soil compaction
TRANSCRIPT
SOIL SOIL COMPACTIONCOMPACTION
Soil CompactionSoil Compaction method of mechanically increasing the method of mechanically increasing the
density of soil.density of soil. in construction, this is a significant part of in construction, this is a significant part of
the building process the building process if performed improperly, settlement of the if performed improperly, settlement of the
soil could occur and result in unnecessary soil could occur and result in unnecessary maintenance costs or structural failure.maintenance costs or structural failure.
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What is Soil?What is Soil?
Soil is formed in place or deposited by Soil is formed in place or deposited by various forces of nature - such as glaciers, various forces of nature - such as glaciers, wind, lakes and rivers - residually or wind, lakes and rivers - residually or organically. organically.
important elements in soil compaction: important elements in soil compaction: Soil typeSoil type Soil moisture content Soil moisture content Compaction effort requiredCompaction effort required
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Why Compact?Why Compact? There are five principle reasons to compact There are five principle reasons to compact
soil: soil: Increases load-bearing capacity Increases load-bearing capacity Prevents frost damage Prevents frost damage Provides stability Provides stability Reduces water seepage, swelling and Reduces water seepage, swelling and
contraction contraction Reduces settling of soil Reduces settling of soil
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Types of CompactionTypes of Compaction
Vibration Vibration Impact Impact Kneading Kneading Pressure Pressure
These different types of effort are found in These different types of effort are found in the two principle types of compaction the two principle types of compaction force: force: staticstatic and and vibratoryvibratory
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Static ForceStatic Force Static Force = deadweight of the machine, Static Force = deadweight of the machine,
applying downward force on the soil applying downward force on the soil surface, compressing the soil particles. surface, compressing the soil particles.
The only way to change the effective The only way to change the effective compaction force is by adding or compaction force is by adding or subtracting the weight of the machine.subtracting the weight of the machine.
Static compaction is confined to upper Static compaction is confined to upper soil layers and is limited to any soil layers and is limited to any appreciable depth. appreciable depth.
Kneading and pressure are two examples Kneading and pressure are two examples of static compaction.of static compaction.
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Static Compactors
Vibratory ForceVibratory Force Vibratory force uses a mechanism, usually engine-Vibratory force uses a mechanism, usually engine-
driven, to create a downward force in addition to driven, to create a downward force in addition to the machine's static weight.the machine's static weight.
The vibrating mechanism is usually a rotating The vibrating mechanism is usually a rotating eccentric weight or piston/spring combination (in eccentric weight or piston/spring combination (in rammers). rammers).
The compactors deliver a rapid sequence of blows The compactors deliver a rapid sequence of blows (impacts) to the surface, thereby affecting the top (impacts) to the surface, thereby affecting the top layers as well as deeper layers. layers as well as deeper layers.
Vibration moves through the material, setting Vibration moves through the material, setting particles in motion and moving them closer particles in motion and moving them closer together for the highest density possible.together for the highest density possible.
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Vibratory Compactors
Results of Poor CompactionResults of Poor Compaction
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Soil Types and ConditionsSoil Types and Conditions Every soil type behaves differently with respect to Every soil type behaves differently with respect to
maximum density and optimum moisture. maximum density and optimum moisture. Each soil type has its own unique requirements Each soil type has its own unique requirements
and controls both in the field and for testing and controls both in the field and for testing purposes. purposes.
Soil types are commonly classified by grain size, Soil types are commonly classified by grain size, determined by passing the soil through a series determined by passing the soil through a series of sieves to screen or separate the different grain of sieves to screen or separate the different grain sizes.sizes.
A A well-gradedwell-graded soil consists of a wide range of soil consists of a wide range of particle sizes with the smaller particles filling particle sizes with the smaller particles filling voids between larger particles. voids between larger particles.
The result is a dense structureThe result is a dense structure that lends itself that lends itself well to compaction.well to compaction.
