20517 App N.pdf [As Published] · 132007.1259

Notes on Description and Classification of Soil

DESCRIPTIVE TERMS FOR MATERIAL PROPORTIONS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Coarse Grained Soils Fine Grained Soils
% Fines Modifier % Coarse Modifier
<5 Omit, or use ‘trace’ <15 Omit, or use trace.
5-12 — |Describe as ‘with clay/silt’ as applicable. 15-30 |Describe as ‘with sand/gravel’ as applicable.
>12 Prefix soil as ‘silty/clayey’ as applicable > 30 Prefix soil as ‘sandy/gravelly’ as applicable.
STRENGTH TERMS ~ COHESIVE SOILS
Strength Undrained Shear Field Guide to Strength
Term Strength
Very soft <12 kPa Exudes between the fingers when squeezed in hand.
Soft 12-25 kPa Can be moulded by light finger pressure.
Firm 25 - 50 kPa Can be moulded by strong finger pressure.
Stiff 50-100 kPa Cannot be moulded by fingers, can be indented by thumb.
Very stiff 100 - 200 kPa Can be indented by thumb nail.
Hard > 200 kPa Can be indented with difficulty by thumb nail.
DENSITY TERMS ~ NON COHESIVE SOILS
Density Density SPT “N” CPT Cone
Term Index Resistance
Very loose <15% 0-5 0-2MPa
Loose 15-35 % 5-10 2-5 MPa
Medium dense 35 - 65 % 10-30 5-15 MPa
Dense 65-85% 30-50 15-25 MPa
Very dense > 85% > 50 > 25 MPa
COLOUR

 

The colour of a soil will generally be described in a ‘moist’ condition using simple colour terms (eg. black, grey, red, brown etc.) modified as necessary by

 

 

 

 

 

 

 

 

 

 

 

 

“pale”, “dark”, “light” or “mottled”. Borderline colours will be described as a combination of colours (eg. grey-brown).

EXAMPLE

eg: CLAYEY SAND (SC) - medium dense, grey-brown, fine to medium grained with silt.

Indicates a medium dense, grey-brown, fine to medium grained clayey sand with silt.

 

Notes on Description and Classification of Soil
Revision 2, November 2001