Soil nailing is an in-place reinforcement of the soil/rock that utilizes steel tendons grouted into drilled holes to create a stable block. Shotcrete, reinforced with wire mesh and/or reinforcing steel, is applied to the face of the excavation to secure the soil between the nails. Soil nailing is installed from the top down as an excavation is made in 4 to 6-foot lifts.
Soil nailing is used for the temporary support of excavations, construction of permanent retaining walls, and for the control of landslides. Schnabel has successfully constructed soil nail walls in stiff clays and silts, some coarse grain soils, mixed soils with rock and weathered rock. Soil nailing is not recommended in cohesionless soil, organic soil or cuts below the water table.
Soil nail walls are usually built with smaller, easily mobilized equipment and without extensive steel fabrication. This minimizes the start-up time and makes soil nailing the best application for congested sites. Soil nailing can also used where there are overhead restrictions, such as bridge abutments and power lines, as there are no vertical elements to install. Soil nails are typically shorter than tiebacks for the same height of wall and thus may be preferable where there limited right-of-ways or property lines. In the proper soil and groundwater conditions, soil nail walls can be constructed faster and more economically than other retaining wall systems.