Mechanical property of granite from different buried depths under uniaxial compression and dynamic impact: An energy-based investigation

Abstract

Mechanical properties of rock play a basic and important role in rock dynamic disaster prevention and control as well as rock engineering design and construction. Buried depth is one of the vital factors affecting rock mechanical properties. To study the energy evolution rules during rock failure at different buried depth, static loading experiments under uniaxial compression and dynamic impact experiments at different strain rates and confining pressures were carried out on six groups of granite specimens with different buried depth. Meanwhile, fractal characteristics of rock specimens crushed at different strain rates were also described in the paper. The results indicate that in uniaxial compression experiments, the dissipation energy and energy dissipation rate of rocks show a quadratic curve with the increase of the depth. Moreover, the amount of the dissipation energy during the rock failure is closely related to the buried depth of the rock specimens. In dynamic loading impact experiments, the incident energy, transmitted energy, dissipation energy and absorption energy increase with the rising strain rate and confining pressure. The reflected energy of rock specimens goes up with the increase of the strain rate, while they decrease with the rising confining pressure. As the strain rate gets larger and larger, the fractal dimension increases gradually. The growth amplitude of fractal dimension for the deep rock specimen is significantly greater than that for the shallow one. The specimen fragmentation degree is smaller and smaller, and the fragment particle size gets more and more uniform. From the relationship between various energy and fractal dimension for rock specimens from different buried depth, it can be known that within the buried depth of 750 m~950 m, the k value of incident energy density, transmitted energy density, dissipation energy density and unit absorption energy gradually decrease with the increase of the buried depth. However, within the buried depth ranging from 950 m to 1250 m, the k value of the above energy increases as the buried depth grows.