep deformation gradually increases and eventually the rock element failure occurs when the applied load exceeds the rock long-term strength. Erefore, the component which can reflect the rock element creep damage should be adopted to describe the accelerating creep stage. (ii) e steady creep stage of the rock element in practice is approximately linear, and its corresponding deformation rate is assumed to be the average of the curve’s slope. (iii) During the accelerating creep stage, the rock element damage will become worse and worse and eventually fail. e time tF when the rock element creep failure occurs is called the rock element creep lifetime where the slope of the creep curve is infinite and the rock element damage is 1
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