Experimental and numerical investigation of dynamic tensile behavior of granite-concrete bimaterials with different rough interfaces

Shotcrete is a vital support measure for ensuring the stability of the surrounding rock in tunnels. Rock-concrete structures may experience potential tensile failure under dynamic loadings. The effects of the interface fractal dimension, loading angle, and loading rate on the dynamic tensile properties of granite-concrete samples were studied by experimental and numerical solutions. The results showed that the dynamic tensile behavior of bimaterials was related to the interface stresses. The increasing rate of the dynamic nominal tensile strength (DNTS) significantly decreased when the loading angle theta >= 45 degrees. The influence of interface roughness on DNTS was the most significant at 0 degrees and the least significant at 90 degrees. The DNTS of the granite-concrete bi-material sample with a smooth interface was 6.97 MPa at 0 degrees, and the DNTS increased to 13.15 MPa at 90 degrees. When D = 2.114, the DNTS was 23.63 % higher than that of the smooth interface, and the enhancement coefficient was less than 4 % at 90 degrees. Furthermore, there was a positive correlation between the loading angle and fractal dimension with the increased dissipated energy. Moreover, the loading rate effect on the tensile properties of granite-concrete specimens was studied based on the FLAC(3D)-PFC3D coupling. The DNTS of the granite-concrete sample with a loading angle of 45 degrees and a rough interface fractal dimension of 2.169 was 11.64 MPa at 124.58 GPa s(-1), and only increases by 11.86 % when the loading rate increases to 245.28 GPa s(-1). The DNTS and Wa were influenced by the loading rate significantly at 0 degrees, 15 degrees, and 90 degrees, while the loading rate at angles of 45 degrees similar to 60 degrees had the lowest impact on DNTS and W-a. Finally, the deviation between the calculation results based on the Brazilian splitting equation and the stress monitored in the numerical simulation was analyzed.