Testing And Numerical Simulation Primary Study On The Damage Characteristics Of Cracked Rock In Cold Region

The research of damage characteristics of cracked rock in cold region is one of the fundamental projects in the rock mechanics research field in cold region. With the rock mechanics testing system RMT-150B and CT special testing equipment of geotechnical damage mechanics, the primary macro-testing and meso-testing of damage characteristics of red sandstone sample and prefabricated cracked red sandstone sample are completed, and emphasis are given to meso-damage characteristics of the prefabricated cracked red sandstone sample. The results of the meso-testing were analyzed with the fork and chaos theory. Considering the coupled action of temperature and stress fields, and using elastic-plastic finite-element method, the effect of interfaces and job practice on the stability of the tunnel in cold region are studied. The contents are as follows:(1) Under the negative temperature and the room temperature, the primary macro-testing and meso-testing of prefabricated cracked red sandstone on failure mechanism under uniaxial compression, triaxial compression and fatigue loading are completed. The results show that as the main cause to the rock damage and the emergence of crack, prefabricated crack reduces the strength of rock, and it controls the damage process of rock. The process of endurance failure of cracked rock is controlled by stress-strain curve and threshold value of cracked rock endurance failure.(2) The results of real-time CT testing are analyzed with fork and chaos theory. The results show that the change of CT number during damage process of prefabricated cracked rock can be described by Logistic equation. So, the damage process is going with fork and chaos characteristics.(3) The finite element analysis on the deformation law of the temperature and stress fields coupling of the surrounding rock in cold region are completed. The results show that the sub-step excavation construction method will reduce evidently the phenomena of stress concentration during the process of tunnel excavation construction in cold region and enhance safety coefficient of construction. Both the stress concentration and deformation increase evidently because of the interface which is also a key factor to the disaster of projects. The results also show that the manual refrozen method is effective to enhance the strength of surrounding cracked rock, reduces the pressure of the surrounding rock which the lining bears, and is beneficial to the tunnel safety during the construction and operation.(4) According to the primary damage law of cracked rock in cold region, the reasonable job practice and preventive measures of frozen damage of tunnels in cold region had been suggested.