No, you generally cannot effectively compact saturated soil.
Here's why:
Saturated soil is soil where the pore spaces between soil particles are completely filled with water. This condition prevents effective compaction for several reasons:
-
Incompressibility of Water: Water is essentially incompressible. When you apply compactive force to saturated soil, the water resists being compressed.
-
Reduced Friction: The presence of excess water reduces friction between soil particles, preventing them from interlocking and achieving a denser state. The particles essentially "float" in the water.
-
Pumping: Compaction efforts on saturated soil can lead to a phenomenon called "pumping." As the compactor applies pressure, the water is forced upward, carrying fine soil particles with it. This creates a muddy surface and ultimately results in a weaker, less stable soil structure, preventing true compaction.
Instead of compacting saturated soil directly, you typically need to:
- Remove excess water: This can be achieved through drainage techniques such as installing drainage systems (e.g., French drains, ditches), using well points, or allowing the soil to dry naturally through evaporation.
- Stabilize the soil: After draining, the soil may still need stabilization. Soil stabilization techniques can include adding amendments like lime, cement, or fly ash to improve its strength and workability for compaction.
The key to successful soil compaction lies in achieving the optimum moisture content. This is the moisture level that allows for maximum density upon compaction. Too little moisture, and the soil particles won't bind together effectively. Too much moisture (as in saturated soil), and the water interferes with particle interaction.
In summary, attempting to compact saturated soil is unproductive and can even be detrimental. Proper drainage and potentially soil stabilization are necessary to create a compactable base.
