Uncertainty quantification of the bond stress : displacement relationship of shoring anchors in different geologic units.

Abstract

The design of anchored wall systems in shoring applications is generally governed by the bond strength between the grout and the surrounding soil-rock in the grouted bond zone. Published work on the reliability of anchored retaining systems focuses on ultimate limit state considerations to ensure a target level of safety-reliability against pullout of the anchor in the bonded zone at the grout-soil interface. These studies do not shed light on the variability of the bond strength at different levels of anchor slip (deformation) at the grout-soil interface. The primary objective of this paper is to quantify the uncertainty in the bond strength that is mobilized at target values of anchor slip to aid the serviceability limit state design of anchored wall systems. To achieve this objective, a database of actual shoring anchor tests from real projects that were executed in several sites around Beirut is assembled and analyzed to quantify the uncertainty in the mobilized bond strength at target levels of anchor deformation. The tests are categorized based on three different geologic units (Limestone, Marls, and Clays) that are common to many geologic settings in the world. The bond stress – displacement relationship is modeled with a hyperbolic model and the statistics of the model are derived from the assembled database and classified based on the geologic units analyzed. The secondary objective of this research is to show the effect of this uncertainty on a real anchored retaining wall example to reflect it on the reliability-based design of this example.