Soil nailing : Behavior under seismic loading of the soil-nail interface

Overview & Synopsis

Soil nailing has been used since the early 1970s as an excavation retaining technique. Its efficiency has led to widespread adoption. The method consists of reinforcing the soilmass with passive inclusions (generally steel bars), which, upon excavation, mobilize friction along the soil–nail interface due to soil mass displacements, thereby securing the stability of the structure. The interaction along this interface is therefore a keyfactor in design and has been extensively investigated under static loading conditions. Post-earthquake surveys have shown that soil-nailed walls often demonstrate remarkable resilience under seismic loading. This has motivated further research into their dynamic behavior. Various approaches have been adopted, including shaking-tabletests, centrifuge modeling, and numerical simulations, accounting for factors such assoil mechanical properties, input motion characteristics, and site effects. While most studies have focused on the overall stability of the structure, the local interaction along the soil–nail interface — particularly friction — has not been studied in sufficient detail. The properties of this interface, including its ultimate strength and stiffness, should be considered at the local scale. In this context, the present thesis aims to improve the understanding of the local behavior of the soil–nail interface under dynamic loading conditions, with particular attention to the evolution of interface properties during dynamic excitation. Field pull-out tests were conducted under varying site conditions and loading parameters,with excitation frequencies ranging from 0.1 to 5 Hz. Local performance along the interface was monitored using optical fiber measurements. The experimental results revealed that the loading rate influences interface stiffness, in addition to the effect of overburden pressure on interface rigidity. Complementary laboratory tests under controlled conditions were also performed to provide further insight into the effects of loading rate and overburden pressure, as observed in the field. These tests were carried out in a large pull-out box using dense sand specimens subjected to various overburden pressures