Unconfined interfacial friction of Geosynthetic Cementitious Composite Mats

Abstract

Geosynthetic Cementitious Composite Mats (GCCMs) are flexible, cementitious material-filled geosynthetics that harden on hydration to form thin concrete layers and are primarily used for surface erosion protection applications. When installing GCCMs on steep slopes and channels, the interfacial friction between the GCCM and the substrate must be understood to determine if anchoring is required to secure the material in place. Determining interface shear resistance using test methods such as ASTM D5321 require a shear box and confining load acting on the soil/GCCM, which may not accurately represent GCCM resistance, as when installed there is typically no confining load other than GCCM self-weight and water. To provide a more detailed understanding of ‘unconfined’ interfacial friction properties of GCCMs, the authors created a tilt table which could be filled with different substrates and inclined to record the angle of GCCM specimen slip on the substrate surface. This paper reviews the tilt table testing on two common GCCMs with different backing layers (PVC and LLDPE), tested on a number of substrates that are typically lined in GCCMs. Both the interfacial friction angle and adhesion are determined, with discussion on the relationship between adhesion and surcharge for some substrate types.