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Soil GroupsSoil Groups
There are three basic soil groups:There are three basic soil groups: Cohesive Cohesive Granular Granular Organic (not suitable for compaction)Organic (not suitable for compaction)
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Cohesive SoilsCohesive Soils Have the smallest particles Have the smallest particles Clay has a particle size range of .00004" Clay has a particle size range of .00004"
to .002". to .002". Silt ranges from .0002" to .003". Silt ranges from .0002" to .003". Clay is used in embankment fills and Clay is used in embankment fills and
retaining pond beds.retaining pond beds.
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Characteristics of Cohesive Characteristics of Cohesive SoilsSoils
dense and tightly bound together by dense and tightly bound together by molecular attraction molecular attraction
plastic when wet and can be molded, but plastic when wet and can be molded, but become very hard when dry become very hard when dry
proper water content, evenly distributed, is proper water content, evenly distributed, is critical for proper compactioncritical for proper compaction
cohesive soils usually require a force such cohesive soils usually require a force such as impact or pressureas impact or pressure
silt has a noticeably lower cohesion than silt has a noticeably lower cohesion than clay but is still heavily reliant on water clay but is still heavily reliant on water content content
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Granular soilsGranular soils range in particle size from .003" to .08" range in particle size from .003" to .08"
(sand) and .08" to 1.0" (fine to medium (sand) and .08" to 1.0" (fine to medium gravel)gravel)
known for their water-draining properties known for their water-draining properties
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Characteristics of Granular Characteristics of Granular SoilsSoils
Sand and gravel obtain maximum density in Sand and gravel obtain maximum density in either a fully dry or saturated state either a fully dry or saturated state
Testing curves are relatively flat so density Testing curves are relatively flat so density can be obtained regardless of water contentcan be obtained regardless of water content
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Moisture vs. Soil DensityMoisture vs. Soil Density Moisture content of the soil is vital to proper compaction. Moisture content of the soil is vital to proper compaction. Moisture acts as a lubricant within soil, sliding the particles Moisture acts as a lubricant within soil, sliding the particles
together. together. Too little moisture means inadequate compaction - the Too little moisture means inadequate compaction - the
particles cannot move past each other to achieve density. particles cannot move past each other to achieve density. Too much moisture leaves water-filled voids and Too much moisture leaves water-filled voids and
subsequently weakens the load-bearing ability. subsequently weakens the load-bearing ability. The highest density for most soils is at a certain water The highest density for most soils is at a certain water
content for a given compaction effort. content for a given compaction effort. The drier the soil, the more resistant it is to compaction. The drier the soil, the more resistant it is to compaction. In a water-saturated state the voids between particles are In a water-saturated state the voids between particles are
partially filled with water, creating an apparent cohesion partially filled with water, creating an apparent cohesion that binds them together. that binds them together.
This cohesion increases as the particle size decreases (as in This cohesion increases as the particle size decreases (as in clay-type soils).clay-type soils).
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Moisture vs. Soil DensityMoisture vs. Soil Density
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Soil Density TestsSoil Density Tests Soil density tests determine if proper soil Soil density tests determine if proper soil
compaction is achieved for any specific compaction is achieved for any specific construction application. construction application.
Why Test? Why Test? Measure density of soil for comparing the Measure density of soil for comparing the
degree of compaction vs. specs degree of compaction vs. specs Measure the effect of moisture on soil Measure the effect of moisture on soil
density vs. specs density vs. specs Provide a moisture density curve Provide a moisture density curve
identifying optimum moisture identifying optimum moisture
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Types of TestsTypes of Tests Tests to determine optimum moisture content Tests to determine optimum moisture content
are done in the laboratory. are done in the laboratory. The most common is the Proctor Test, or The most common is the Proctor Test, or
Modified Proctor Test. Modified Proctor Test. A particular soil needs to have an ideal (or A particular soil needs to have an ideal (or
optimum) amount of moisture to achieve optimum) amount of moisture to achieve maximum density. maximum density.
This is important not only for durability, but This is important not only for durability, but will save money because less compaction effort will save money because less compaction effort is needed to achieve the desired results. is needed to achieve the desired results.
