Response to Information Request - MCU12/0184

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Soil Description Explanation Sheet (1 of 2)


DEFINITION:                                                                     DENSITY OF GRANULAR SOILS
In engineering terms soil includes every type of uncemented
                                                                                           TERM                            DENSITY INDEX (%)
or partially cemented inorganic or organic material found in

the ground. In practice, if the material can be remoulded or                                                                Less than 15
                                                                                         Very loose
disintegrated by hand in its field condition or in water it is
described as a soil. Other materials are described using rock                              Loose                               15   -
                                                                                                                                        35
description terms.
                                                                                       Medium Dense                            35   -
                                                                                                                                        65
CLASSIFICATION SYMBOL & SOIL NAME
                                                                                           Dense                               65   -
                                                                                                                                        85
Soils are described in accordance with the Unified Soil
Classification    (UCS) as shown in the table on Sheet 2.                               Very Dense                         Greater than 85



PARTICLE SIZE DESCRIPTIVE TERMS

      NAME         SUBDIVISION                              SIZE
                                                                                MINOR COMPONENTS
      Boulders                                           >200 mm
                                                                                TERM                 ASSESSMENT                 PROPORTION OF
                                                                                                         GUIDE               MINOR COMPONENT IN:
      Cobbles                                       63 mm to 200 mm

                                                                                Trace of        Presence just detectable      Coarse grained soils:
       Gravel               coarse                   20mmto 63 mm
                                                                                                by feel or eye, but soil      <5%
                           medium                     6 mm to 20 mm
                                                                                                properties little or no
                                                                                                different to general          Fine grained soils:
                                                                                                properties of primary         <15%
                                fine                 2.36 mm to 6 mm
                                                                                                component.
       Sand                 coarse                 600 flm to 2.36 mm
                                                                                With some Presence easily detected            Coarse grained soils:
                                                                                          by feel or eye, soil                5 -12%
                           medium                   200 J.lm to 600 I’m
                                                                                          properties little different         Fine grained soils:
                                                     75 flm to 200 I’m                          to general properties of      15 30%
                                                                                                                                 -


                                fine
                                                                                                primary component.



                                                                                SOIL STRUCTURE
MOISTURE CONDITION
Dry       Looks and feels dry. Cohesive and cemented soils                                 ZONING                            CEMENTING
          are hard, friable or powdery. Uncemented granular
          soils run freely through hands.                                       Layers     Continuous across   Weakly           Easily broken up by
                                                                                           exposure or sample. cemented         hand in air or water.
Moist     Soil feels cool and darkened in colour. Cohesive
          soils can be moulded. Granular soils tend to cohere.                  Lenses     Discontinuous           Moderately Effort is required to
                                                                                           layers of lenticular    cemented   break up the soil by
Wet       As for moist but with free water forming on hands                                shape.                               hand in air or water.
          when handled.
                                                                                Pockets Irregular inclusions
                                                                                        of different material.



CONSISTENCY OF COHESIVE SOILS

                UNDRAINED                                                       GEOLOGICAL ORIGIN
 TERM           STRENGTH                              FIELD GUIDE
                                                                                WEATHERED IN PLACE SOILS
                 Su (kPa)
                                                                                Extremely            Structure and fabric of parent rock visible.
  Very Soft        <12                 A finger can be pushed well into the     weathered
                                       soil with little effort.                 material

 Soft             12   -
                           25          A finger can be pushed into the soil
                                                                                Residual soil        Structure and fabric of parent rock not visible.
                                       to about 25mm depth.


  Firm            25   -
                           50          The soil can be indented about 5mm
                                                                                TRANSPORTED SOILS
                                       with the thumb, but not penetrated.
                                                                                Aeolian soil         Deposited by wind.
  Stiff          50 -100               The surface of the soil can be
                                       indented with the thumb, but not         Alluvial soil        Deposited by streams and rivers.
                                       penetrated.
                                                                                Colluvial soil       Deposited on slopes (transported downslope
 Very Stiff      100   -
                           200         The surface of the soil can be marked,                        by gravity).
                                       but not indented with thumb pressure.
                                                                                Fill                 Man made deposit. Fill may be significantly
  Hard            >200                 The surface of the soil can be marked                         more variable between tested locations than

                                       only with the thumbnail.                                      naturally occurring soils.

  Friable           -                  Crumbles or powders when scraped         Lacustrine soil      Deposited by lakes.
                                       by thumbnail.
                                                                                Marine soil          Deposited in ocean basins, bays, beaches
                                                                                                     and estuaries.