Study On Experimental And Mechanical Behaviors Of Rock Under Static-Dynamic Coupling Loads

Due to the shortage of experimental and theoretical research on rock mechanics in deep engineerings, an innovative testing system based on SHPB(Split Hopkinson Pressure Bar) was constructed considering the stress state of rock with static-dynamic coupling loads. It can be used to carry out tests on rock under medium and high strain rate with 0-200MPa static loads and 0-500MPa dynamic loads. The data processing software was developed based on Visual C＋＋language, where the collected signals were denoised with wavelet method.The friction effect, wave dispersion, inertia effect, section accordance, stress equilibrium and constant strain rate of specimen in constructed system and other large diameter SHPB system for brittle materials were analyzed, and the performances of rectangular, tiangle, and half-sine wave were presented to show ways to get perfect loading wave. Based on experiments with novel striker method and wave-shaper method, the expression of required incident wave was deducted. In order to produce arbitrary possible incident wave, an back-design theory was brought forward.Based on Stochastic Finite Element Method, the parameters of SHPB test leading to the scattering of calculated results were discussed. With lots of test results, the mechanical characters of rock were concluded, and the constitutive model was fabricated. After statistics of broken pieces of specimen, the fractal characteristics of rock fragmentation was investigated and the fractal dimension value was reasonablely predicted with renormalization method.Referring to the corresponding researches at home and abroad, there are several points of highlight as follows:a) An innovative testing system was constructed for tests of rock with static-dynamic coupling loads under medium and high strain rate, which supply a platform for research of deep-level rock mechanics.b) The effective way to reduce wave dispersion and realize stress equilibrium of specimen was discussed and the expression of required incident wave for constant strain rate tests was put forward.c) A new way to back-design strker for arbitrary stress wave was established, which leads to the perfection of the theory system of novel striker testing technique.d) The constitutive model of rock under static-dynamic coupling loads was presented, which enriches the rock mechanics for deep engineerings. e) The failure mechanism and the fractal characteristics of rock fragmentation under coupling loads were concluded and the fractal dimension value was reasonablely predicted with renormalization method.