Soil as a three-phase System

Soil deposits consist of the soil particles and the void space between the particles. Soil mass is generally referred to as three-phase system because it consists of solid particles, liquid, and gas. For many civil engineering purposes, the liquid may be considered to be water and the gas as air (Figure 1 and 2) with the exception geoenvironmental, and oil and gas applications. A saturated soil may be assumed to have only two of these phases, as voids are completely saturated with water (Figure 3).

Figure 1: Soil Mass

Figure 2: Three Phase Diagram

Figure 3: Fully Saturated Soil