Mechanics of the Interface Interaction between Hemp Fibers and Compacted Clay

Abstract

A drive is currently underway in the construction industry to promote the use of in situ soils (including clays) that are reinforced with natural fibers. This effort is primarily driven by sustainability considerations and concerns. Understanding of the interface resistance between natural fibers and clays is critical for reliably predicting the response of structures that are built on, or with, fiber-reinforced clays. The objective of this paper was to investigate the interface shear strength between natural hemp fibers and clay through interface direct shear and single fiber pullout tests. The parameters that were varied are the compaction water content and the drainage condition at the interface. The results indicated that the interface shear strength parameters are significantly affected by the test mechanism and drainage conditions. For compacted fiber-reinforced clay systems that are governed by short-term stability conditions, interface interaction coefficients may be best quantified using fast single fiber pullout tests. For systems that are governed by long-term stability, the drained interface friction coefficient could be estimated using small-scale direct shear or single fiber pullout tests. Hemp fibers are relatively efficient at mobilizing the shear strength of the clay, with interface interaction coefficients that could approach unity. © 2019 American Society of Civil Engineers.