Dynamic pull-out tests to characterize the earthquake behavior of soil-nailed walls

抄録

Soil-nailed walls are retaining structures often used for their economic efficiency and ease of implementation. Moreover, post-earthquake surveys, and after the Loma Prieta earthquake, have demonstrated their exceptional seismic resilience, leading researchers to further investigate their seismic behavior and design. Among possible explanations, the repeated dynamic mobilization of friction at the interface between the soil and the nails is considered to be a major source of energy dissipation during an earthquake. Nevertheless, overdesigning soil-nailed walls to resist earthquakes increases their stiffness and, consequently, the amount of seismic energy transmitted to the supported structures. Inspecting an improvement of these walls seismic geotechnical design, the local dynamic soil-nail interface behavior appears to be of major concern. However, in the literature, only few studies have so far been devoted to this topic. With that specific purpose in mind, the RRO laboratory, Gustave Eiffel University, has recently designed and developed a new impulsive pullout tests device. This device, presented in this paper, allows applying at the nail’s head, about a static tension force, a series of dynamic load pulses up to 50% of the applied force at specified frequencies ranging from 0.1 to 5 Hz. In addition to the usual tension force and displacement measurements at the head of the nail, micro-deformations along entire length of the steel bar are observed at a millimeter longitudinal resolution based on optical fiber technique. The new device and the high-resolution monitoring of strain along the bar allows to investigate the local seismic behavior of the soil-nail interface, in order to propose a model to account for this behavior in soil-nailed walls design methods.