Research On The Fatigue Damage And Fracture Of Solo-joint Rocks Under The Freezing-thawing And Loading-unloading Cyclic Condition

In recent years,more and more projects have involved cold areas with the development of China's construction projects.Rock is the most important part of geological engineering,including the cracks caused by natural damage.In the areas where the underground rock fissures are relatively developed,the temperature variation caused by the seasonal and day and night alternation causes the cracks in the rock mass to freeze and freeze.Therefore,it is of great value to study the damage evolution and fracture characteristics of fractured rock mass under the repeated action of the freezing-thawing and loading-unloading.It was prepared that a single fracture standard specimen with0°,45 °,and 90°.Through the freezing and thawing cycles of 10,20,30 and 40 times,the flakes and cracks were observed in different stages.The localized damage effect caused by the single fracture angle under the same freezing and thawing cycle is weakened with the increase of the angle.The effect of localized damage on the same angle single fracture specimen increases with the increase of freeze-thaw cycle.The freeze-thaw cycle has a similar equivalent damage to the local are except the single fissure.Then,the specimen is subjected to different stress level conditions and cyclic loading-unloading,and the hysteresis curve under cyclic loading is obtained.Three typical failure modes are obtained by analyzing the macroscopic model of single fracture rock mass.The strength of single slit inclination rock under the same freezing and thawing cycle is analyzed.In the theoretical analysis,the temperature of the specimen during the freeze-thaw process is measured in real time,the temperature change curve in the process of freezing and thawing is obtained,the theory of frost heave force evolution is analyzed,and the expression of frost heave force is given.According to the theory of rock fatigue and fatigue theory,the cumulative fatigue damage analysis of single cracked rock mass.Based on the basic theory of fracture mechanics,the mechanism of crack propagation under the combined action of frost heave force and uniaxial cyclic load is discussed.Finally,the expressions of I and II crack stress intensity factors are proposed considering the effect of freeze-thaw damage on the increase of crack length and the deterioration of material properties.FC software is used to simulate simulate and analyze the three kinds of single crack angles and freeze-thaw cycles under the condition of freezing thawing and loading unloading,the results are consistent with the experimental results.The evolution process of single fractured rock mass under this condition is systematically analyzed by combining the experimental analysis and the theoretical deduction of single fractured rock mass under the combined action of freezing-thawing and loading-unloading.It provides some reference value for disaster prevention and protection project in the corresponding cold zone.