LAUSR

Abstract Shotcrete is widely used as a lining support method to enhance the resistance capability of surrounding rock masses in tunnels. For a better design of shotcrete structures, this study developed an optimally designed shotcrete material by utilizing the design-of-experiment (DoE) method. The shotcrete material was well matched with target sandstones collected from 990-m-buried tunnels in terms of physical and mechanical properties such as compression strength, Young's modulus, peak strain, and density. To verify the mechanical performance of the shotcrete material, a series of compression experiments were carried out on sandstone-shotcrete integrated samples. The experimental results indicated that the newly developed shotcrete material resisted compression loading with the sandstone but significantly depended on the orientation and roughness at the interfaces between them. Specifically, three different failure types were identified in the integrated samples: the tensile failure type, the shear failure type and the mixed failure type. Furthermore, when the interface dip angles were low (e.g., α = 0° and 15°) and high (e.g., α = 75° and 90°), the sandstone-shotcrete samples showed a large compression strength, while when the interface dip angles were intermediate (e.g., α = 30°, 45° and 60°), the shear failure that occurred at the interfaces considerably reduced the integrity of the sandstone-shotcrete samples and induced a small compression strength. However, by performing the undulating treatment at the interface between the sandstone and shotcrete, the performance of the integrated samples with medium dip angles (e.g., α = 30°, 45° and 60°) was significantly enhanced, and the optimally designed shotcrete material exhibited its advantages.