Interface friction is one of the primary mechanisms relied upon in geotechnical engineering for load transfer. For example, the friction mechanism is utilized as the design basis in systems including deep foundations, tie-back walls, and geogrid reinforced walls. It must also be accounted for where it can influence the construction of geotechnical systems including tunneling and trenchless excavation. Recently, the counterface material surface roughness and hardness have been identified as primary factors which affect interface strength. It has been shown that a change in the counterface surface roughness alone can more than double the interface strength. Similarly, the counterface hardness has been shown to significantly influence the interface mechanisms and strength. Given the significant effect of these two factors on interface strength, they must be accounted for in geotechnical practice. To this end, a series of laboratory tests were performed on geotechnical construction materials in which hardness and surface roughness measurements were performed to identify typical values. Interface shear tests performed with these materials and a uniform sub-rounded sand allow for the effect of surface roughness and hardness on the interface mechanisms and both peak and residual friction values to be evaluated.
In geotechnical engineering, the interface strength between man-made geomaterials and soils is one of the most prominent and significant mechanisms that govern the performance of a structure. Interface mechanisms are essential to the performance of many geotechnical applications including friction piles, micro-tunneling, and reinforced earth systems as directly reflected in design calculations. The interface mechanism is also present in other geotechnical applications where it plays a secondary role in the performance and is not directly accounted for in design methods. Additionally, there are laboratory and field soil tests in which the results are significantly influenced by the conditions at an interface.