Influence of confining pressure and impact loading on mechanical properties of amphibolite and sericite-quartz schist

In order to investigate the dynamic mechanical properties of amphibolite and sericite-quartz schist under confining pressure, two rocks are subjected to impact loadings with different strain rates and confining pressures by using split Hopkinson pressure bar equipment with a confining pressure device. Based on the experimental results, the stress-strain curves are analyzed and the effects of confining pressure and strain rates on the dynamic compressive strength, peak strain and failure mode are summarized. The results show that: (1) The characteristics of two rocks in the ascent stage of the stress-strain curve are basically the same, but in the descent stage, the rocks gradually show plastic deformation characteristics as the confining pressure increases. (2) The dynamic compressive strength and peak strain of two rocks increase as the strain rate increases and the confining pressure effects are obvious. (3) Due to the effect of confining pressure, the normal stress on the damage surface of the rock increases correspondingly, the bearing capacity of the crack friction exceeds the material cohesion and the slippage of the fractured rock is controlled, which all lead to the compression and shear failure mode of rock. The theoretical analysis and experimental methods to study the dynamic failure mode and other related characteristics of rock are useful in developing standards for engineering practice.