Downloaded from https://www.everyspec.com MIL-STD-6192 3.1.1 Coerae-gralnedsoils. The coerse-gralnedsoils Includegravels, ~~ s~a, s=~, U sauds SOUS. The letterG is used to indicatea e gravel,and the latterS ia used to indicatea send. Gravel is materiel between3 inchesIn diameterand the Ho. k (4.7m.) sieve size, snd sand is lzate* betweenthe Ho. 4 sievesise aud the Ho. 200 (0.074sm.) sieve size. Uhare a mixtureoccurs,the primarFname is the pmdmlmmt freoticul, aud the minor fraction is used es an ~ective. For exmpl.a, a sandy graval would beamlrtvre contdning moregrwalthanssnd.
Ituillbenotadon tb grain-sizediatrlbutiondlegram,table V, that gravel is dividedInto coarseaud floe,the division being at the 3/&inch sieve size. Particles largerthau 3 Inchesin dlesbaterare termd cobbles. Sand is d.lvldadInto coarse,tiun, md fine,the divisionsbeing at the No. 10 aod ko sieve -sizes. 3.1.1.1 Coerse-grslnadsoilsvith a an.sll pa roentege of fines. When the coarae+rained soil has a small mrceateue of finessad is nomlaetic. the shapeor the gral,n-size dlstribtiion+ detemines the sec&d lett6rto be used in the eydml.
A soil is consideredpoorly gradedIf the difference in sizebetweenthe largestmd smallestgralnais small,that is, If the slope of the grain-alasdistributioncurve Is steep or if there is a de- ficiencyin any am size of particlesgiYIw a characteristic“hmp” to the STain-sizedlstributim curwm. Table V shoss grain-sizedlatributim ourvea for typicalvail gradedend poorlygraded soils. The letterP ia used to indicate a poorly graded soil; for example,GP end SP indicatepoorlygraded gravulsaud sands. Well-gradedSOIISera those which have a reasonably large Spreadbs@een the largestand the finestparticlesand have no marked deficiencyIn any one size.
The letterW la used to indicate a wall-a @ soil; for example,(W Indicatesa vsll.grededgravel,and SW Indicatesa well-gradedSaud. 3.1.1.2 Coarae-graia ad soilswith a ccmzldereblapercentageof fines. Sande and gramls that have a crsmidereblePercentamofflna s or that ex- hibit p.lsztiCi~are CIMSifled SCC- ~ the li~ti~ -t end p),SStiCit3? ind= of the fracticmpeaslngthe Ho. 40 sieveusing table III. The letter M is used* indicatefinesvith littleor no plasticityas ~ or SK The s@Ol M StSOdSfor fine+ralned SOi.bthd exhibitsfit-~ ChSTSCtel’iStiCS. The latter C is used to Indicatefines that exhibitplasticityes GC or SC. The symbolC standsfor fine-greinedSOILS that exhibitclay-likecharac- teristics.
3.1.2 Flne+rdnad matetiale. The fine-grainedsoils am not ditided accordingto grain size bUt sCC_ tO flaatiCitYend ccmpreasibility. Table III shws a plot of @aetlcity Indexv8rausI.lquldltit, end ia used in establishingthe group zgmbtifor fine-grainadsoils. 2