Bare Essentials of Soil Mechanics – The Effect of Gravity on Soil Strength 

In the third video in the Bare Essentials of Soil Mechanics series, Professor John Burland demonstrates how deposition under gravity of soil particles, in lakes and rivers, affects how soils behave.

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.

In this video Prof Burland uses an ingenious model to show in slow-motion how soils are laid down in rivers and lakes. He uses his model to show how soils laid down under gravity form column structures within their mass, which makes these soils stronger vertically than horizontally.

Prof Burland then goes on to illustrate how gravity effects the strength of soil at different depths. His experiment shows that the more load a foundation carries, the further it will push into the soil before it reaches equilibrium. The conclusion is that soil strength increases with depth.

Learning outcomes

This video will help learners answer questions such as:

  • How are soils formed?
  • How are soils deposited?
  • Are soils isotropic?
  • How does gravity effect soil strength?
  • How does soil strength vary with depth?
  • How does shear strength vary with depth?

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.

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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:
Graphic design:
Source: Expedition Workshed –

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