Ground improvement techniques

[edit] Introduction

There are a number of ground improvement or ground modification techniques that can be used to stabilise or improve the condition of an area of ground before construction work takes place. This may be necessary to improve or modify the ground shear strength, stiffness, permeability, and so on.

Some of the most techniques include:

[edit] Grouting

Grouting in civil engineering refers to the injection of pumpable materials into a soil or rock formation to change its physical characteristics. It is one of the ways in which ground water can be controlled during civil engineering works. Grouting is suitable where soil permeability would create a heavy demand on pumping or where ground conditions mean it may be economically inefficient to bore wells.

Jet grouting uses high velocity fluid jets to construct cemented soil and is commonly used to underpin foundations and provide excavation support.

Chemical grouting uses a low viscosity, non-particulate grout to permeate pore spaces in granular soils and hardens to create a cemented mass.

For more information, see Grouting in civil engineering.

[edit] Soil mixing

Soil mixing improves soft clays, peats and other weak soils with a high moisture content. It involves mechanically mixing the wet soils with a dry cementitious binder to create soilcrete. This helps increase bearing capacity and decrease settlement.

[edit] Soil compaction

Soil compaction produces an increase in soil density and a decrease in air volume without producing a decrease in water content. It can improve shear strength, stiffness, bearing capacity and stability, reducing settlement and frost heave. This may be necessary in the construction of bases for highways, embankments and so on, or to create a suitable level base for the construction of a building. Existing soil can be compacted, or layers of new soil can be compacted, taking a site to the required level.

For more information see: Soil compaction.

[edit] Vibro-replacement

Vibro-replacement works by using a crane-suspended downhole vibrator to construct stone columns through weak soils, improving their load-bearing and settlement capacities. Another term that can be used for this technique is vibro stone columns (VSC).

For more information, see Vibro-replacement.

[edit] Geotextiles

Geotextiles are typically made using synthetic fibres such as polyester or polypropylene which create a flexible and porous fabric capable of providing strength and stability. Geotextiles have the ability to reinforce, protect, filter, drain and separate, and many applications use them alongside soil, placed at the tension surface for strength purposes.

For more information, see Geotextiles.

[edit] Cement/lime stabilisation

This involves the addition of a binder product such as hydrated lime or quicklime to soil which reduces moisture and improves stability.

[edit] Related articles on Designing Buildings Wiki

• Bearing capacity.
• Biosolids.
• Building on fill.
• Enabling works.
• Excavation.
• Geophysical survey.
• Geotechnical engineering.
• Ground conditions.
• Ground heave.
• Ground investigation.
• Groundworks.
• Insitu testing of soils.
• Settlement.
• Soil compaction.
• Soil report.
• Soil treatment.
• Trial pit.
• Types of soil.