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Abstract The concepts of the mesoscopic damage caused by freezing and thawing，the mesoscopic damage caused by loading and the macroscopic damage caused by joints were proposed for the jointed rock in cold regions. The compound damage variable of jointed rock considering the coupling of the macroscopic and mesoscopic flaws was deduced based on the strain equivalence hypothesis of Lemaitre under freezing-thawing and loading conditions. Defining the initial damage state of intact rock as the basic state，a constitutive model considering the freezing-thawing and loading damage for jointed rock was established. Finally，the experimental data was adopted to test the validity of this model. The mesoscopic damage caused by freezing-thawing was found to be a cyclical process of fatigue damage and to increase approximately linearly with the freezing-thawing cycles. The mesoscopic damage caused by the single freezing-thawing cycle was small，and was called the local damage. The mesoscopic rate of damage caused by loading varied unevenly in the process of strain increasing and reached the maximum at the peak strain. The macroscopic damage of rock with precast joints exhibited significant anisotropy and decreased with the freezing-thawing cycles. The joint properties and the freezing-thawing cycles were the critical factors for the weakening of anisotropy. The mechanical properties of jointed rock under loading in cold regions were determined by the mesoscopic damage of freezing-thawing，the mesoscopic damage of loading，macroscopic damage with joints and the coupling effects. The frost resistance of jointed rock was described well with the compound damage variable of freezing-thawing and loading.
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2015, Vol. 34 
