Compiled Reference Documents - OPW25/0053 (As Published)

                                                                                                 Terminology
Soil Descriptions                                                                                   Symbols
                                                                                                Abbreviations

Soil Condition
Moisture
The moisture condition of soils is assessed relative to the plastic limit for fine grained soils, while for coarse
grained soils it is assessed based on the appearance and feel of the material. The moisture condition of a
material is considered to be independent of stratigraphy (although commonly these are related), and this
data is presented in its own column on logs.
 Applicability            Term                        Tactile Assessment                        Abbreviation
                                                                                                     code
 Fine              Dry of plastic limit Hard and friable or powdery                           `w<PL`
                   Near plastic limit   Can be moulded                                        `w=PL`
                   Wet of plastic limit Water residue remains on hands when `w>PL`
                                        handling
                   Near liquid limit    “oozes” when agitated                                 `w=LL`
                   Wet of liquid limit  “oozes”                                               `w>LL`
 Coarse            Dry                  Non-cohesive and free running                         `D`
                   Moist                Feels cool, darkened in colour, particles may `M`
                                        stick together
                   Wet                  Feels cool, darkened in colour, particles may `W`
                                        stick together, free water forms when handling
The abbreviation code `NDF`, meaning “not-assessable due to drilling fluid use” may also be used.
Note, observations relating to free ground water or drilling fluids are provided independent of soil moisture
condition.
Consistency/Density/Compaction/Cementation/Extremely Weathered Material
These concepts give an indication of how the material may respond to applied forces (when considered in
conjunction with other attributes of the soil). This behaviour can vary independent of the composition of
the material, and on logs these are described in an independent column and are generally mutually
exclusive (i.e it is inappropriate to describe both consistency and compaction at the same time). The
method by which the behaviour is described depends on the behaviour model and other characteristics of
the soil as follows:
 •   In fine grained soils, the “consistency” describes the ease with which the soil can be remoulded, and is
     generally correlated against the materials undrained shear strength;
 •   In granular materials, the relative density describes how tightly packed the particles are, and is
     generally correlated against the density index;
 •   In anthropogenically modified materials, the compaction of the material is described qualitatively;
 •   In cemented soils (both natural and anthropogenic), the cemented “strength” is described
     qualitatively, relative to the difficulty with which the material is disaggregated; and
 •   In soils of extremely weathered material origin, the engineering behaviour may be governed by relic
     rock features, and expected behaviour needs to be assessed based the overall material description.
Quantitative engineering performance of these materials may be determined by laboratory testing or
estimated by correlated field tests (for example penetration or shear vane testing). In some cases,
performance may be assessed by tactile or other subjective methods, in which case investigation logs will
show the estimated value enclosed in round brackets, for example `(VS)`.
Consistency (fine grained soils)
 Consistency                     Tactile Assessment                           Undrained         Abbreviation
    Term                                                                          Shear            Code
                                                                            Strength (kPa)
 Very soft       Extrudes between fingers when squeezed                     <12                 `VS`
 Soft            Mouldable with light finger pressure                       >12 - ≤25           `S`
 Firm            Mouldable with strong finger pressure                      >25 - ≤50           `F`
 Stiff           Cannot be moulded by fingers                               >50 - ≤100          `St`
 Very stiff      Indented by thumbnail                                      >100 - ≤200         `VSt`
 Hard            Indented by thumbnail with difficulty                      >200                `H`
 Friable         Easily crumbled or broken into small pieces by hand        -                   `Fr`
Relative Density (coarse grained soils)
      Relative Density Term                     Density Index                       Abbreviation Code
 Very loose                           <15                                    `VL`
 Loose                                >15 - ≤35                              `L`
 Medium dense                         >35 - ≤65                              `MD`
 Dense                                >65 - ≤85                              `D`
 Very dense                           >85                                    `VD`
Note, tactile assessment of relative density is difficult, and generally requires penetration testing, hence a
tactile assessment guide is not provided.


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