Field Compaction

It is difficult to compact all of the soil that is placed on a construction site at once. The thicker the layer, the less effect compaction has on the soil at the bottom of the layer. Soil is typically placed in layers and each layer is compacted. The layers start out at about 8" in depth and once compact it is about 6" in depth.

If the weather is warm and sunny, it is common practice to have a water truck sprinkle the soil with water. The soil is then mixed with the water using a disk plow. A disk plow will be shown and explained further in the next section.

Likewise, if the soil is too wet, a disk plow can be used to expose wet parts of the soil that are under the surface. This helps the soil to dry faster.

After each layer is compacted, it is good practice to 'rough up' the top of the smooth layer so that it bonds to the next layer of soil. Depending on the size of the area to be compacted, tampers and rollers are used.

POINTS TO REMEMBER:

• normally soil is compacted in layers
• usually each layer starts as 8" or 200mm of loose material which is then compacted to 6" or 150mm
• if the soil is too dry, water can be added with a water truck and mixed into the soil by disk plowing
• if the soil is too wet, moisture can be reduced by aeration, i.e. spreading it out, disk plowing to constantly turn out wet soil, and allowing to dry
• the surface of each layer should be 'roughed up' by disk plowing or scraping to provide bonding between the layers
• work is usually done by tampers and rollers
• tampers and rollers usually achieve their maximum compaction withing 6 - 10 complete passes over the compaction area