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ground improvement

Ground Improvement: Introduction and Common Types

Various techniques and principles are employed during construction, and ground improvement is one of them.

The ground improvement technique is used when the behaviour of the underlying soil and/or the fill mass does not meet the required design criteria.

This technique is carried out at any time and any location once construction is completed. The purpose of this post is to introduce five common ground improvement techniques for your engineering projects.

 

5 Techniques Used for Ground Improvement

The following are ground improvement techniques:

 

1. Prefabricated Vertical Drains (PVD)

Prefabricated vertical drains are prefabricated geotextile filter-wrapped plastic strips with molded channels.

Also known as band drains or Wick Drains, prefabricated vertical drains serve as drainage paths to take pore water out of soft compressible soils that consolidate faster under a constant surcharge load.

Benefits

Common Uses

  • To accelerate drainage
  • Applicable in soft, saturated fine-grain soils, such as peat, dredge fills, silts, sludges, clays, and mine tailings, with large pore capacity and normally saturated
  • Consolidate leach pads and tailing ponds
 

2. Dynamic Compaction (DC)

Dynamic compaction is a ground improvement technique that involves the controlled impact of a crane hoisted weight, (usually around 10-30 tonnes), falling in a pre-determined grid pattern. DC aims to improve loose, granular soils and fills. 

Benefits

  • Capable of compacting a wide variety of weak soils
  • Dynamic compaction leaves a site clean and debris-free
  • Construction can commence immediately after the dynamic compaction is completed
  • Reduced settlement
  • Can avoid the removal of compressible, contaminated fills
  • Increased bearing capacity
  • Treated granular soils and fills have increased stiffness, density, and friction angle
  • Can greatly improve soil conditions on marginal sites to extent that deep excavation or piling isn’t needed during the construction of shallow foundations

Common uses

  • Reduces settlement
  • Increase bearing capacity
  • Decrease sinkhole potential
  • Mitigate liquefaction

 

3. Vibro Compaction (VC)

Vibro compaction is an old ground improvement method that uses a downhole vibrator to densify clean, cohesionless granular soils.

Benefits

  • Can be adjusted to different types of soil conditions and foundation requirements
  • Noise levels are negligible during production
  • Can be carried out to almost any depth
  • Relatively quick execution so subsequent structural works can follow very quickly
  • VC uses natural materials which makes it environmentally friendly
  • Maintains original site elevation where backfill is used
  • This versatile ground-improvement method assures quality
  • Offers an economical solution for ground improvement

Common uses

  • Reduce foundation settlement
  • Increasing stiffness
  • Increase bearing capacity, as such, allows a reduction in footing size
  • Highly effective for compacting reclaimed lands
  • Reduce permeability
  • Increase slope stability
  • Permit construction infills
  • Prevent the earthquake-induced lateral spreading
  • Mitigate liquefaction potential under a seismic event
  • For increasing shear strength

 

4. Deep Soil Mixing

Deep soil mixing involves two methods: wet and dry method.

a. Wet Method

The deep soil mixing wet method improves the characteristics of weak soils by mechanically mixing them with cementitious binder slurry.

Benefits

  • Quiet and vibration-free
  • The use of readily-available materials make it environmentally friendly
  • Very economical
  • Flexible in application
  • Reduces construction time
  • Operations can be done at low temperatures
  • Almost no spoil
  • Can replace more expensive deep foundation methods

Common uses

  • Retention systems and excavation support
  • Road and railway embankments
  • Bridge supports and abutments, wind-turbine foundations
  • Slope stabilization
  • Support of pad, slab, and strip foundations

 

b. Dry method

The deep soil mixing dry method improves peats, soft, high moisture clays, and other weak soils, by mechanically mixing them with the dry cementitious binder.

Benefits

  • Flexible in application
  • Environmentally-friendly as it uses readily available materials
  • Almost no spoil
  • Quiet and vibration-free
  • Reduces construction time
  • Operations can be done at low temperatures
  • Can replace more expensive deep foundation methods
  • Economical

Common uses

  • Mitigate liquefaction
  • Applicable in high-moisture content soils and (oftentimes) in high groundwater conditions, to allow chemical reaction of the soil and groundwater with stabilizing binders injected in dry form
  • Increase bearing capacity
  • Fixate contaminants in situ materials
  • Increase global stability
  • Decrease settlement

 

5. Rigid Inclusions (RI)

Rigid inclusion is a ground improvement technique that uses high-deformation modulus columns constructed through compressible soils to increase bearing capacity and reduce settlement.

Benefits

  • Can be used in all construction sectors and applied for most soil types and structures
  • Allows the use of shallow foundations to support structure on compressible soils
  • Minimal spoil
  • Increases the bearing capacity of weak soils, especially for high loads
  • Highly efficient in reducing settlements (reduction factor ranges from 3 – 8)

Common uses

  • Embankments for road and rail
  • Industrial flooring
  • Warehouses
  • Public buildings
  • Commercial and industrial buildings
  • Residential buildings
  • Wind turbines
  • Terminals and storage tanks

 

Conclusion

Ground improvement plays a vital role in ensuring that the soil and subsoil of a land reclamation project are safe and secure for construction purposes.

Prefabricated vertical drain contractors use this technique because it is flexible and durable, sufficient enough to bear the capacity of any foundation irrespective of the slopes.

 

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