Soil nailing is an earth retention technique using grouted tension-resisting steel elements (nails) that can be design for permanent or temporary support. The walls are generally constructed from the top down. Typically, 3 to 6 feet of soil is excavated from the top of the planned excavation. Near-horizontal holes are drilled into the exposed face at typically 3 to 6 foot centers. Tension-resisting steel bars are inserted into the holes and grouted. A drainage system is installed on the exposed face, followed by the application of reinforced shotcrete facing. Precast face panels have also been used instead of shotcrete. Bearing plates are then fixed to the heads of the soil nails. The soil at the base of this first stage is then removed to a depth of about 3 to 6 feet. The installation process is repeated until the design wall depth is reached. The finished soil nails produce a zone of reinforced ground.
Soil nailing equipment is small enough that it can easily negotiate restricted access. For existing steep slopes, such as bluffs or existing retaining walls, the soil nails can be installed from crane-suspended working platforms. Soil nails can also be installed directly beneath existing structures adjacent to excavations. Care should be exercised when applying the system underneath an existing structure. Hayward Baker has used extensive 3D modeling to avoid conflicts between soil nails and other earth retention systems on complex projects that involve the use of multiple techniques, and to ensure the safety of buried utilities.
Soil nailing has been used to stabilize slopes and landslides, provide earth retention for excavations for buildings, plants, parking structures, tunnels, deep cuts, and repair existing retaining walls.
This technique is available in most areas through either Hayward Baker or sister Keller companies. Contact your local Hayward Baker office for more information on soil nailing.