The effects of some environmental conditions on the mode I fracture toughness of rocks

Fracture toughness is an important parameter in determining the fracture mechanism of rocks, concretes and other composites, and it is used in performing design and stability analyses. In this study, the aim was to determine the effects of different environmental conditions (dry, saturated, freezing, thermal shock and thermal aging) on fracture toughness and fracture energy values of rocks from three different origins: gabbro, recrystallized limestone and limestone. In the first stage, the physical, chemical, mechanical, mineralogical and petrographic properties of rocks were determined. The material properties of rocks were revealed by physico-mechanical tests, XRD, XRF and petrographic analysis. In the second stage, the rocks were aged by exposing them to pre-determined environmental conditions for a certain period of time and then, semi-circular bending strength tests were applied to the aged rocks. SEM images were taken to determine the effects of different environmental conditions on surface cracks. According to the experimental results, thermal shock, thermal ageing and water saturation conditions led to decreasing fracture toughness, while freezing conditions led to increasing fracture toughness. It was determined that thermal shock was the environmental condition that caused the most weakening. In freezing conditions, it was observed that physico-mechanical properties and fracture toughness values of rocks increased. It was seen that the fracture toughness values of the monomineralic structured samples were more affected by the environmental conditions than the multimineralic rocks.