What is Soil Nailing?
Soil nailing is a fundamental concept of reinforcement of existing ground conditions (natural slopes/cuts) by inserting closely spaced passive inclusions called ‘nails’. These nails are driven directly into the ground or grouted into drilled holes (to increase the in–situ soil shear strength and provide stability). The soil nailing technique is used to provide reinforcement to both in-situ natural and steep cut slopes. Soil nailing provides the required support for buildings in the vicinity of an unstable area which may be sensitive to deformation. Soil nailing is used to provide stability for temporary constructions or permanent retaining structures with appropriate measures to reduce ground movements. In a soil-nailed retaining wall, the properties and material behavior of the following three components significantly affects the performance of the structure; the native soil, the reinforcement (nails), and the facing elements and their mutual interactions.
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All soil nails within a cross section are usually located above the groundwater table, however, if the soil nails are below the groundwater table it must be proven that the groundwater does not adversely affect the face of the excavation, the bond strength of the interface between the grout and the surrounding ground, or the long-term integrity of the soil nails (e.g., the chemical characteristics of the ground do not promote corrosion).

Soil nails involve the rigid reinforcing of a soil mass. These nails can resist tension, shear forces and bending moments which are imposed by a slope's movement. The nail inside the soil should be fully grouted, usually non-prestressed, and nails should be relatively closely spaced. No force will act on a soil nail system until a soil mass failure. Usually soil nails involve a more simplistic installation technique than soil anchors and are easier to construct.

Favorable Soils: Stiff to hard fine–grained soils, dense to very dense granular soils with some apparent cohesion, weathered rock with no weakness planes, glacial soils, etc.

Unfavorable Soils: Dry, poorly graded cohesion less soils, soils with high groundwater, soils with cobbles and boulders, soft to very soft fine-grained soils, organic soils, etc.