Bare Essentials of Soil Mechanics – The Effect of Particle Size and Shape on Soil Strength 

In the fourth video in the Bare Essentials of Soil Mechanics series, Professor John Burland demonstrates how soil grading (the range of particle sizes in a soil) and soil shape affect a soil’s ability to resist load.

In this video Professor Burland uses his base friction model, introduced in video 3 to model how changes to a soil affect its ability to resist the weight of a foundation pressing down on it. He compares the strength of a well-graded soil with a uniformly graded soil and demonstrates that a well-graded soil has greater ability to resist load.

Using the same model Professor Burland demonstrates the effect of particle shape on soil strength by comparing the behaviour of a soil made of round particles with the behaviour of a soil made of circular particles. The conclusion is the more angular the soil particles, the stronger the soil.

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Learning outcomes

This video will help learners answer questions such as:

  • What is a uniformly graded soil?
  • What is a well-graded soil?
  • How does soil grading affect soil strength?
  • How does particle size affect soil strength?
  • How does particle shape affect soil strength?

About the Bare Essentials of Soil Mechanics Series

This video is part of the Bare Essentials of Soil Mechanics series, funded by the Ove Arup Foundation, in which Professor John Burland draws on his many years of practice in geotechnical engineering and teaching to provide listeners with what he regards to be the key knowledge that geotechnical engineers need to understand about soil mechanics in engineering practice. 

Prof Burland is based at Imperial College London and has worked on hundreds of interesting projects, the most famous of which was stabilising the Leaning Tower of Pisa. 

This work is licensed under the Creative Commons Attribution-NonCommercial 3.0 Unported License. To view a copy of this license click here.


  • Written and presented by: Prof John Burland, Imperial College, London
  • Concept design: Think Up
  • Graphic design: thomas.matthews
  • Direction/Production: Aeries Films
  • Source: Expedition Workshed –
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