Insights on rate effects on the dynamic pullout resistance of anchors of flexible barriers

Abstract

Existing research on the design of flexible barriers to arrest geohazards mainly focuses on the optimisation of the superstructure. Little attention has been given to the optimization of the foundation anchors used to transmit dynamic impact loading to the ground. In fact, design guidelines for foundation anchors for flexible barriers are based on quasi-static pullout theories even though field evidence suggests that the dynamic response of an anchor is fundamentally different. In this study, a new analytical model is proposed to predict the peak pullout resistance for anchors subjected to dynamic loading in saturated sand. A novel experimental apparatus was developed to evaluate the proposed analytical model. Dynamic effects are profound in saturated sand and less so in dry sand. Rate strengthening at the soil-anchor interface is governed by pore pressure change from dilation and soil damping. The proposed model is shown to give close predictions of the measured peak dynamic pullout resistance, which is up to three times those under quasi-static conditions. Findings imply that rate strengthening changes the critical failure mechanism of a foundation anchor from the soil-anchor interface for quasistatic loading to the potential rupturing of the steel tendon for dynamic loading.