Large-scale Testing of High-Tensile Steel Meshes and Soil Nails for Ground Surface Support: Validation of Modelling Software

Roberto Luis Fonseca, Gonzalo Díaz Trillos, and Armin Roduner

Geobrugg Group, Switzerland

Abstract: The stability of newly cut or natural slopes is an important issue of geotechnical engineering. Regardless of the scale of the project, the design and the execution must assure maintenance-free and, more importantly, safe utilisation of the slope. Nowadays, a geotechnical engineer can choose from several different, available slope stabilisation methods. Nevertheless, one of the most frequently chosen methods is soil nailing in combination with flexible facing [1]. In this configuration, the soil nails are designed to stabilise deep-seated instabilities, while localised instabilities must be stabilised by the strong flexible facing, typically represented by high-tensile steel wire mesh. To assure proper slope stabilisation, the soil nails and the flexible facing must act as one integrated system. Such a system has been lately tested in large scale within this R&D project supported by the Swiss Institute for Technology and Innovation (CTI). The large-scale setup, widely described in Cała et al. (2013) [2], consisted of an inclinable large box (12 × 10 × 1.2 m), soil material, nails, high-tensile steel wire mesh, steel plates (linking nail heads and mesh), connection clips (linking two sheets of mesh) and boundary ropes. The entire setup was lifted on one side to imitate the slope inclination. While lifting the box up several measurements were taken (e.g., tension forces and bending in the nails or mesh displacement). In total 31 large-scale tests were conducted, at first to check the testing setup and later to test the interactions of the nails and high-tensile steel mesh, which were put together in different arrangement and configurations. The most important testing variables were soil material, nail pattern, type of steel wire mesh and connection plate. The main aim of this paper is to present the analysis of the performance of three meshes composed of 2, 3 and 4 mm diameter wire, tested in comparable conditions (the same soil conditions, nail pattern and connection plate). The purpose of this analysis was to show the distinction in bearing capacity and range of deformation of meshes produced from the same steel high quality but of different wire diameter. This analysis was also used for the purpose of validation of already existing dimensioning concept based on lab tests