Geotechnical Drilling Hammond What is the Difference Between Disturbed and Undisturbed Soil Samples in Geotechnical Drilling?

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Hammond, Louisiana geotechnical drilling companies can provide engineers and site planners with vital information about a site by extracting many different types of samples, including soil samples, rock samples and even ice cores in arctic drilling projects. Two of the most common types of soil samples are disturbed soil samples and undisturbed soil samples.

So what are disturbed and undisturbed soil samples, how are they different and what information can they provide engineers, developers, builders and site planners? Well, that’s precisely what we’ll explore today!

What are Disturbed and Undisturbed Soil Samples in Geotechnical Drilling?

Hammond engineers and developers may seek out disturbed and undisturbed soil samples from a site, as they are critical for determining the site’s engineering properties, while also verifying geophysical properties.

A disturbed soil sample is one that has been disturbed or “rearranged” to some degree through the drilling or excavation process. The sample’s disturbance can result in the loss of some data, such as the degree of compaction, overall ground stability and the moisture content of a certain layer of soil (particularly in cases where multiple layers are intermingled during the drilling, extraction or excavation process.)

But disturbed soil samples tend to be much easier (and faster) to extract and they can provide a lot of important basic information concerning the soil composition, including:

  • Soil type
  • Gradation
  • Consistency
  • Classification
  • Stratification
  • Contamination
  • Moisture density relations
  • CBR

Undisturbed soil sample extraction is more challenging and time-consuming, as you’re essentially tasked with removing an undisturbed chunk of earth exactly as-is.

Undisturbed soil samples provide vital data into the degree of compaction and ground density, the moisture content at various levels and in various layers of the earth. Assuming the sample is extracted without any disruption, then this type of sample is more representative of the actual underground conditions at the site of the geotechnical drilling.

Hammond engineers can derive a wealth of data from undisturbed samples, including:

  • Strength and integrity
  • Permeability
  • Compressibility and settlement
  • Unit weight
  • Natural moisture content
  • Fractures and discontinuities
  • Fissures of sub-surface formations

Special care must be taken when transporting undisturbed samples because otherwise, the properties of the sample could be altered. If the sample is not properly packed for transport or if the transportation process involves lots of jarring, sudden movements, this could alter the sample, rendering it useless for determining specific properties or values.

*Disclaimer: The views expressed here are those of the authors and do not necessarily represent or reflect the views of Amdrill Inc*