MECHANICAL DAMAGE TEST AND MODEL STUDY OF LAYERED COMPOSITE ROCK CONSIDERING TEMPERATURE EFFECT

In order to study the mechanical characteristics of layered composite rocks under high temperature, the layered composite rocks prepared by similar materials were heat treated at 20°C (room temperature), 100°C, 200°C and 300°C, and the physical and mechanical parameters were obtained by uniaxial compression tests. The results show that the mass change rate and volume expansion rate of the layered composite rock present an upward trend with the increase of temperature, and the growth is obvious at 100°C. It is found that the peak strength and elastic modulus tend to deteriorate and decrease linearly, and the peak strain is positively correlated with temperature by fitting the empirical formula of various mechanical parameters. With the increase of temperature, the layered composite rocks show shear-slip failure, and the single type rocks transform from shear failure to tension-shear failure. The number of microcracks grows during failure, and the ductility characteristics are significant at 300°C. A constitutive model of rock considering temperature effect is introduced and the stress-strain curves at different temperatures are fitted. The model can well characterize the damage evolution law and failure characteristics of layered composite rock after heat treatment, and reasonably reveal the damage mechanism of layered composite rock after high temperature.