Dynamic tensile failure of rocks under static pre-tension

• SHPB is modified to measure the dynamic tensile strength of rocks under static pre-tension.
• The dynamic tensile strength decreases with the increase of pre-tension.
• The dynamic tensile strength increases with the loading rate.
• The total tensile strength is roughly independent of the pre-tension.

A modified split Hopkinson pressure bar (SHPB) system is utilized to load Brazilian disc (BD) samples statically, and then exert dynamic load to the sample generated by impact. The pulse shaper technique is used to generate a slowly rising stress wave to facilitate the dynamic force balance in dynamic tests. Five groups of Laurentian granite BD samples (with static tensile strength of 12.8 MPa) under the pre-tension of 0 MPa, 2 MPa, 4 MPa, 8 MPa, and 10 MPa were tested under different loading rates. The results show that the rock dynamic tensile strength decreases with the increase of the pre-tension. It is also observed that under the same pre-tension stress, the dynamic tensile strength increases with the loading rate. However, the total tensile strength of the rock is roughly independent of the pre-tension. The failure patterns of the samples also reveal the rate dependence of the dynamic tensile strength of rocks.