Soil Phase Relations, Types, Calculation & Its Application In Civil Engineering

In solid materials, phase relations refer to the different states or phases that a substance can exist in, depending on factors such as temperature and pressure.

The three main phases in solids are solid, liquid, and gas. However, in this particular context, we will focus on the phase relations within the solid phase.

Phase Relations in Solids

In solids, the atoms or molecules are closely packed together, forming a rigid and organized structure. The arrangement of these atoms or molecules determines the properties of the solid, such as its density, hardness, and electrical conductivity.

The behavior of solids can vary significantly based on the type of bonding between the atoms or molecules, such as metallic, ionic, or covalent bonding.

One important phase relation in solids is the phase transition between different crystalline structures. Crystals are characterized by their highly ordered arrangement of atoms or molecules in a repeating pattern. The specific arrangement of atoms in a crystal is known as its crystal lattice.

Different types of solids can have different crystal structures, such as cubic, tetragonal, orthorhombic, or hexagonal. Phase transitions in solids can occur when there is a change in temperature or pressure.

The most common phase transition in solids is the transition between different crystal structures, known as polymorphism. For example, carbon can exist in two different crystal structures: diamond and graphite. This phase transition occurs due to changes in temperature and pressure, resulting in the rearrangement of carbon atoms from a tetrahedral lattice in diamond to a layered structure in graphite.

Phase transitions in solids can also occur due to the addition or removal of impurities or defects in the crystal lattice. These impurities can disrupt the regular arrangement of atoms, leading to changes in the properties of the solid. For example, adding a small amount of impurities to a semiconductor crystal can change its electrical conductivity, making it useful for electronic devices.

Phase relations in solids are essential in understanding the behavior and properties of materials. They play a crucial role in various fields, such as materials science, chemistry, and engineering. By studying and manipulating the phase relations in solids, scientists and engineers can develop new materials with desired properties or improve the performance of existing materials.

With regards to civil engineering, let us look at the phase relationship in soil which is an important civil engineering property.

A soil mass generally contains:

• Solids
• Water
• Air

The combination of water and air gives rise to voids in the soil.

Total volume V is given as V = Vs + Vw + Va

Where:

Vs = Volume of solid

Vw = Volume of water

Va = Volume of air

Similarly, the corresponding weights are given as:

Wa = Weight of air (usually zero)

Ww = Weight of water

Ws = Weight of solids

W = Total weight

The total volume of voids = Vv = Vw + Va (i.e., volume occupied by water and air).