What does "degree of saturation" indicate in soil?

The degree of saturation in soil is a measure that indicates how much of the void space in the soil is filled with water. It is expressed as a ratio of the volume of water present in the soil's pores to the total volume of voids (the spaces between soil particles). This understanding is critical in evaluating the soil's behavior under various conditions, such as during construction or when analyzing groundwater movement. When the degree of saturation is expressed as a percentage, it provides insight into the soil's moisture content and helps predict how the soil will respond to loading, drainage, and changes in environmental conditions.

In contrast, measuring the proportion of liquid water to total soil weight relates to moisture content rather than saturation. The ratio of saturated soil to total soil volume does not accurately capture the dynamics of pore spaces and may lead to confusion with concepts like volumetric water content. Similarly, the proportion of solid material to voids describes the soil's density and structure but does not directly address how water fills those voids. Thus, understanding the degree of saturation specifically highlights the relationship between water and pore spaces, which is essential in geotechnical engineering and soil testing.