What happens to the dry density of soil when the water content increases during compaction?

When the water content of soil increases during compaction, the behavior of dry density can be understood in the context of soil mechanics. Initially, as water is added, it acts as a lubricant, allowing soil particles to move closer together, which can lead to an increase in dry density. This process continues up to a certain optimal water content. At this optimal point, the arrangement of soil particles is maximized for density due to sufficient moisture aiding in compaction without creating excessive pore pressure or reducing air voids too much.

However, once the water content surpasses this optimal level, the dry density typically no longer increases. This phenomenon occurs because additional water starts to lubricate the soil particles excessively, which can lead to a decrease in effective stress and a reduction in the ability to compact the soil further. Therefore, the assertion that the dry density becomes denser until a certain point accurately reflects the compaction behavior of soils with varying moisture content, aligning with the principles of soil compaction and mechanics.