Module 04
Particle size, description and classification
Gravel to clay, grading curves and their D-values, and how a soil is described and classified — with its limits.
What this module covers
- Name the particle-size fractions and the coarse/fine division
- Read a grading curve and extract D10, D30 and D60
- Compute the uniformity and curvature coefficients and describe the gradation
- Explain plasticity and how fine soils are classified
- Recognise what classification does and does not tell you
Lessons
From boulders to clay platelets — and why the fines change everything.
Start lesson →Read the distribution, then judge whether a soil is well, poorly or gap graded.
Start lesson →How fine soils are classified, and why classification is only the start.
Start lesson →
Module checkpoint
Check what you have taken in
2 questions
Question 1
A well-graded gravel has D10 = 0.5 mm, D30 = 4 mm, D60 = 12 mm. What is Cc?
Question 2
What does a large uniformity coefficient Cu indicate?