Classification – GEOCompass

CLASSIFICATION TESTS

Classification tests are used to classify soils and determine their fundamental physical characteristics. Due to their relatively low cost, these tests are frequently conducted in large numbers. This helps create a detailed understanding of the variation of soil types and properties across a site. These tests can largely be undertaken on disturbed soil samples, though intact samples may also be used in some cases.

These tests should be distributed evenly throughout the thickness of superficial deposits (soils) to allow for determination of geological stratigraphy.

NOTE: An “[Exp]” prefix signifies the guidance, which is based on professional experience of practicing geotechnical engineers and GEOCompass creators.

Water Content

'Baby' description:

“Weighs how much water is in the soil compared to how much dry dirt is there.”

Applicability:

Cohesive and cohesionless soils.

Parameter Obtained:

Water Content [%].

An indication of undrained shear strength can be obtained when undertaken in conjunction with Liquid and Plastic Limits.

Sample Quality:

Disturbed.

Class 3 or better for “Natural” water content.

Sample Size:

Fine Soil

Min 30g

Medium Soil

Min 500g

Coarse Soil

Min 3000g

Scheduling Guidance:

1 – Disturbed (tub) for general water content.

2 – Undisturbed (wax sealed) or Class 3 or better for “Natural” water content.

3 – Fine (<0.063mm); Medium (<10mm); Coarse (<31.5mm)

Scheduling Guidance:

BS 1377-2 1990
BS EN ISO 17892-1
BS5930:2015

Atterberg Liquid Limit

'Baby' description:

“Sees how much water turns soil into a liquid mush.”

Applicability:

Cohesive soils

Parameter Obtained:

Liquid Limit [%] – Water content at which soil turns into liquid state.

Sample Quality:

Disturbed or Undisturbed.

Sample Size:

200g of sieved material <0.4mm. [Exp]Approximately 1-2kg for coarser material.

Scheduling Guidance:

1 – Always specify the Cone Penetrometer method unless sample is too small.

2 – [Exp]Always specify Water Content alongside if not already scheduled separately.

3 – [Exp]Advisable to schedule Particle Size Distribution alongside.

Reference Standard:

BS 1377-2 1990
BS EN ISO 17892-12

Atterberg Plastic Limit & Plasticity Index

'Baby' description:

“Rolls wet soil into little snakes to see when it starts to crumble, and checks how squishy it is.”

Applicability:

Cohesive soils.

Parameter Obtained:

Plastic Limit [%]
Swell and shrinkage potential can be assessed when used together with the percentage offraction passing 0.425mm sieve.

Sample Quality:

Disturbed or Undisturbed.

Sample Size:

>20g from the sample prepared for the Liquid Limit test.

Scheduling Guidance:

1 – [Exp]Ensure guidance for Liquid Limit test is followed.

Reference Standard:

BS 1377-2 1990
BS EN ISO 17892-12

Particle Size Distribution (sieve)

'Baby' description:

“Shakes soil through different sized screens to see what pieces are big or small.”

Applicability:

All soils, but sieve method quantifies only fractions >0.06mm

Parameter Obtained:

Particle size distribution of sand, gravels and cobbles.

Sample Quality:

Disturbed.

Sample Size:

100g for Sand (largest fraction <2mm).
40,000g (40kg) for fractions including coarse Gravel (up tp 63mm)

Scheduling Guidance:

1 – [Exp]Always schedule wet sieve method.

Reference Standard:

BS 1377-2 1990
BS EN ISO 17892-4

Particle Size Distribution (sedimentation)

'Baby' description:

“Mixes soil in water to watch which bits sink fast or slow, to sort by size.”

Applicability:

All soils, but sedimentation method quantifies only fractions <0.06mm

Parameter Obtained:

Particle size distribution of clay and silt.

Sample Quality:

Disturbed.

Sample Size:

100g for Sand (largest fraction <2mm). 50g for Clay or Silt.

Scheduling Guidance:

1 – [Exp]Always schedule pipette method

2 – [Exp]Specify when sedimentation is required, i.e. “Undertake sedimentation where >15% fines”

Reference Standard:

BS 1377-2 1990
BS EN ISO 17892-4

Particle Density

'Baby' description:

“Checks how heavy the solid bits of the soil are, not counting spaces or water.”

Applicability:

All soils <4mm

Parameter Obtained:

Particle Density [Mg/m3] useful for analysis of data from compaction and consolidation tests.

Sample Quality:

Disturbed.

Sample Size:

Minimum 10g
[Exp] Aim at 1000-1500g ‘raw’ soil material.

Scheduling Guidance:

1 – Specify on samples used in compaction tests.

Reference Standard:

BS 1377-2 1990
BS EN ISO 17892-3
BS5930:2015

Bulk & Dry Density

'Baby' description:

“Measures how much the whole soil (with air and water) weighs in a given space, both wet and dry.”

Applicability:

All soils

Parameter Obtained:

Bulk Density [Mg/m3].

Dry Density [Mg/m3].

Dry density can be used to determine voids ratio, porosity and saturation.

Sample Quality:

Disturbed.

Sample Size:

Minimum 50cm3
Linear measurement method: any size suitable for further testing.
Immersion in water & Water displacement methods: Lump of min 100mm in each direction

Scheduling Guidance:

None

Reference Standard:

BS 1377-2 1990

BS EN ISO 17892-2

BS5930:2015

Shrinkage

'Baby' description:

“Sees how much a lump of wet soil shrinks when it dries out.”

Applicability:

All soils <0.4mm

Parameter Obtained:

Shrinkage limit [%].

Sample Quality:

Disturbed for Subsidary & Linear methods.
Undisturbed for Definitive method.

Sample Size:

A cylinder for Definitive method.
50g sample for Subsidary method.
150g for Linear method.

Scheduling Guidance:

None

Reference Standard:

BS 1377-2 1990