soil compaction

SOILCOMPACTIONImtiaz Ur Rehman (B.Sc. Civil Engineering)

COMPACTION - Densification of soil by removing air voids using mechanical equipment

Why Soil Compaction? 1- Increase Soil

Strength 2- Reduce Soil

Settlement 3- Reduce Soil

Permeability 4- Reduce Frost

Damage 5- Reduce Erosion

Damage

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COMPACTION Vs CONSOLIDATIONCompaction – expelling air from the void space

Consolidation – extrusion of water

Solids

Water

Air

Solids

Water

Air

Compressedsoil

Load

SoilMatrix

gsoil (1) = WT1

VT1gsoil (2) =

WT1

VT2

gsoil (2) > gsoil (1)

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Factors Affecting Soil Compaction1. Moisture content2. Compaction effort

Compaction energy per unit volume (function of number of blows per layer)

For the stand proctor test: 12,400 ft-lb/ft3

For the modified proctor test: 56,000 ft-lb/ft3

3. Type of soilGrain size distributionSpecific gravity of solidsType and amount of clay materials

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What does water do for compaction?

• Lubricant• Too much water lesser density• Optimum moisture content

(=maximum dry unit weight) best compaction

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gdry max

OptimumWaterContent

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What does Compaction Effort do?

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What is role of Soil Type?

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More Useful Information

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Checking Soil Density in the Field

1- Sand Replacement Method2- Rubber Balloon Method3- Nuclear Density Gauge Method4- Core Cutter Method

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A small hole (6" x 6" deep) is dug in the compacted material to be tested. The soil is removed and weighed, then dried and weighed again to determine its moisture content. A soil's moisture is figured as a percentage. The specific volume of the hole is determined by filling it with calibrated dry sand from a jar and cone device. The dry weight of the soil removed is divided by the volume of sand needed to fill the hole. This gives us the density of the compacted soil in lbs per cubic foot. This density is compared to the maximum Proctor density obtained earlier, which gives us the relative density of the soil that was just compacted.

1- Sand Replacement Method

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Sand Replacement Method

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2- Rubber Balloon Method

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3- Nuclear Density Meter Method

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PROBLEMS IN COMPACTION EVALUATION

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PROBLEMS IN COMPACTION EVALUATION

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THANKS