Which concept describes the ratio between the volume of voids and the volume of the soil mass?

The concept that accurately describes the ratio between the volume of voids and the volume of the soil mass is porosity. Porosity is a vital property in geotechnical engineering as it indicates how much of a soil sample is made up of void spaces, which can influence water drainage, soil stability, and overall behavior under load.

Porosity is calculated by dividing the volume of voids (the spaces between the soil particles) by the total volume of the soil sample, including both solids and voids. It serves as a critical factor in understanding the soil's ability to hold water or air, ultimately impacting various engineering applications, such as foundation design and groundwater management.

Moisture content measures the amount of water in a soil relative to its dry weight, while pore water pressure pertains to the pressure exerted by water within the soil's pores. Degree of saturation indicates how full the voids are with water but does not specifically represent the ratio of void volume to total volume. Each of these terms relates to soil behavior but does not specifically define the volume of voids against the entire volume as porosity does.