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Soil Density - Standard vs Modified Proctor

2003 Keystone Retaining Wall Systems912/30/03 Soil Density - Standard vs Modified ProctorReinforced soil structures routinely specify that all soils be compacted to 95% of the maximumdensity determined by ASTM D698 - Standard Proctor Densityfor conformance with thedesign. However, Standard Proctordensity criteria is typically utilized in the Eastern US where-asModified Proctordensity criteria is typically utilized in the Western US which can createsome conflicting specification has been done showing the relationship betweenStandardandModified Proctordensi-ty testing for different soils types as indicated below:140130120110100908070 , water content in %05101520253035A1B1C1A2B2C2A3B3C3A- Modified ProctorB- Standard ProctorC- 15 blow ProctorSoil 2(Sand)Soil 1(Silty Sand)So il 3(Clay) moisture - Density Relationships(Ref. Tschebotarioff - 1973)TypeSand SiltClayLLPISoil 1 - Silty Sand80% 15%5%171 Soil 2 - Sand92%5%3%NPNPSoil 3 - Clay10% 28% 62%6847 Characteristics of Three SoilsMax Dry Density ,pcfOptimum moisture ,%TypeABCABCSoil 1 - Silty Sand13212512381010 Soil 2 - Sand113110108indindindSoil 3 - Clay1028883202831 Summary of DataTypeStandard 95% Standard % of ModifiedSoil 1 - Silty Sand12511990%Soil 2 - Sand11010593%Soil 3 - Clay888482%95% Standard vs Modified Proctor ComparisonIt is obvious from this limited data that a simple conclusion can not be drawn but some generalguidelines can be establi

Standard Proctor density except for fine grained soils (ie: clay) where the difference may be significantly larger. ∗ Modified Proctor testing typically requires a lower optimum moisture content for achieving maximum density which is desirable for Keystone retaining wall construction and performance especially with silts and silty soils.

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  Maximum, Density, Optimum, Moisture, Maximum density, Optimum moisture

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Transcription of Soil Density - Standard vs Modified Proctor

1 2003 Keystone Retaining Wall Systems912/30/03 Soil Density - Standard vs Modified ProctorReinforced soil structures routinely specify that all soils be compacted to 95% of the maximumdensity determined by ASTM D698 - Standard Proctor Densityfor conformance with thedesign. However, Standard Proctordensity criteria is typically utilized in the Eastern US where-asModified Proctordensity criteria is typically utilized in the Western US which can createsome conflicting specification has been done showing the relationship betweenStandardandModified Proctordensi-ty testing for different soils types as indicated below:140130120110100908070 , water content in %05101520253035A1B1C1A2B2C2A3B3C3A- Modified ProctorB- Standard ProctorC- 15 blow ProctorSoil 2(Sand)Soil 1(Silty Sand)So il 3(Clay) moisture - Density Relationships(Ref. Tschebotarioff - 1973)TypeSand SiltClayLLPISoil 1 - Silty Sand80% 15%5%171 Soil 2 - Sand92%5%3%NPNPSoil 3 - Clay10% 28% 62%6847 Characteristics of Three SoilsMax Dry Density ,pcfOptimum moisture ,%TypeABCABCSoil 1 - Silty Sand13212512381010 Soil 2 - Sand113110108indindindSoil 3 - Clay1028883202831 Summary of DataTypeStandard 95% Standard % of ModifiedSoil 1 - Silty Sand12511990%Soil 2 - Sand11010593%Soil 3 - Clay888482%95% Standard vs Modified Proctor ComparisonIt is obvious from this limited data that a simple conclusion can not be drawn but some generalguidelines can be established when usingModified Proctordensity testing in lieu ofStandardProctortesting for quality assurance testing of reinforced soil structures: 90% - 92% ofModified Proctordensity is roughly equivalent to the specified 95% Standard Proctordensity except for fine grained soils (ie: clay) where the difference maybe significantly larger.

2 Modified Proctortesting typically requires a lower optimum moisture content forachieving maximum Density which is desirable for Keystone retaining wall constructionand performance especially with silts and silty soils. The Density difference betweenModified ProctorandStandard Proctordensity testingappears to increase with the percentage of fines in the soil matrix while the optimummoisture content decreases . It may be prudent to utilize 90% of Modified Proctordensity and optimum moisture content when working with fine grained soils such asclays for best results.


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