Shear zone evolution of granular soils in contact with conventional and textured CPT friction sleeves

Interfaces, and the shearing of soil against them, play a crucial role in geotechnical engineering. As such, understanding the fundamental mechanisms of interface behavior, such as the size, shape, and extent of soil shear zones against geomaterial surfaces can lead to better understanding and design of geotechnical systems and testing methods. The current study presents a series of laboratory studies aimed at spatially quantifying shear zones created through soil-geomaterial interface shearing including mobilized interface strengths with a focus on CPT friction sleeve behavior. Parametric investigations of particle shape and size effects were carried out over a range of counterface surface roughness values. The results show that conventional smooth CPT friction sleeves induce solely particle sliding in coarse grained soils, while non-clogging textured friction sleeves can create a combination of particle shearing and sliding that can allow for direct interface measurements in-situ. By varying the amount of texture on an interface, the extent of particle shearing can be controlled, allowing for improved understanding and treatment of interfaces in geotechnical testing and design.