geotech report · MCU15/0087

Soil Description Explanation Sheet (2 of 2)
                                                                                                                                                                                               SOIL CLASSIFICATION INCLUDING IDENTIFICATION AND DESCRIPTION

                                                                                                                                                  FIELD IDENTIFICATION PROCEDURES
           (Excluding particles larger than 60 mm and basing fractions on estimated mass)                                                                                                                                                                                  USC                   PRIMARY NAME
                                                                                                                                                            fraction is larger than 2.36 mm




                                                                                                                                                                                                              Wide range in grain size and substantial                      GW              GRAVEL
                                                                                                                                                                                               GRAVELS
                                                                                                                                 More than half of coarse

                                                                                                                                                                                                CLEAN




                                                                                                                                                                                                              amounts of all intermediate particle sizes.
                                                                                                                                                                                                 (Little

                                                                                                                                                                                                 fines)
                                                                                                                                                                                                 or no
More than 50% of materials less than 63 mm is




                                                                                                                                                                                                              Predominantly one size or a range of sizes                     GP             GRAVEL
                                                                                                                                        GRAVELS




                                                                                                                                                                                                              with more intermediate sizes missing.
           COARSE GRAIINED SOILS




                                                                                                                                                                                               (Appreciable
                                                                                                                                                                                               WITH FINES




                                                                                                                                                                                                              Non-plastic fines (for identification                         GM              SILTY GRAVEL
                                                (A 0.075 mm particle is about the smallest particle visible to the naked eye)




                                                                                                                                                                                                GRAVELS



                                                                                                                                                                                                 of fines)
                                                                                                                                                                                                 amount




                                                                                                                                                                                                              procedures see ML below)
            larger than 0.075 mm




                                                                                                                                                                                                              Plastic fines (for identification procedures                  GC              CLAYEY GRAVEL
                                                                                                                                                                                                              see CL below)
                                                                                                                                                            fraction is smaller than 2.36 mm




                                                                                                                                                                                                              Wide range in grain sizes and substantial                     SW              SAND
                                                                                                                                 More than half of coarse


                                                                                                                                                                                               SANDS
                                                                                                                                                                                               CLEAN




                                                                                                                                                                                                              amounts of all intermediate sizes
                                                                                                                                                                                                (Little

                                                                                                                                                                                                fines)
                                                                                                                                                                                                or no




                                                                                                                                                                                                              Predominantly one size or a range of sizes                     SP             SAND
                                                                                                                                         SANDS




                                                                                                                                                                                                              with some intermediate sizes missing.
                                                                                                                                                                                               WITH FINES
                                                                                                                                                                                               (Appreciable




                                                                                                                                                                                                              Non-plastic fines (for identification                         SM              SILTY SAND
                                                                                                                                                                                                 of fines)
                                                                                                                                                                                                 SANDS


                                                                                                                                                                                                 amount




                                                                                                                                                                                                              procedures see ML below).

                                                                                                                                                                                                              Plastic fines (for identification procedures                   SC             CLAYEY SAND
                                                                                                                                                                                                              see CL below).

                                                                                                                                                                                               IDENTIFICATION PROCEDURES ON FRACTIONS <0.2 mm.
More than 50% of material less than




                                                                                                                                                                                               DRY STRENGTH          DILATANCY              TOUGHNESS
 63 mm is smaller than 0.075 mm


                                                                                                                                 SILTS & CLAYS

                                                                                                                                  less than 50




                                                                                                                                                                                               None to Low           Quick to slow          None                            ML              SILT
                                                                                                                                   Liquid limit
        FINE GRAINED SOILS




                                                                                                                                                                                               Medium to High        None                   Medium                           CL             CLAY

                                                                                                                                                                                               Low to medium         Slow to very slow      Low                              OL             ORGANIC SILT
                                                                                                                                 SILTS & CLAYS

                                                                                                                                 greater than 50




                                                                                                                                                                                               Low to medium         Slow to very slow      Low to medium                   MH              SILT
                                                                                                                                   Liquid limit




                                                                                                                                                                                               High                  None                   High                            CH              CLAY

                                                                                                                                                                                               Medium to High        None                   Low to medium                   OH              ORGANIC CLAY

   HIGHLY ORGANIC                                                                                                                                                                              Readily identified by colour, odour, spongy feel and                          Pt             PEAT
   SOILS                                                                                                                                                                                       frequently by fibrous texture.

               Low plasticity – Liquid Limit wL less than 35%.                                                                                                                                                               Medium plasticity – wL between 35% and 50%.           High plasticity – wL greater than 50%.

                                         COMMON DEFECTS IN SOIL
TERM                                                                                                                                                                                              DEFINITION                     DIAGRAM              TERM                        DEFINITION                    DIAGRAM

PARTING                                                                                                                         A surface or crack across which the                                                                                   SOFTENED A zone in clayey soil, usually adjacent
                                                                                                                                soil has little or no tensile strength.                                                                               ZONE     to a defect in which the soil has a
                                                                                                                                Parallel or sub parallel to layering                                                                                               higher moisture content than elsewhere.
                                                                                                                                (eg bedding). May be open or closed.

JOINT                                                                                                                           A surface or crack across which the soil                                                                              TUBE        Tubular cavity. May occur singly or as one
                                                                                                                                has little or no tensile strength but which is                                                                                    of a large number of separate or
                                                                                                                                not parallel or sub parallel to layering. May                                                                                     inter-connected tubes. Walls often coated
                                                                                                                                be open or closed. The term 'fissure' may                                                                                         with clay or strengthened by denser packing
                                                                                                                                be used for irregular joints <0.2 m in length.                                                                                    of grains. May contain organic matter

SHEARED Zone in clayey soil with roughly                                                                                                                                                                                                           TUBE            Roughly cylindrical elongated body of soil
ZONE    parallel near planar, curved or undulating                                                                                                                                                                                                 CAST            different from the soil mass in which it
                                                                                                                                boundaries containing closely spaced,                                                                                              occurs. In some cases the soil which
                                                                                                                                smooth or slickensided, curved intersecting                                                                                        makes up the tube cast is cemented.
                                                                                                                                joints which divide the mass into lenticular
                                                                                                                                or wedge shaped blocks.
                                                                                                                                                                                                                                                                                                                            72810-03/02/2009




SHEARED A near planar curved or undulating, smooth,                                                                                                                                                                                                   INFILLED    Sheet or wall like body of soil substance
SURFACE polished or slickensided surface in clayey                                                                                                                                                                                                    SEAM        or mass with roughly planar to irregular
                                                                                                                                soil. The polished or slickensided surface                                                                                        near parallel boundaries which cuts
                                                                                                                                indicates that movement (in many cases                                                                                            through a soil mass. Formed by infilling of
                                                                                                                                very little) has occurred along the defect.                                                                                       open joints.