WHAT IS THE MEANING OF SOIL REINFORCEMENT? (JOB INTERVIEW QUESTION)

WHAT IS THE MEANING OF SOIL REINFORCEMENT?
Reinforcement of Soil can generally be subdivided into 2 categories:
A) -Reinforced Soils
B) -In-situ Reinforcement. Also termed as “soil nailing”.

Soil Reinforcement may be made with a number of materials:
1. Woven Geotextiles
2. Polymer Geogrids of Polyethylene (usually uniaxial) & polypropylene (usually biaxial)
3. Polyester and Fiberglass Geogrids (often knitted or stitched at junctions) and usually coated with a polymer such as polyethylene or PVC or with bitumen.
4. Steel Strips (the original “Reinforced EarthTM”)
5. Welded wire mesh.

Soil nailing technique:
Soil nailing is an in-situ reinforcement technique, was originally introduced in France in the 1970s. It can be described as an in-situ reinforcing of soil using an array of nails installed as passive inclusions in a grid. The construction begins with the excavation of a shallow cut (Fig) on the face of which wire mesh is laid followed by applying shotcrete to the face. When the latter is set, soil nails are drilled through the shotcrete and grouted, followed by 9 anchoring them to the wall. The sequence is repeated until the final depth is reached. The nail being rigid, unlike the reinforcing strip in reinforced earth, can resist some bending and shear in addition to axial tension. An innovative step is the use of screw nails which are installed by rotation (like screw piles), giving rise to enhanced friction at the soil-nail interface. (This is akin to increased bond in the case of deformed reinforcement bars.)

Soil nailing cannot replace all other methods of soil retention technically or economically. Notwithstanding the same, it has the following advantages:
1. It is not dependent on heavy equipment
2. It is economical where the geometry of the wall is complex and where space restrictions exist
3. Since nails are of low strength steel, the need for corrosion protection stands reduced
4. Construction can be carried out with little disturbance to the environment in terms of noise and vibration
Not Applicable:
Soil nailing is not practical in:
- Soft, plastic clays
- Organics/Peat
- Fills (rubble, cinder, ash, etc.)