Soil Nailing is an earth retention technique that can be used as a remedial measure to treat unstable natural soil slopes, or as a technique to allow the safe over-steepening of new or existing soil slopes. The technique involves using grouted tension-resisting steel elements (nails) that can be designed for either temporary or permanent support. The walls are typically constructed from top down. Generally, 3 to 6 feet of soil is removed from the top of the intended excavation. Near-horizontal holes are drill into the exposed face at an average of 3 to 6 foot centers. Tension-resisting steel bars are put into the holes and grouted. A drainage system is set up on the exposed face, followed by the application of reinforced shotcrete (pneumatically applied concrete) facing. Compact face panels have also been used as an alternative to shotcrete. Bearing plates are then attached to the heads of the Soil Nails. The soil at the base of the first stage is then extracted to a depth of about 3 to 6 feet. The installment process is recurring until the design wall depth is reached. The completed Soil Nails create a zone of reinforced ground.
Soil Nailing equipment is small enough that is can effortlessly negotiate controlled access. For current steep slopes, such as existing retaining walls or bluffs, the Soil Nails can be installed from crane suspended working platforms. Soil Nails may also be established directly below existing structures adjacent to excavations. Attention should be taken when applying the system underneath an existing structure.
Soil Nailing may also be used to maintain retaining walls or existing fill slopes (embankments and levees), provide earth retention for excavations for buildings, plants, parking structures, deep cuts, and tunnels.