Multi-scale behavior at geomaterial interfaces

The design of interface elements in geotechnical engineering traditionally involves empiricism and lacks a solid fundamental underpinning based on the controlling mechanisms. These design shortcomings exist due to deficiencies in the fundamental understanding of geotechnical interface behaviors and the lack of test methods and devices available to directly measure interface properties in situ. The current work strives to improve the state of geotechnical knowledge and design with regard to interface behavior through fundamental laboratory studies and the development and use of a new in situ testing device. The current investigations are focused across a range of scales from micromechanical interactions to full scale field implementation. A series of laboratory investigations at the micromechanical level have been performed, specifically aimed at investigating the mechanisms controlling granular interactions against conventional and textured friction sleeves, and hook and loop type interactions present within textured geomembrane - geotextile systems. Additionally, a new in situ testing device has been designed and developed, the Multi Piezo Friction Attachment (MPFA), to allow for the characterization of geotechnical interface properties in situ within the context of an effective stress framework. The MPFA simultaneously provides four independent measures of interface friction (fa1, fa2, fa3, and fa4) and five independent measures of dynamic pore pressure along the shaft (ua0, ua1, ua2, u a3, and ua4) in addition to the conventional cone penetrometer measurements (qt, f s, and u2). Subsequent analysis regarding the implementation of the MPFA has proven the concept of directly characterizing interface behavior in situ as a function of surface roughness to be viable and effective across a range of geologic conditions. In addition to conventional test procedures, the multi friction attachments have been shown to be effective tools for use in a number of non-standard procedures, including: inclined penetration, variable rate penetration, small and large scale cycling, extraction monitoring, and for use in model pile investigations.