Design of rock material parameters by cracked straight through Brazilian disc

•The stress distribution pattern of cracked straight through Brazilian disc (CSTBD) under loading is simplified.•The expression for nominal stress σn is derived, and the equation for equivalent crack ae for CSTBD is suggested.•A design method for obtaining rock material parameters (ft & KIC) simultaneously for CSTBD specimens is proposed.•A simple closed-form solution for CSTBD is proposed to obtain the material parameters (ft & KIC).