Soil density stand vs modified proctor relationship

Soil density stand vs modified proctor relationship

1. ©2003KeystoneRetainingWallSystems912/30/03
SoilDensity-StandardvsModifiedProctor
Reinforcedsoilstructuresroutinelyspecifythatallsoilsbecompactedto95%ofthemaximum
densitydeterminedbyASTMD698-StandardProctorDensityforconformancewiththe
design.However,StandardProctordensitycriteriaistypicallyutilizedintheEasternUSwhere-
asModifiedProctordensitycriteriaistypicallyutilizedintheWesternUSwhichcancreate
someconflictingspecificationproblems.
ResearchhasbeendoneshowingtherelationshipbetweenStandardandModifiedProctordensi-
tytestingfordifferentsoilstypesasindicatedbelow:
140
130
120
110
100
90
80
70
ω,watercontentin%
0 5 10 15 20 25 30 35
A1
B1
C1
A2
B2
C2
A3
B3
C3
A-ModifiedProctor
B-StandardProctor
C-15blowProctor
Soil2
(Sand)
Soil1
(SiltySand)
Soil3
(Clay)
Moisture-DensityRelationships
(Ref.Tschebotarioff-1973)
Type Sand Silt Clay LL PI
Soil1-SiltySand 80% 15% 5% 17 1
Soil2-Sand 92% 5% 3% NP NP
Soil3-Clay 10% 28% 62% 68 47
CharacteristicsofThreeSoils
MaxDryDensity,pcf OptimumMoisture,%
Type A B C A B C
Soil1-SiltySand 132 125 123 8 10 10
Soil2-Sand 113 110 108 ind ind ind
Soil3-Clay 102 88 83 20 28 31
SummaryofData
Type Standard 95%Standard%ofModified
Soil1-SiltySand 125 119 90%
Soil2-Sand 110 105 93%
Soil3-Clay 88 84 82%
95%StandardvsModifiedProctorComparison
Itisobviousfromthislimiteddatathatasimpleconclusioncannotbedrawnbutsomegeneral
guidelinescanbeestablishedwhenusingModifiedProctordensitytestinginlieuofStandard
Proctortestingforqualityassurancetestingofreinforcedsoilstructures:
∗90%-92%ofModifiedProctordensityisroughlyequivalenttothespecified95%
StandardProctordensityexceptforfinegrainedsoils(ie:clay)wherethedifferencemay
besignificantlylarger.
∗ModifiedProctortestingtypicallyrequiresaloweroptimummoisturecontentfor
achievingmaximumdensitywhichisdesirableforKeystoneretainingwallconstruction
andperformanceespeciallywithsiltsandsiltysoils.
∗ThedensitydifferencebetweenModifiedProctorandStandardProctordensitytesting
appearstoincreasewiththepercentageoffinesinthesoilmatrixwhiletheoptimum
moisturecontentdecreases.Itmaybeprudenttoutilize90%ofModifiedProctor
densityandoptimummoisturecontentwhenworkingwithfinegrainedsoilssuchas
claysforbestresults.