Abstract: The mechanical behavior of interfaces is a hot research topic in the field of geotechnical engineering. The soil-rock contact surface, as a widely existing interface in various geological bodies, its mechanical behavior is closely related to engineering stability and geological hazard development. Geometric shape is an important factor affecting the mechanical behavior of soil-rock interfaces. Different shapes of soil-rock interfaces were regarded as objects, and the natural contact surface morphology was restored through 3D printing technology. Bedrock models containing rectangular, serrated, and arc-shaped contact surfaces were printed, and soil-rock samples with different interface shapes were prepared. On this basis, indoor shear tests were conducted to investigate the influence of regular interface morphology on the shear behavior of specimens under different asperity widths. The results indicate that: (1) For the same material, natural interfaces have obvious shear peaks, while regular interfaces have no significant peaks. When the proportion of asperity width is less than 35%, the curved interface exhibits the highest shear strength, followed by the serrated interface and then the rectangular interface. When the proportion of asperity width exceeds 35%, the serrated interface shows the highest shear strength, followed by the curved interfaces and then the rectangular interface. Additionally, as the asperity width increases, the shear strength gradually increases. (2) Interface cohesion decreases in the order: serrated>arc-shaped>rectangular, whereas the internal friction angle decreases in the order: rectangular>serrated>arc-shaped. (3) During shear process, two shear planes form at the interface of a protruding body: a primary shear plane at the soil-rock interface and a secondary shear plane within the protrusion. The secondary shear plane primarily accounts for the differences in shear behavior of interfaces with different shapes.

Key words: soil-rock interface, shear strength, geometric morphology, failure mechanism