Study on Dynamic Mechanical Properties and Failure Mechanism of Sandstones under Real-Time High Temperature

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.

Experimental study on the quasi-static and dynamic tensile behaviour of thermally treated Barakar sandstone in Jharia coal mine fire region, India

“…Xu et al 19 investigated the thermal effect on rock fragmentation characteristics of Laurentian granite using a dynamic ball compression test and concluded that dynamic tensile strength is continuously decreasing with increasing temperature due to thermal damage. Furthermore, Zhang et al 20 found an increasing trend in the compressive strength of sandstone up to 400 °C, which then decreased with increasing temperature. Fan et al 21 evaluated the three cooling methods on the dynamic properties of sandstone and concluded that compressive strength increases up to 200 °C and sharply reduces afterwards for natural cooling due to the improved compactness of sandstone.…”

A New Index of Energy Dissipation Considering Time Factor under the Impact Loads

“…Li et al [18] found a correlation between the various patterns of energy dissipations and the development of microcracks. In the study of Zhang et al [19], the energy dissipation density as an important parameter of the damage variable can better express the dynamic stress-strain relationship of sandstones under real-time high temperatures. In evaluating energy, energy consumption density as a standard metric has its disadvantage in describing the time effect.…”