Abstract
The research on dynamic mechanical properties of rocks under high temperature is the basis for safe and efficient implementation of deep coal mining and underground coal gasification engineering. In this paper, the split Hopkinson bar (SHPB) with real-time high-temperature function was adopted to systematically study dynamic mechanical properties of sandstones. The research showed that under the condition of a fixed temperature, with the increase of strain rate, the dynamic compressive strength and dynamic peak strain of sandstone increased gradually, and the variation of dynamic elastic modulus with strain rate was not obvious. With the increase of temperature, the dynamic compressive strength of sandstone increased first and then decreased, the dynamic peak strain increased gradually, and the dynamic elastic modulus decreased overall. The variation law of macroscopic failure mode and energy dissipation density with temperature was revealed, and the change mechanism was explained considering the influence of high temperature on the internal structure of sandstone. Based on the principle of component combination and the theory of micro-element strength distribution, the dynamic statistical damage constitutive model was established, and its parameters had certain physical significance. Compared with the experimental results, the established model can well describe the dynamic stress-strain relationship of sandstone under real-time high temperature.
Highlights
Rock dynamic mechanic problems subjected to hightemperature environment are widespread in mine geotechnical engineering
When the temperature was fixed, the dynamic peak strain and strength of rock increased with the increase of the strain rate, which was basically similar to dynamic response characteristics of rocks at room temperature [7]
The following conclusions were obtained: (1) The stress-strain curve of sandstone in hightemperature environment was mainly composed of elastic deformation stage, inelastic deformation stage, and failure stage
Summary
Rock dynamic mechanic problems subjected to hightemperature environment are widespread in mine geotechnical engineering. In the early-stage research on the dynamic mechanical properties of rock under real-time high temperature, the sample was heated to the specified temperature in the heating furnace and was quickly transferred to the SHPB system for dynamic test. Zhang et al systematically investigated thermal damage and energy evolution characteristics in process of impact failure of sandstone after high-temperature treatment and pointed out that the thresholds of damage strain energy release rate of sandstone sample are 200°C and 800°C [26]. Wang et al conducted the static and dynamic compression tests on granite after heat treatment and defined the rate of energy dissipation change, which could be used to identify the deformation stages of rocks and determine positions of failure points in the stress-strain curve [29]. The research results are aimed at promoting the development of mine geotechnical engineering under high-temperature environment
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