For the frozen thawing rock mass in the engineering practice

taking the initial damage state of rock as the baseline state

the damage caused by freezing thawing and loading is considered as meso damage

and the damage caused by joints is regarded as macroscopic damage. According to the hypothesis of Lemaitre strain equivalence

a composite damage model of jointed rock mass considering macro and micro defects was derived. The effect of the penetration rate and the number of freezing and thawing on the deterioration of mechanical properties of rock mass was analyzed by this model. The results show that when the penetration rate was constant

the damage evolution curve increased with the increase of freeze-thaw times

and the experimental and theoretical peak strength (or modulus of elasticity) curves decreased with the increase of freeze-thaw times. When the freeze-thaw times were constant

the damage evolution curve was positively correlated with the penetration rate

and the experimental and theoretical peak strength (or modulus of elasticity) were negatively correlated with the penetration rate. It indicates that the penetration rate and the freezing thawing times have a certain effect on the deterioration of the rock mass

and the freezing thawing effect of the saturated test group is worse than the natural test group. The calculated results of the model were compared with the experimental values

and the theoretical curves are in good agreement with the experimental curves

which verified the rationality and validity of the model.