Geotech 95141.00.R.001

Description and Classification Methods
The methods of description and classification of      The proportions of secondary constituents of soils
soils and rocks used in this report are generally     are described as follows:
based on Australian Standard AS1726:2017,             In fine grained soils (>35% fines)
Geotechnical Site Investigations. In general, the
                                                        Term               Proportion       Example
descriptions include strength or density, colour,
                                                                           of sand or
structure, soil or rock type and inclusions.
                                                                             gravel
                                                        And                  Specify     Clay (60%) and
Soil Types
                                                                                          Sand (40%)
Soil types are described according to the
predominant particle size, qualified by the grading     Adjective             >30%         Sandy Clay
of other particles present:                            With               15 – 30%       Clay with sand
                                                       Trace               0 - 15%       Clay with trace
    Type                   Particle size (mm)                                                 sand
    Boulder                       >200
    Cobble                      63 - 200              In coarse grained soils (>65% coarse)
                                                      - with clays or silts
    Gravel                      2.36 - 63
                                                        Term                Proportion     Example
    Sand                      0.075 - 2.36
                                                                             of fines
    Silt                     0.002 - 0.075
                                                        And                  Specify   Sand (70%) and
    Clay                         <0.002                                                  Clay (30%)
                                                        Adjective             >12%       Clayey Sand
The sand and gravel sizes can be further
                                                        With                 5 - 12%    Sand with clay
subdivided as follows:
                                                       Trace                0 - 5%      Sand with trace
    Type                   Particle size (mm)                                                clay
    Coarse gravel                19 - 63
                                                      In coarse grained soils (>65% coarse)
    Medium gravel               6.7 - 19              - with coarser fraction
    Fine gravel                2.36 – 6.7               Term               Proportion     Example
    Coarse sand                0.6 - 2.36                                   of coarser
    Medium sand                0.21 - 0.6                                    fraction
    Fine sand                 0.075 - 0.21              And                  Specify   Sand (60%) and
                                                                                        Gravel (40%)
                                                        Adjective             >30%      Gravelly Sand
Definitions of grading terms used are:                 With               15 - 30%      Sand with gravel
     Well graded - a good representation of all       Trace              0 - 15%       Sand with trace
      particle sizes                                                                        gravel
     Poorly graded - an excess or deficiency of
      particular sizes within the specified range     The presence of cobbles and boulders shall be
     Uniformly graded - an excess of a particular    specifically noted by beginning the description with
      particle size                                   ‘Mix of Soil and Cobbles/Boulders’ with the word
     Gap graded - a deficiency of a particular       order indicating the dominant first and the
      particle size with the range                    proportion of cobbles and boulders described
                                                      together.




                                                                                                 May 2019