In this study, the dynamic loading apparatus, which uses the electric detonator, was applied to load the rock specimens diametrically. The dynamic tensile-splitting behavior of the sandstone samples was observed by high-speed video camera and the applied load histories were monitored by an impact load cell. High-resolution X-ray computed tomography (CT) system, which use micro-focus X-ray beam, has been used to observe microstructure of rock samples. This study used the cone-beam scan of micro-focus X-ray CT to observe the 3D fracture pattern of the samples. The dynamic fracture processes of rock in dynamic tensile splitting test were analyzed by the numerical simulation method to investigate the influence of the loading condition on the tensile-splitting fracture. Additionally, this study validated the applicability of the dynamic loading apparatus to estimate dynamic tensile strength of rocks such as sandstone and tuff.
Information regarding the dynamic tensile properties of rock material is of considerable importance in assessing the stability of rock structure under dynamic loading. It is also essential to understand how fractures initiate and propagate under different loading conditions in order to determine rock breakage and fragmentation in rock blasting and percussive excavation. The dynamic behavior of brittle materials, including rocks and concrete, show complex fracture patterns and fracture processes when they are subjected to high strain rate loading. Fractures may occur from pre-existing flaws or micro-cracks under applied stress condition (Grady & Kipp 1980). Cho et al. (2003) showed using experimental and numerical approaches that the loading rate dependency of dynamic tensile strength of rock is caused by the inhomogeneity of the rock. Tedesco et al. (1993) have carried out dynamic tests of rock using apparatus such as Split Hopkinson Pressure Bar (SHPB). They however assumed that dynamic stress field in the investigations is the same as its static one.
