Study On Dynamic Capabilities Of Rock Materials

Experiments of granite and concrete in high strain-rate unaxial compressive loading were produced in the modified split Hopkinson pressure bar (SHPB) with copper as the pulse shaper. It can be used to ensure the symmetrical stress in the specimens before fracture and avoid the fluctuation of test data due to input shaky stress pulse. Based on the results of the dynamical experiments and the theoretical analysis with the dynamic microcrack model and constitutive model theory, the relations and rule between the microcosmic frame and macroscopical mechanics characteristic of rock materials are discussed adequately. Furthermore, the optimization method based on the mixed genetic algorithmsand numerical analysis with the finite difference methods on rock materials are used to validate the results of the theory analysis. The research method can be applied to the other brittleness materials and laigh impedance materials. The main content in this thesis can be shown as follow:The results of dynamic experiments on rock materials show that not only the compression strength of granite and concrete increase, but also the fragment size decrease and fragment numbers increase with the increasing strain rate. On the other hand, the results of experiments show also that the failure of the granite cylinder is typical tensile splitting failure mode by sudden splitting parallel with the direction of uniaxial compressive loading at different strain rates. Through analyzing contrastively the stress-strain curves, the energy absorbency-time curves and the energy absorptivity-time curves of granite with concrete, it is illuminated the brittleness, impedance, compression deformation capability of rock-like materials is crucial factor on the dynamic fracture.The numerical calculation based on a dynamic interacting sliding microcrack model is adopted to investigate quantificationally the influence on the macro-mechanics properties of rock materials from microcracks included the different initial crack length, crack angle, crack space and friction coefficient under different strain rates. Accordingly, the strain-dependency of mechanics characteristic on rock materials can be explained reasonably.Based on the statistical damage theory and constitutive model theory, the non-linear elastic and viscoelastoplastic dynamic constitutive relation of rock materials are constructed. The characteristic parameters of the dynamic constitutive model of rock materials are ascertained with the inverse analysis method with the adaptive hybrid genetic algorithms.The non-linear elastic stress wave and viscoelastoplastic stress wave equation are derived with constitutive equation of rock materials and stress wave theory. Numerical simulation programs on the dynamic mechanics characteristic of rock materials based on the stress wave equation are programmed. Through contrastively analyzing the results of Numerical simulation and experiments, the correctness of the theory analysis on the dynamic mechanics characteristic of rock materials and the stress wave equations can be testified.