Cohesive VS Non-Cohesive Soil

by | Sep 7, 2023

For most people, soil is little more than dirt. The messy stuff that gets on your children’s clothes and your knees when digging out the garden beds. However, it’s important to note that not all soil is the same; this is crucial when it comes to geotechnical investigations. Whilst gardeners consider soil types in terms of drainage or acidity, geotechnical companies look at whether it’s cohesive or non-cohesive soil.

When engineers analyse soil composition, they need to look at the texture, strength, as well as the consistency. This is important to note when planning for a construction project or when excavating a site. This week, Borehole Solutions, one of the UK’s leading geotechnical drilling companies, delve into the difference between soil types and why it matters.

Cohesive Soil

These are fine-grained soils, meaning the particles easily stick together. Consequently, they have an ability to be moulded and retain their shape, known as “plasticity”. Cohesive soils tend to be soft and have a high moisture content. When they are dried out, they can become as hard as cement! However, they’re also prone to shrinkage and expansion due to their natural ability to hold water. Examples of cohesive soils include; clay, silt, peat and most loam.

Non-Cohesive Soil

In comparison to cohesive soils, these are essentially the opposite. Non-cohesive soils are unable to clump together as the grains remain separate, no matter how hard you squeeze them together. They’re made up of irregular particles and environmental conditions, such as wind and rain, can easily change their consistency. Examples of non-cohesive soils include; sand, gravel and some sandy loam.

Why Does It Matter?

Different soil types require different geotechnical services and drilling techniques. For example, if you’re carrying out cable percussion drilling, then different equipment will be used dependent on the soil type. For cohesive soil, a “cutter” will be required, whereas for non-cohesive soil, a “bailer” is often used.

The soil’s ability to become compact and maintain this consistency under pressure determines whether it will provide a suitable foundation for building work. Understandably, this must be checked in advance during the planning process. Click here if you’d like to know more about the difference between cohesive and non-cohesive soil and why it’s important for engineers to know.

Our Geotechnical Services

Regardless of your soil type, we offer a wide range of geotechnical drilling solutions and have over two decades of experience between us. We’re proud to offer the following services:

  • Sonic drilling
  • Cable percussion drilling
  • Soakaway installation
  • Contamination testing
  • Window and windowless sampling
  • Restricted access drilling
  • Trial pit digging
  • Water well drilling
  • Casing and rig hire
  • Standard Penetration Testing (SPT)
  • Cone Penetration Testing (CPT)
  • Shear vane testing

Contact Us

Interested in hearing more about working on cohesive and non-cohesive soil types? Want to know more about our drilling services, then get in touch! Give us a call on 01733 200501 or click here to send us a message.