Experimental analysis of friction between sand and reinforcing elements using ring simple shear tests

Behavior of interfaces between soils and reinforcing elements plays a key role in the design and analysis of civil engineering structures, such as reinforced backfills or soil nailed structures. In this paper, we present a new laboratory device, the ring simple shear apparatus, especially designed for studying and measuring friction between sand and reinforcing elements. The principle of the apparatus is to revolve a rigid steel cylinder (modeling the reinforcement) in an annular sample of soil. The results presented herein are obtained with samples of Hostun sand (Dso=0.36 mm) or Hostun gravel (Dso=3 mm). The cylinder used have smooth or rough surfaces. The results show that the main factors which affect the friction and its mobilization are the nature of the surface, the nature and the density of the soil and the overburden pressure. Results of cyclic test show the degradation of the mobilized friction with the number of cycles.