Experimental Study on the Directional Effect of Damage in Marble Under Different Impact Modes

The surrounding rock of a tunnel is subjected to cyclic impacts from different directions in tunnel engineering construction, resulting in directional damage to the rock mass. To investigate the impact direction effects on damage, a split Hopkinson pressure bar (SHPB) system was utilized to conduct cyclic impact tests on marble. The dynamic mechanical response of the marble was analyzed under different impact directions and loadings. Additionally, the P-wave velocity and pore distribution of damaged marble under different modes were obtained. The results showed that the P- wave velocity of marble decreased with the increasing impact times and loadings, while the porosity increased. The P-wave velocity of marble in Mode I was generally lower than that in Mode II, while the porosity was higher than that in Mode II. At an impact loading of 98 MPa, the porosity of marble subjected to three impacts was 3.21