Since its development in Europe in the early 1970s, soil nailing has become a widely accepted method of providing temporary and permanent earth support, underpinning and slope stabilization on many civil projects in the United States. In the early years, soil nailing was typically performed only on projects where specialty geotechnical contractors offered it as an alternate to other, conventional systems. More recently, soil nailing has been specified as the system of choice due to its overall acceptance and effectiveness. However, although the theoretical engineering aspects of soil nailing may be well understood, there is a far lesser degree of understanding, even within the geotechnical community, as to the site conditions – where, when and why – under which soil nailing should, and should not, be used. The purpose of this paper, therefore, is to offer experienced-based guidelines to owners, engineers, designers and general contractors trying to decide if soil nailing is the right system for their project. Typical soil nail details, procedures, design, monitoring and testing considerations, and case studies are presented as a tool to aid in making those decisions.
Soil nailing is an economical, top-down construction technique that increases the overall shear strength of unsupported soils in situ through the installation of closely spaced reinforcing bars into the soil/rock. Typically, a structural concrete facing is sprayed against the excavated earth face to connect the nails and reduce deterioration and sloughing. A common misconception is that this structural facing is the major element of the soil nail system. In fact, the nails do the work.
Soil nails are passive elements and, unlike tieback anchors, they are typically not mechanically pre-tensioned after installation. Rather, they become forced in tension when the soil they are supporting deforms laterally as the depth of the