Testing and Modeling of Saturated Interfaces with Effect of Surface Roughness. I: Test Behavior

The response of structure-foundation systems subjected to static, cyclic, or dynamic load depends on the interaction between them. The behavior of such systems is strongly nonlinear and inelastic and is affected by factors such as the interface behavior, e.g., relative motions, pore water pressure, and surface roughness. This two-part paper presents new and unique constitutive modeling, testing, and validations for interface behavior affected by factors such as surface roughness, confining pressure, amplitude, and frequency of cyclic loading. The aim of this work is to gain an improved understanding of the mechanical behavior of saturated interfaces between structural and geologic materials subjected to cyclic loading with emphasis on the effect of surface roughness of structural material; this is important for safety and to improve analysis and design of geotechnical structures. Monotonic and cyclic simple shear experiments are conducted on Ottawa sand-steel interfaces under undrained conditions using the cyclic multidegree-of-freedom shear device (CYMDOF-P) with pore water pressure measurements. The effect of various parameters such as normal stress, surface roughness of steel, type of loading, and the amplitude and frequency of the applied displacement in cyclic loading are investigated in Part I. The constitutive modeling for the interfaces are presented in Part II.