Experimental Study on Dynamic Mechanical Properties of Sprayed Concrete-Surrounding Rock Combined Body

To investigate the dynamic response problem of the double medium formed by the adherence of sprayed concrete and surrounding rock in the tunnel, a split Hopkinson pressure bar of 75 mm in diameter was adopted at the ages of 3,7 and 10 d. Experimental results showed that dynamic compressive strength and dynamic increase factors (DIF) of the combined bodies increase with the strain rate. With the growth of strain rate, the critical strain of the combined bodies first increases, then deceases. Furthermore, the combined bodies of 3 d reveal the plastic property and brittle property for 7 d and 10 d when the strain rate is over 80/s. The failure characteristic of the sprayed concrete changes from tearing strain damage to crushing damage as the growth of strain rate, and the failure characteristic of rock presents the tensile failure mode as demonstrated by the scanning electron microscope (SEM).