Optimum Moisture Content (OMC) is defined as the moisture content at which what occurs?

• A. A maximum density is obtained for a given amount of compactive input energy
• B. Density is minimized under a fixed energy
• C. Density is independent of energy
• D. Soil becomes fully saturated

Answer: (A)

Optimum Moisture Content is the moisture level at which the soil achieves its maximum dry density for a given amount of compactive energy. Water acts as a lubricant, allowing particles to rearrange into a tighter packing as moisture increases from very dry conditions. At the peak, you get the densest arrangement possible with that energy input. If the soil is drier than this point, lack of lubrication limits densification; if it’s wetter than this point, excess water reduces effective stress and fills pores, reducing the achievable density. It’s not about becoming fully saturated—the criterion is the moisture content that yields the highest dry density under the specified compactive energy.