Geotech Report - Acid Sulfate Soil Assessment - Appendix A

Notes on Description and Classification of Soil

The methods of description and classification of soils used in this report are generally based on Australian Standard AS1726-1993 “Geotechnical Site
Investigations”.

Soil description is based on an assessment of disturbed samples, as recovered from bores and excavations, or from undisturbed materials as seen in
excavations and exposures or in undisturbed samples. Descriptions given on report sheets are an interpretation of the conditions encountered at the time
of investigation,

In the case of cone or piezocone penetrometer tests, actual soil samples are not recovered and soil description is inferred based on published correlations,
past experience and comparison with bore and/or test pit data (if available).

Soil classification is based on the particle size distribution of the soil and the plasticity of the portion of the material finer than 0.425mm. The description of
particle size distribution and plasticity is based on the results of visual field estimation, laboratory testing or both. When assessed in the field, the
properties of the soil are estimated; precise description will always require laboratory testing to define soil properties.

Where soil can be clearly identified as FILL this will be noted as the main soil type followed by a description of the composition of the fill (eg. FILL — yellow-
brown, fine to coarse grained gravelly clay fill with concrete rubble). If the soil is assessed as possibly being fill this will be noted as an additional
observation,

Soils are generally described using the following sequence of terms. In certain instances, not all of the terms will be included in the soil description.
MAIN SOIL TYPE (CLASSIFICATION GROUP SYMBOL)
- strength/density, colour, structure/grain size, secondary and minor components, additional observations

Information on the definition of descriptive and classification terms follows.

SOIL TYPE and CLASSIFICATION GROUP SYMBOLS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Major Divisions Particle Size Classification Typical Names
Group Symbol
BOULDERS > 200mm
COBBLES 63 - 200mm
(GRAVELS Coarse: 20 - 63 mm Gw Well graded gravels, gravel-sand mixtures, little
COARSE (more than half of coarse} Medium: 6 - 20 mm or no fines.
GRAINED SOILS fraction is larger than) Fine: 2.36-6mm GP Poorly graded gravels and gravel-sand mixtures,
(more than half of material is|2-38 mm) little or no fines, uniform gravels.
larger than 0.075 mm) GM Silty gravels, gravel-sand-silt mixtures.
GC Clayey gravels, gravel-sand-clay mixtures,
SANDS Coarse; 0.6 - 2.36 mm sw Well graded sands, gravelly sands, little or no
(more than half of coarse] Medium: 0.2-0.6 mm fines.
fraction is smaller than} Fine: 0.075 -0.2 mm SP Poorly graded sands and gravelly sands; little or|
2.36mm) Ino fines, uniform sands.
SM Silty sands, sand-silt mixtures.
Sc Clayey sands, sand-clay mixtures.
SILTS & CLAYS ML Inorganic silts and very fine sands, silty/clayey,
(liquid limit <60 %) fine sands or clayey silts with low plasticity,
FINE CL and Cl Inorganic clays of low to medium plasticity,
GRAINED SOILS gravelly clays, sandy clays, silty clays.
(more than half of material is OL Organic silts and organic silty clays of low
smaller than 0.075 mm) Plasticity.
SILTS & CLAYS MH Inorganic silts, micaceous or diatomaceous fine’
(liquid limit >50 %) sandy or silty soils.
CH Inorganic clays of high plasticity.
OH Organic clays of medium to high plasticity,
organic silts,
HIGHLY ORGANIC Pt Peat and other highly organic soils.
SOILS

 

 

 

 

 

 

 

Notes on Description and Classification of Soil
Revision 2, November 2001 Page 1 of 2