Damage constitutive law and damage evolution characteristics for fractured rock under coupling action of static and dynamic load

After earthquake, intensive parameters of fractured rock including initial elastic modulus were changed, and its mechanical properties were affected in this process. Based on the Rock Mechanics Testing System(MTS), samples were made with different pre-existing fissures in aspect of fracture angel, spacing and connectivity. In order to simulate the influence of earthquake wave, dynamic load was applied with a certain frequency and amplitude before the uniaxial compression tests. Based on macroscopic statistical damage model, in consideration of the coupling action of initial damage caused by dynamic load and damage caused by static load, getting the damage threshold by least energy consumption principle, the modified damage evolution constitutive equation of fractured rock sample was established, which can correctly describe the stress-strain relationship before peak strength. Through the analysis of relationship between damage variable evolution and characteristic of structure plane, it was indicated that fracture characteristic parameters do not affect the macroscopic constitutive relationship. With the increase of fracture angle, the initial and critical damage variables both increase with an outstanding damage accumulation process. With the increase of connectivity, the initial and critical damage variables both increase. With the increase of fracture spacing, fracture coalescence and failure level become higher, and the initial damage variables are essentially unchanged, while the critical damage variables decrease. ©, 2015, Academia Sinica. All right reserved.