A Study of applicability of different facing types in soil nailing

Abstract

Soil nailing has been used in Sri Lanka lately, in a wide range of infrastructure projects, as a cost-effective stabilization technique that can be implemented quickly. However, detailed designs with rigor, for nailhead/ facing are not often carried out in the local practice. Full face shotcrete, grid beams connecting nail heads, isolated nail heads (Pillows), and combinations of all these facings types used in the local practice. When the full face shotcreting is not used vegetation is used as a surface protection cover in between the nail heads with the help of a geotextile and nail heads are combined with a wire mesh of specified tensile strength. The mesh is expected to provide stability against any local shallow failures. The versions without full-face shotcrete blend nicely with the natural environment and have gained greater acceptance. In this research design guidelines for different facing types available in published literature are critically reviewed to assess the suitability under high rainfall intensities in local residual soil formations. A number of sites rectified with soil nailing with different types of facing have now experienced few seasons of rainfall and their performance is assessed. The cost-effectiveness and construction difficulties are also reviewed. Based on these factors some guidelines are developed to decide on the most appropriate type of facing depending on the prevailing local conditions.