Geotechnical Report

                                                                                                                                                                                                                       CLASSIFICATION OF COARSE AND FINE GRAINED SOILS
                                                                                                                                                                   Group
                                                                                      Major Divisions                                                             Symbol      Typical Names                            Field Classification of Sand and Gravel                                                         Laboratory Classification                              Laboratory Classification Criteria
                                                                                          GRAVEL (more                                                                                                                                                                                                                                                     A well graded coarse grained soil is one for which the coefficient of uniformity
                                                                                                                                                                   GW         Gravel and gravel-sand mixtures,         Wide range in grain size and substantial amounts of all intermediate sizes, not          ≤ 5% fines               Cu > 4
                                                                                                                                                                                                                                                                                                                                                           Cu > 4 and the coefficient of curvature 1 < Cc < 3. Otherwise, the soil is poorly
Coarse grainedsoil (more than 65%of soil excludingoversize fraction is




                                                                                          than half                                                                           little or no fines                       enough fines to bind coarse grains, no dry strength                                                               1 < Cc < 3
                                                                                          of coarse                                                                                                                                                                                                                                                        graded. These coefficients are given by:
                                                                                          fraction is larger                                                        GP        Gravel and gravel-sand mixtures,         Predominantly one size or range of sizes with some intermediate sizes missing,           ≤ 5% fines               Fails to comply
                                                                                                                                                                              little or no fines, uniform gravels      not enough fines to bind coarse grains, no dry strength                                                           with above                                                        (   )
                                                                                          than 2.36mm                                                                                                                                                                                                                                                                     =               and         =
                                                                                                                                                                   GM         Gravel-silt mixtures and gravel-         ‘Dirty’ materials with excess of non-plastic fines, zero to medium dry strength          ≥ 12% fines, fines       Fines behave as
                                                                                                                                                                              sand-silt mixtures                                                                                                                are silty                silt              Where D10, D30 and D60 are those grain sizes for which 10%, 30% and 60% of
                                                                                    greater than 0.075mm)




                                                                                                                                                                                                                                                                                                                                                           the soil grains, respectively, are smaller.
                                                                                                                                                                    GC        Gravel-clay mixtures and gravel-         ‘Dirty’ materials with excess of plastic fines, medium to high dry strength              ≥ 12% fines, fines       Fines behave as
                                                                                                                                                                              sand-clay mixtures                                                                                                                are clayey               clay
                                                                                                                                        SAND (more                  SW        Sand and gravel-sand mixtures,           Wide range in grain size and substantial amounts of all intermediate sizes, not          ≤ 5% fines               Cu > 6            NOTES:
                                                                                                                                        than half                             little or no fines                       enough fines to bind coarse grains, no dry strength                                                               1 < Cc < 3        1    For a coarse grained soil with a fines content between 5% and 12%,
                                                                                                                                        of coarse                                                                                                                                                                                                               the soil is given a dual classification comprising the two group symbols
                                                                                                                                        fraction                    SP        Sand and gravel-sand mixtures,           Predominantly one size or range of sizes with some intermediate sizes missing,           ≤ 5% fines               Fails to comply
                                                                                                                                                                                                                                                                                                                                                                separated by a dash; for example, for a poorly graded gravel with
                                                                                                                                        is smaller than                       little or no fines                       not enough fines to bind coarse grains, no dry strength                                                           with above             between 5% and 12% silt fines, the classification is GP-GM.
                                                                                                                                        2.36mm)                     SM        Sand-silt mixtures                       ‘Dirty’ materials with excess of non-plastic fines, zero to medium dry strength          ≥ 12% fines, fines                         2    Where the grading is determined from laboratory tests, it is defined by
                                                                                                                                                                                                                                                                                                                are silty                                       coefficients of curvature (Cc) and uniformity (Cu) derived from the
                                                                                                                                                                                                                                                                                                                                               N/A              particle size distribution curve.
                                                                                                                                                                    SC        Sand-clay mixtures                       ‘Dirty’ materials with excess of plastic fines, medium to high dry strength              ≥ 12% fines, fines                         3    Clay soils with liquid limits > 35% and ≤ 50% may be classified as being
                                                                                                                                                                                                                                                                                                                are clayey                                      of medium plasticity.
                                                                                                                                                                                                                                                                                                                                                           4    The U line on the Modified Casagrande Chart is an approximate upper
                                                                                                                                                                                                                                                                                                                                                                bound for most natural soils.
                                                                                                                                                                                                                                                                              Field Classification of                                Laboratory
                                                                                                                                                                                                                                                                                   Silt and Clay                                     Classification
                                                                                                                                                                            Group
                                                                                                                                       Major Divisions                     Symbol      Typical Names                                              Dry Strength                       Dilatancy                  Toughness            % < 0.075mm            Modified Casagrande Chart for Classifying Silts and Clays
                                                                                                                                                                                                                                                                                                                                                                         according to their Behaviour
                                                                                                                                              SILT and CLAY                 ML         Inorganic silt and very fine sand, rock flour, silty or    None to low                Slow to rapid               Low                         Below A line
                                ine grained soils (more than 35%of soil excluding




                                                                                                                                              (low to medium                           clayey fine sand or silt with low plasticity
                                                                                                                                              plasticity)
                                                                                             oversize fraction is less than 0.075mm)




                                                                                                                                                                           CL, CI      Inorganic clay of low to medium plasticity, gravelly       Medium to high             None to slow                Medium                      Above A line
                                                                                                                                                                                       clay, sandy clay

                                                                                                                                                                            OL         Organic silt                                               Low to medium              Slow                        Low                         Below A line

                                                                                                                                              SILT and CLAY                 MH         Inorganic silt                                             Low to medium              None to slow                Low to medium               Below A line
                                                                                                                                              (high plasticity)
                                                                                                                                                                            CH         Inorganic clay of high plasticity                          High to very high          None                        High                        Above A line

                                                                                                                                                                            OH         Organic clay of medium to high plasticity, organic         Medium to high             None to very slow           Low to medium               Below A line
                                                                                                                                                                                       silt

                                                                                                                                              Highly organic soil            Pt        Peat, highly organic soil                                  –                          –                           –                           –

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