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The Hand TestThe Hand Test Pick up a handful of soil & squeeze it in your hand. Pick up a handful of soil & squeeze it in your hand. If the soil is powdery and will not retain the shape If the soil is powdery and will not retain the shape
made by your hand, it is too dry.made by your hand, it is too dry. If it shatters when dropped, it is too dry.If it shatters when dropped, it is too dry. If the soil is moldable and breaks into only a couple If the soil is moldable and breaks into only a couple
of pieces when dropped, it has the right amount of of pieces when dropped, it has the right amount of moisture for proper compaction.moisture for proper compaction.
If the soil is plastic in your hand, leaves traces of If the soil is plastic in your hand, leaves traces of moisture on your fingers and stays in one piece when moisture on your fingers and stays in one piece when dropped, it has too much moisture for compaction.dropped, it has too much moisture for compaction.
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Proctor Test (ASTM D1557-91)Proctor Test (ASTM D1557-91) determines the maximum density of a soil needed determines the maximum density of a soil needed
for a specific job sitefor a specific job site first determines the maximum density achievable first determines the maximum density achievable
for the materials and uses this figure as a reference for the materials and uses this figure as a reference it tests the effects of moisture on soil density it tests the effects of moisture on soil density the soil reference value is expressed as a percentage the soil reference value is expressed as a percentage
of density of density these values are determined before any compaction these values are determined before any compaction
takes place to develop the compaction takes place to develop the compaction specifications. specifications.
Modified Proctor values are higher because they Modified Proctor values are higher because they take into account higher densities needed for take into account higher densities needed for certain types of construction projects. certain types of construction projects.
test methods are similar for both teststest methods are similar for both tests
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Proctor TestProctor Test Proctor TestProctor Test
A small soil sample is taken from the A small soil sample is taken from the jobsite. A standard weight is dropped jobsite. A standard weight is dropped several times on the soil. The material several times on the soil. The material weighed and then oven dried for 12 hours in weighed and then oven dried for 12 hours in order to evaluate water contentorder to evaluate water content
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Modified Proctor TestModified Proctor Test This is similar to the Proctor Test except a This is similar to the Proctor Test except a
hammer is used to compact material for hammer is used to compact material for greater impact, The test is normally greater impact, The test is normally preferred in testing materials for higher preferred in testing materials for higher shearing strength.shearing strength.
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Field TestsField Tests Sand Cone Test (ASTM D1556-90)Sand Cone Test (ASTM D1556-90)
A small hole (6" x 6" deep) is dug in the A small hole (6" x 6" deep) is dug in the compacted material to be testedcompacted material to be tested..
The soil is removed and its moisture content is The soil is removed and its moisture content is calculated.calculated.
The specific volume of the hole is determined by The specific volume of the hole is determined by filling it with calibrated dry sand from a jar and filling it with calibrated dry sand from a jar and cone device. cone device.
The dry weight of the soil removed is divided by The dry weight of the soil removed is divided by the volume of sand needed to fill the hole.the volume of sand needed to fill the hole.
This gives the density of the compacted soil in lbs This gives the density of the compacted soil in lbs per cubic foot.per cubic foot.
This density is compared to the maximum Proctor This density is compared to the maximum Proctor density obtained earlier, which gives us the density obtained earlier, which gives us the relative density of the soil that was just relative density of the soil that was just compacted.compacted.
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Nuclear Density (ASTM D2292-91)
Nuclear Density meter uses a radioactive Nuclear Density meter uses a radioactive isotope source (Cesium 137) at the soil isotope source (Cesium 137) at the soil surface (backscatter) or from a probe placed surface (backscatter) or from a probe placed into the soil (direct transmission).into the soil (direct transmission).
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Nuclear DensityNuclear Density The isotope source gives off photons The isotope source gives off photons
(usually Gamma rays) which radiate back to (usually Gamma rays) which radiate back to the matter's detectors on the bottom of the the matter's detectors on the bottom of the unit. unit.
Dense soil absorbs more radiation than Dense soil absorbs more radiation than loose soil and the readings reflect overall loose soil and the readings reflect overall density. density.
Water content (ASTM D3017) can also be Water content (ASTM D3017) can also be read, all within a few minutes. read, all within a few minutes.
