1.2 DEFINITIONS OF KEY TERMS
In this section, we define some important terms that help us understand the building blocks of soils. Each term explains a key part of what makes up the earth’s surface materials.
Minerals
Minerals are the basic chemical elements found in rocks. They form the natural ingredients that, when combined, make up the rocks and soils.
Rocks
Rocks are hard masses that are formed when minerals stick together. Think of them as the “solid blocks” that nature creates.
Soils
Soils are the materials that result from the weathering (breaking down) of rocks. They contain a mix of minerals, organic matter, and water, which together create the ground we walk on.
Effective Particle Size (D10)
This is the particle diameter at the 10th percentile, meaning that 10% of the soil particles are smaller than this size. It is a useful way to gauge the smallest grains in a soil sample.
Average Particle Diameter (D50)
D50 represents the median particle diameter of the soil. In other words, it is the size at which half of the soil particles are smaller and the other half are larger.
Uniformity Coefficient (Cu)
The uniformity coefficient is a number that tells us how similar the soil particles are in size. A high Cu means that most of the particles are close in size.
Coefficient of Curvature (CC)
Also known as the coefficient of gradation or coefficient of concavity, the CC measures the shape of the particle distribution curve. This helps in understanding how the particles are spread out in different sizes.
