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90 CORRELATIONS OF SOIL PROPERTIES <br />TYPICAL ANGLES OF EFFECTIVE SHEARING RESISTANCE FOR COMPACTED CLAYS <br />Soil description Class deg <br />Silty clays sandsilt x SM 34 <br />Clayey sands sandla SC 31 <br />Silts and clayey silts ML 32 <br />Clays of low plasticity CL 28 <br />Clayey silts elastic silts MH 25 <br />Clays of high plasticity C 19 <br />UniGed classification system <br />plasticity index increases and she s ngttidecreases As described <br />previously the strength of clay n effec ve stress terms is basically <br />frictional so c 0 This is cert my the case th remoulded saturated <br />clays but partially saturat clays where me sous effects draw the <br />particles together to pr uce interparticle sty s may appear to <br />have a small cokes n value though this ite is a frictional <br />phenomenon <br />Typical values the angle of shearing resistance q5 fo ompacted <br />clays are give to Table 63 Values are for soils compact to the <br />maximum d density according to the standard compactio tes <br />AASHT0 9551b rammer method or BS 13771975 test 12 2 <br />yammer ethod <br />64 SHEAR STRENGTH OF GRANULAR SOILS <br />Because of their high permeability pore water pressures do not build <br />up when granular soils are subjected to shearing forces as they do <br />with clays The complication of total and effective stresses is therefore <br />avoided and the phenomenon of apparent cohesion or undrained <br />shearstrength does not occur Consequently the shear strength of <br />granular soils is defined exclusively in terms of the frictional resistance <br />between the grains as measured by the angle of shearing resistance <br />Typical values of the angle of shearing resistance for sands and <br />gravels are given in Table 64 <br />Typical values for compacted soils are given in Table 65 Values <br />refer to soil compacted to maximum dry density at optimum moisture <br />content as defined in the standard compaction test AASHTO T99 <br />55lb rammer method or BS 13771975 test 12 25kg rammer <br />method <br />A relationship between dry density or relative density and the angle <br />of shearing resistance is given by the US Navy 1982 as shown in <br />R ea ef <br />SHEAR STRENGTH 91 <br />Table 6A TYPICAL VALUES OF THE ANGLE OF SHEARING RESISTANCE OF COHESIONLESS <br />SOILS <br />degMaterial <br />Loose Dense <br />Uniform sand round grains 27 34 <br />Wellgraded sand angular grains 33 45 <br />Sandy gravels 35 So <br />Silty sand 2733 3034 <br />Inorganic silt 2730 3035 <br />Table 65 TYPICAL VALUES OF THE ANGLE OF SHEARING RESISTANCE FOR COMPACTED <br />SANDS AND GRAVELS <br />Soil description Class Angle of shearing <br />resistance 0 deg <br />Wellgraded sandgravel mixtures GW 38 <br />Poorlygraded sand gravel mixtures GP 37 <br />Silty gravels poorly graded sandgravelsilt GM 34 <br />Clayey gravels poorly graded sandgravelclay GC 31 <br />Wellgraded clean sand gravelly sands SW 38 <br />Poorlygraded clean sands gravelly sands SP 37 <br />Unified elastrieation system <br />50 <br />c <br />0 <br />y 40 <br />C O <br />m a <br />fLl OV <br />A 30 <br />0 <br />m <br />a 20 <br />Dry denalty tIn3Mqme <br />Rgure 613 Typical values of density and angle ofshearing resistance of cohesionless <br />soils modifted after US Navy 1982 <br />14 15 ia 2o 22 24