The Influence of Surface Characteristics on Cohesive Soils–Structure Interface Monotonic Shear Response

ABSTRACT The response of geo-structures subjected to static axial loading, cyclic axial loading, or both depends on the shear response at the soil–structure interface. In this research study, the cyclic interface shear test system, an automated interface testing device that was developed by the research team, was used to perform monotonic interface shear tests to fundamentally understand the influence of surface characteristics, such as height of asperity (h) and its spacing (Sc), on the shear response of cohesive soil–structure interface. The test setup allows for the direct measurements of the shear force and shear displacement curves, in addition to the soil volume change at the interface. In this paper, normally consolidated cohesive soil was prepared in the laboratory and interface shear tests were conducted on surfaces with asperity heights (h) ranging from 0 (smooth, no surface elements) to 1.75 mm, and on surfaces with center-to-center asperity spacing (Sc) ranging from 0 (smooth, no surface elements) to 25.4 mm. The shear resistance increased with height (h) when the soil-plates interface sheared under static axial shearing. Furthermore, it is concluded that the interface shear resistance is controlled by the spacing-to-height (Sc/h) ratio. According to the test findings presented in this research study, a Sc/h ratio ranging between 7 to 9 mobilizes the maximum interface shear resistance for the tested cohesive soil.