Dynamic Indirect Tensile Strength of Sandstone Under Different Loading Rates

Rock failure generally refers to the process of damaging rock material to the point at which it partially or completely loses its load-carrying capacity. For rock materials, the fracture pattern and mechanical properties, including compressive strength, tensile strength, shear strength, and fracture toughness, under dynamic loads are affected by the loading rate/strain rate. This rate effect has been studied experimentally by many researchers, e.g., Grady et al. (1977), Chong et al. (1980), Blanton (1981), Masuda et al. (1987), Chong and Boresi (1990), Zhao et al. (1999), Zhao and Li (2000), Li et al. (2005), Wang et al. (2006), and Dai et al. (2010a, b). Tensile failure is the simplest and most common failure mode found in nature. A good understanding of the dynamic tensile failure of the rock material is important for rock structures subjected to dynamic loads. A comprehensive review on the dynamic testing of rock material has been provided by Zhao (2011). To quantify the dynamic tensile strength of rock material, researchers typically use the Brazilian disc (BD) specimen or semicircular bend (SCB) specimen in the split Hopkinson pressure bar (SHPB) system. Different types of rocks have been tested, e.g., Bukit Timah granite (Zhao and Li 2000), marbles (Wang et al. 2006), Laurentian granite (LG) (Dai et al. 2010a, b), and argillites (Cai et al. 2007). In this study, a series of dynamic indirect tensile tests was conducted on sandstone from Changsha, China. The tests were performed at loading rates of 10, 10, 10, 10, and 10 MPa/s to cover both the quasi-static and dynamic loading conditions. The experimental data show an apparent dynamic effect of the indirect tensile strength of the Changsha sandstone, which can be used in dynamic constitutive models and for the validation of existing or novel numerical models. Based on the experimental data, a new empirical equation is developed to describe the dynamic increase factor (DIF) of the indirect tensile strength of the Changsha sandstone. Moreover, the recently developed distinct lattice spring model (DLSM) (Zhao 2010; Zhao et al. 2011) is validated using the experimental data.