A relative Proctor density with the A relative Proctor density with the compaction results from the test. compaction results from the test.
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N.Y.S.D.O.T.N.Y.S.D.O.T.
Section 203Section 203
Excavation and Excavation and EmbankmentEmbankment
New York State Department of TransportationStandard Specifications
January 2, 2002www.dot.state.ny.us
203-3.12 : C Compaction
Contractor’s responsibility:Contractor’s responsibility: Properly place and compact all materials……Properly place and compact all materials…… Correct any deficiencies resulting from Correct any deficiencies resulting from
insufficient or improper compaction…..insufficient or improper compaction….. determine the type, size and weight of determine the type, size and weight of
compactorcompactorbest suited to the work at hand, select and best suited to the work at hand, select and control the lift (layer) thickness, exert proper control the lift (layer) thickness, exert proper control overcontrol overthe moisture content of the material, and other the moisture content of the material, and other details necessary to obtain satisfactory results. details necessary to obtain satisfactory results.
New York State Department of Transportation
Standard SpecificationsJanuary 2, 2002
www.dot.state.ny.us
State’s Responsibility Department will inspect the Contractor's operations Department will inspect the Contractor's operations
and will permit the work to continue where:and will permit the work to continue where: Lift thickness is controlled and does not exceed the Lift thickness is controlled and does not exceed the
maximum allowed.maximum allowed. The compactive effort (number of passes and travel The compactive effort (number of passes and travel
speed) is uniformly applied and not less than that speed) is uniformly applied and not less than that specified for the given equipment class and lift specified for the given equipment class and lift thicknessthickness..
Engineer concludes from a visual observation that Engineer concludes from a visual observation that proper compaction has been attained.proper compaction has been attained.
Significant rutting under the action of the compactor Significant rutting under the action of the compactor is not observed on the final passes on a lift.is not observed on the final passes on a lift.
New York State Department of Transportation
Standard SpecificationsJanuary 2, 2002
www.dot.state.ny.us
State’s Responsibility (cont.) State reserves the right to perform density tests at any State reserves the right to perform density tests at any
time.time. results shall indicate that not less than 90 percent of results shall indicate that not less than 90 percent of
Standard Proctor Maximum Density is attained in any Standard Proctor Maximum Density is attained in any portion of an embankment.portion of an embankment.
95 percent in a subgrade area, or as specified for other 95 percent in a subgrade area, or as specified for other items with a percent maximum density requirement.items with a percent maximum density requirement. Contractor shall provide any assistance requested to Contractor shall provide any assistance requested to
facilitate such tests.facilitate such tests. shall include but will not be limited to excavation shall include but will not be limited to excavation
and backfill of test pits and holes.and backfill of test pits and holes. New York State Department of
TransportationStandard Specifications
January 2, 2002www.dot.state.ny.us
Compaction Equipment The selection of compaction equipment is the The selection of compaction equipment is the
Contractor'sContractor'sresponsibility. responsibility.
All compaction equipment shall be marked by a All compaction equipment shall be marked by a permanently attached manufacturer's permanently attached manufacturer's identification plate designating the name of the identification plate designating the name of the manufacturer, model number and serial number manufacturer, model number and serial number of the machine as minimum identification. of the machine as minimum identification.
Compaction equipment lacking such an original Compaction equipment lacking such an original manufacturer'smanufacturer'sidentification plate, or with altered or illegible identification plate, or with altered or illegible plates, will not be recognized as acceptable plates, will not be recognized as acceptable compaction equipmentcompaction equipment
New York State Department of Transportation
Standard SpecificationsJanuary 2, 2002
www.dot.state.ny.us
ReferencesReferencesContractors DepotContractors Depot48 Island Drive, Eastpoint, Florida, 3232848 Island Drive, Eastpoint, Florida, 32328http://www.concrete-catalog.com/http://www.concrete-catalog.com/soil_compaction.htmlsoil_compaction.html
New York State Department of TransportationNew York State Department of TransportationStandard SpecificationsStandard SpecificationsJanuary 2, 2002January 2, 2002www.dot.state.ny.uswww.dot.state.ny.us