Effect of Hydrostatic Pressure and Heat Treatment on The Sandstone Dynamic Compressive Strength

Available experimental data on the additional external factors that influence the sandstone dynamic fracture are analyzed using the incubation time approach. Compressive strength dependences on loading rate are obtained for hydrostatically compressed and preheated sandstone samples. It is shown that with increasing loading rate, the strength characteristics of sandstone increase for all treatment temperature and hydrostatic pressure values. With increasing hydrostatic pressure, an increase in dynamic compressive strength is observed. A linear increasing relationship is established between the incubation time and the external hydrostatic pressure. The effect of pre-heat treatment on the sandstone dynamic compressive strength is assessed. It was found that heat-pretreated samples have lower compressive strength than samples not exposed to heat for all loading rates. The incubation time values are calculated for each pre-treatment temperature. The compressive strength inversion effect is discussed demonstrating that when comparing two sandstone samples treated at different temperatures one sandstone sample has higher compressive strength under quasi-static loads but is more easily damaged under high-velocity loads compared to the second sample. It is shown that to describe the dynamic fracture considering the influence of additional external factors, such as hydrostatic pressure and heat-treatment, two material constants (incubation time and static compressive strength) are sufficient.