Expanding the advantages of flattened ring geometry,a new test specimen geometry with a longer fracture path was advised to investigate the complete dynamic fracture process. This geometry was cracked eccentrically holed flattened disc( CEHFD) which was more conducive to study the unstable dynamic crack propagation and dynamic crack arrest. In order to study the mode Ⅰ( opening mode) dynamic fracture process of a rock,CEHFD specimens with strain gauges and crack propagation gauge glued on the specimen's sur...