Evaluating the Effects of Asperity Height on Shear Strength of Cohesive Soil-Structure Interface Subjected to Monotonic and Cyclic Axial Loading

The load-carrying capacity of geotechnical systems (e.g., foundations supporting offshore wind turbines) subjected to static and/or cyclic axial loading could be enhanced using engineered or idealized textured surfaces (or surface elements). The use of surface elements may allow for the development of passive wedges during axial loading, which result in an additional interface resistance to the total load-carrying capacity. To investigate the effects of surface pattern and asperity height on the static and post-cyclic interface shear response, the cyclic interface shear test (CIST) device, which was developed by the research team, was used. To achieve this, a smooth plate representing the surface condition of commonly used steel piles and four engineered textured plates (i.e., rough plates) of different level of roughness (i.e., asperity height of 0.35, 0.65, 1.25, and 1.75 mm) were 3D printed, and then the soil-plate interface was subjected to monotonic and cyclic axial loading. The interface shear tests were performed in a normally consolidated sand-kaolinite mixture. In this paper, the experimental setup (i.e., CIST), sample preparation, and results of a series of static and displacement-controlled cyclic interface shear tests on smooth and textured (rough) plates are summarized and compared to the static and post-cyclic soil-smooth shear strength (no surface elements). For static tests, the interface shear strength increased with asperity height, and this increase ranged from ~55% to 105% of the soil-smooth interface shear strength. Similarly, the post-cyclic interface shear strength increased with asperity height, and this increase ranged from ~167% to 266% of the soil-smooth interface shear strength. The preliminary test results included in this paper also show that the interface shear resistance of surfaces with structured elements is controlled by asperity height (h) and asperity spacing to height ratio (Sc/h ratio).