HYBRID DESIGN APPROACH FOR ANCHORED WIRE MESH: TOWARDS A DISPLACEMENT-BASED DESIGN

Anchored (or pinned) wire mesh, commonly employed as passive stabilizing systems for potentially unstable slopes in granular soil or highly fragmented weak rock, are composite structures consisting of wire mesh, steel plates and reinforcing bars/ties. Their stabilizing action is determined by the complex interaction of such elements with the underlying unstable layer, depending on the geometry of the slope, the stabilizing intervention, mechanical properties of the soil and mesh, and the intensity and time variability of applied loads (especially environmental loads, e.g. seasonal water table variations). Standard design approaches are often based on an Ultimate Limit State hypothesis (ULS), assuming the full mobilization of both the ultimate soil resistance and the ultimate tensile force in the wire mesh. Such hypothesis can potentially lead to an unsafe design, especially when passive stabilizing systems are considered, since the stabilizing action is mobilized only upon the activation of soil displacement. In this study, based on recent advances in design methods for slope stabilizing systems, an advanced “hybrid” method is presented and demonstrated combining an ULS analysis of the unstable slope with a Serviceability Limit State analysis (SLS) for the wire mesh. This hybrid method allows the designer to easily and consistently estimate the affect of soil displacement on the factor of safety of the slope, thus proving the efficacy of the wire mesh to reduce soil displacement and allow the influence of both its strength and stiffness to be determined.