The satisfactory design of the foundation depends upon the accuracy with which the various soil parameters required for the design are achieved. The accuracy of soil parameters depends on the accuracy with which representative soil samples are obtained from the field.

Sampling is done so that soil and rock detailing, and laboratory testing can be done.

Laboratory tests usually include:

  • Index tests (eg, specific gravity, water content)
  • Classification tests (eg, Atterberg’s limit test on clay soils); And
  • Tests to determine engineering design parameters (for example strength, compressibility, and permeability).

Factors to be considered while taking a soil sample

  1. i) The samples should be representative of the base from which they are drawn.
  2. ii) They must be large enough to contain representative particle sizes, fabrics, and fissures and fracturing.

iii) They should be taken in such a way that they do not lose fractions of in situ soils (for example, coarse or fine particles) and where strength and compressibility tests are planned, they should be subjected to as little disturbance as possible . ,

types of soil samples
types of soil samples

non representative

Non-representative soil samples are those in which neither the in-situ soil composition, moisture content, nor soil particles are preserved.

  • they are not representative
  • They cannot be used for any test as the soil particles are either mixed or some particles may be lost.
  • Samples obtained through wash boring or percussion drilling are examples of non-representative samples.

disturbed soil samples

Disturbed soil samples are those in which soil structure and moisture content are lost, but soil particles remain intact.

  • they are representative
  • They can be used for grain size analysis, liquid and plastic limits, specific gravity, compaction tests, moisture content, organic content determination and soil classification tests performed in the laboratory.
  • For example, examples of such specimens are those obtained through cutting, grab, split spoon (SPT), etc.

undisturbed soil samples

Undisturbed soil samples are those in which the in-situ soil structure and moisture content are preserved.

  • They are representative and intact
  • they are used for consolidation, vulnerability or shear strength test (Engineering Properties)
  • more complex tasks or where clay soil Present
  • It is very difficult to get an undisturbed sample in the sand
  • Obtained using Shelby tube (thin wall), piston sampler, surface (box), vacuum, freezing, etc.

Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.