Experimental study of the time-dependent behaviour of fracture propagation in salt rock

This paper presents an experimental study investigating the time-dependent behaviour of fracture propagation in salt rock. The research is aimed at enhancing the understanding of the fracture mechanics of salt rock, which is crucial for applications such as underground storage of hazardous waste and energy storage. Thirteen Wedge Splitting Tests (WST) were performed on salt rock specimens at four different loading rates, complemented by nine uniaxial creep tests on the same material at three stress levels. The WST results revealed major effects of the loading rate on the fracturing process, with decreasing rates leading to increased mechanical work required for splitting and reduced peak splitting force. The produced experimental dataset offers an excellent benchmark for the validation of numerical models including creep and fracture of salt rock. Additionally, the paper includes preliminary finite element simulations incorporating an inviscid discrete fracture representation and linear viscoelastic creep modelling in the bulk material that provide first insights into the origin of the observed loading rate effects. The numerical study concludes that these effects are mainly due to phenomena developed in the fracture process zone. The findings emphasise the need to consider time-dependency in Cohesive Zone Models used for salt rock fracture representation.