Study on dynamic mechanical response characteristics and fracture energy dissipation mechanism of sandstones with different saturations under real-time low temperature

Abstract

AbstractIt is of great significance to study the mechanical properties of rocks with different saturations for safe and efficient development of geotechnical engineering in low-temperature environments, such as open-pit mining and tunnel excavation in winter in cold areas, and etc. In this paper, the LT-SHPB test system was used to carry out impact loading tests for sandstones with various saturations at − 20 °C environment. SEM was used to observe the cross-sectional characteristics of the specimens. The distributions of fragments were obtained by screening after impact failure. The energy dissipation model was established during the failure process. The research results indicated that the failure strength, elastic modulus, and peak strain of sandstones showed significant strain rate strengthening. Under the fixed strain rate, as the increase of the water content, the failure strength and elastic modulus and the sensitivity increased first and then decreased, while the peak strain showed the opposite change characteristics. 75% saturation was the turning point of the change. The sandstones under saturated water content exhibited remarkable ductile failure characteristics, while the brittle failure dominated in other conditions. The fundamental reason for this change was the difference between the freezing and frost heave effects of water-bearing specimens under low temperature conditions. The change characteristics of the macroscopic damage degree of sandstones with the strain rate and water content were basically the same as the characteristics of mechanical properties. The higher the internal density, the more the dissipated energy and surface specific energy for the whole failure of the specimen. The energy dissipation difference could directly change the macroscopic failure characteristics.