Role of Initial State, Material Properties, and Confinement Condition on Local and Global Soil-Structure Interface Behavior during Cyclic Shear

Accurate prediction of the load transfer response of a geosystem requires an understanding of the micromechanical, or local, behavior of individual particles at the soil-structure interface. The difficulty in predicting local interface behavior is inhibited by a multitude of influential factors, including material properties, state parameters, and confinement conditions. While significant efforts have been made to investigate how load transfer occurs within the soil adjacent to the structural interface surface during monotonic shearing, there is a relative lack of local behavior studies focused on cyclic shearing and the resulting postcyclic monotonic response. This study presents the results of an investigation quantifying the localized soil-structure interface evolution during cyclic shearing using a modified direct interface shear box. Parameters investigated include relative density (initial void ratio), particle angularity, particle hardness, surface roughness, normal stress, and normal stiffness. Particle image velocimetry, a local nonintrusive measurement technique, is used to measure the local 2D particle displacement and interparticle strain distributions within the test specimens. The work extends a previous study focused on monotonic shearing using the same material properties and confinement conditions and further illustrates differences observed in the localized shear strain and volumetric strain zones adjacent to the structural surface. Insights provided by the detailed presentation of local data are linked to the global response to explain differences in precyclic monotonic and postcyclic monotonic behavior. The insights can be used to further understand the micromechanical response of sand interfaces for use in geotechnical design.