What are the deep compaction techniques?

Deep compaction techniques are methods used to increase the density and strength of soil at significant depths below the ground surface. These techniques are widely applied in construction projects to improve the load-bearing capacity of soils, reduce settlement, and mitigate liquefaction risks in seismic areas. 

Here are the primary deep compaction techniques:

1. Vibrocompaction 

 Process : A vibroflot (vibrating probe) is inserted into granular soils, creating vibrations that rearrange soil particles into a denser configuration.

 Best For : Loose, granular soils with low silt and clay content.

 Applications : Ports, offshore structures, and large foundations.

2. Dynamic Compaction 

 Process : Heavy weights (10–40 tons) are repeatedly dropped from significant heights (10–30 meters) onto the ground surface, compacting the soil below.

 Best For : Granular and mixed soils; sometimes cohesive soils with predrainage.

 Applications : Industrial platforms, road embankments, and airport runways.

3. Deep Soil Mixing 

 Process : A drill mixes the soil with stabilizing agents (cement, lime) at depth to improve strength and reduce permeability.

 Best For : Weak, compressible soils, especially clays and silts.

 Applications : Retaining walls, foundation support, and liquefaction mitigation.

4. Stone Columns (Vibro Replacement) 

 Process : A vibrating probe creates vertical cavities, which are then filled with coarse gravel or crushed stone to create load-bearing columns.

 Best For : Loose sands, silts, and clays with moderate strength.

 Applications : Settlement control under structures, liquefaction prevention, and slope stabilization.

5. Compaction Grouting 

 Process : A thick grout is injected into the soil under pressure, displacing and compacting it.

 Best For : Loose sands, silts, and some clays.

 Applications : Foundation repair, void filling, and liquefaction control.

6. Preloading (Surcharge) with Vertical Drains 

 Process : The soil is subjected to preloading (via fill or a surcharge), often combined with vertical drains to expedite consolidation.

 Best For : Soft clays and silts with high water content.

 Applications : Settlement control for large-area fills like land reclamation.

7. Compacted Sand Piles 

 Process : Cylindrical holes are created and filled with compacted sand to improve soil bearing capacity and reduce settlement.

 Best For : Loose and weak soils.

 Applications : Foundation support in soft soil areas.

8. Electro-osmosis 

 Process : An electric current is passed through wet soils to remove water, increasing their strength and density.

 Best For : Fine-grained soils like clays and silts.

 Applications : Underground tunneling and excavation stabilization.

Each technique is selected based on the type of soil, depth of improvement required, and specific project requirements.