The effect of loading mode and thermal cycling on fracture characteristics in dolomite rock

Abstract

The impact of repeated low-temperature thermal cycles on dolomite rock’s thermomechanical behavior was examined, with a focus on how loading mode and cycle number (N) affect its properties. Dolomite samples were subjected to 0, 50, 100, and 500 thermal cycles, with fluctuations between 20 and 60 °C being applied. Tensile strength, fracture toughness, elastic modulus, fracture velocity, and ultrasonic wave speeds were measured before and after the thermal cycles. An initial improvement in dolomite’s performance was shown, with a peak reached around 336 cycles, followed by deterioration between 336 and 500 cycles. Specifically, increases of approximately 25.11% and 32.5% in pure modes I and II fracture toughness, respectively, were observed at optimal cycle numbers, before a decrease was seen at 500 cycles. Higher elastic modulus, fracture velocity, and acceleration were exhibited by mode II specimens compared to mode I. No phase changes or chemical decomposition within the rock were indicated by X-ray diffraction and chemical analysis. The influence of mineral expansion and microcrack generation on the dolomite’s structure was revealed by ultrasonic wave tests. The findings highlight how temperature fluctuations affect rock masses, which is crucial for understanding dolomite’s vulnerability to damage from thermal stress and loading conditions. (Figure presented.)

keywords: dolomite, elastic modulus, fracture speed, pure mode I, pure mode II, thermal cycles