Mechanical properties and energy evolution of thermally damaged red sandstone in high-strain-rate impact tensile tests: Experimental and theoretical analyses

The dynamic tensile strength of rocks affects structural stability in geotechnical applications requiring thermal resilience. This study employs a large-diameter (Φ75 mm) split Hopkinson tension bar ( SHTB ) to perform high-strain-rate tensile tests on red sandstone specimens subjected to thermal treatments at temperatures up to 1200 °C. However, specimens heated to 1200 °C transitioned to an amorphous melt phase, making tensile tests infeasible. The novel large-diameter SHTB technique improves the test efficiency by using double reinforcement and an adhesive to attach the specimen to the bar. An energy-based damage variable and a comprehensive rock brittleness index are used to assess the effects of the strain rate and thermal conditions on the specimens' mechanical behavior and energy dissipation. Further, an innovative dissipated energy model ( T II ) describes the intrinsic nonlinearities of the rock's dissipated energy dynamics and their crucial influences on the pre-peak stress responses. A dual-threshold model is utilized to describe thermal strengthening or weakening, revealing fundamental insights into the energy mechanics of rock failure, which are vital for the integrity of high-temperature geotechnical systems.