Experimental characterization of contact blast-induced failure transition in natural marble

Contact blast loading of crystalline rocks can produce a rapid transition from localized cratering to macroscopic splitting and back-face spalling. This study experimentally characterizes this transition in natural marble by combining quasi-static mechanical characterization, replicated field contact C-4 blast tests, free-field overpressure measurements, and backface peak particle acceleration measurements. The tested marble showed apparent static isotropy under low-rate loading, with a mean uniaxial compressive strength of 93.2 MPa, elastic modulus of 42.1 GPa, Poisson’s ratio of 0.30, indirect tensile strength of 7.7 MPa, and directional strength variation not exceeding 10.1%. Under contact blast loading, however, the observed failure mode changed from stable local cratering at 50 g to scattered transition behavior at 60 g and consistent macro-rupture at 70 g. The back-face peak particle acceleration increased from 2435.5 g at 50 g to 10,028.1 g at 60 g, indicating activation of tensile reflection and spalling. Comparison with TM5-855-1 showed that crater dimensions were overpredicted for the tested marble blocks; however, the resulting correction ranges are presented only as preliminary, material-specific estimates for the tested geometry and charge configuration. The results provide an experimental benchmark and a cautious mechanics-based interpretation for contact blast-induced failure in bounded crystalline rock blocks.