soil compaction.pdf

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    Contents

    Introduction.

    Proctor test.

    Dry density in field.

    Field compaction.

    Relative compaction.

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    Introduction

    Historical background.

    Definition.Effect of compaction on soil.

    Types of compaction.

    The factors affecting on compaction.

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    Historical Background

    Soil compaction is known since ancient

    times, when man began to build dams where

    the compaction was done by passing the

    large numbers of workers and animals on the

    soil several times.

    Proctorpresented his

    research in 1933,

    enter the scientific method

    in this field.

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    Definition

    Compaction is the application of mechanical

    energy to a soil to rearrange the particles and

    reduce the void ratio.

    Loose soil Compacted soil

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    Effect of compaction on soil

    Improve shear strength.

    Reduce compressibility. Decrease permeability.

    Reduce shrink/swell potential.

    Reduce liquefaction potential. Reduce compression due to wetting.

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    Types of compaction

    There are four types of compaction effort on

    soil or asphalt:

    Vibration

    Impact

    Kneading

    Pressure

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    These different types of effort are found in

    the two principle types of compaction force,staticand vibratory.

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    Static force is simply the deadweight of the

    machine, applying downward force on the

    soil surface, compressing the soil particles. Kneading and pressure are two examples of

    static compaction.

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    Vibratory force uses a mechanism, usually

    engine-driven, to create a downward force in

    addition to the machinesstatic weight.

    The vibrating mechanism is usually a rotating

    eccentric weight or piston/spring

    combination (in rammers).

    The compactors deliver a rapid sequence of

    blows (impacts) to the surface, thereby

    affecting the top layers as well as deeper

    layers.

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    Factors affecting Compaction

    Water content of the soil.

    The type of soil being compacted.

    The amount of compactive energy used.

    The type of compaction.

    The admixtures.

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    Proctor testPurpose.

    Test Types.

    Compaction Effort.Apparatus.

    Test procedure.

    Results.

    Zero air voids lines.

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    Purpose

    This laboratory test is performed to

    determine the relationship between the

    moisture content and the dry density of a soilfor a specified compactive effort.

    The compactive effort is the amount of

    mechanical energy that is applied to the soilmass.

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    Test Types

    Two types of compaction tests are routinelyperformed:

    i. The Standard Proctor Test.

    ii. The Modified Proctor Test.

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    What is the differencebetween the two types

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    S. Proctor Test M. Proctor TestHammer weight 2.5 KgHammer weight 4.5 KgFall distance 30.5 cm Fall distance 45 cm

    Three equal layers Five equal layers25 drops 25 drops

    6.058 kg.cm/cm 26.814 kg.cm/cm

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    Compaction Effort

    Compaction Effort is calculated with the

    following parameters:

    For Standard Proctor test:

    For Modified Proctor test:

    Where Eis Compaction Energy.

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    Apparatus

    Mold Manual hammer

    Extruder Digital Scale

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    Sieve #4 Straight edge

    Graduated cylinder Drying oven

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    Mixing pan Trowel

    Moisture cans

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    Test Procedure

    1) Drying sample of the soil after it is crushed(about 3 kg of passers-by sieve #4).

    2) Adding amount of water according to the kind

    of soil.3) The sample is placed in the mold in three layers

    consisting of a cylinder circle.

    4) Each layer of the three layers is compacted bydropping 25 bowls with a hammer weighs 2.5

    kg and fall from the height of 30.5 cm.

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    5) Carefully remove the collar and trim off the

    compacted soil so that it is completely evenwith the top of the mold using the trowel.

    6) Weigh the mold cylinder including contents

    of the soil to calculate the density of the wetsample and the water content her.

    7) Remove the soil from the mold using amechanical extruder and take soil moisture

    content samples from the top and bottom ofthe sample. Fill the moisture cans with soiland determine the water content.

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    8) Repeat the test 6 times with increasing the

    water content by (about 2%).

    9) Draw the relationship between the dry

    density and the water content.

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    Soil sifting Adding amount of water

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    The sample is placed

    in the moldCompaction of

    the sample

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    Taking samplesWeigh the mold

    including the sample

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    Results

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    Zero Air Voids Curve

    The zero air voids (ZAV) line is the combination

    of moisture and density that produce complete

    saturation of the soil or the obtained when

    there is no air in the void spaces. The compaction curve theoretically does not

    cross this line but becomes parallel to it.

    Remember that the values of water content, wetunit weight, and specific gravity are not constant

    throughout the soil.

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    There could also be variability in the test

    results. Variability can result in points on the

    compaction curve above the ZAV line(S>100%).

    These data points should not be thrown out.

    Basic weight volume relationships are usedto develop and equation for the ZAV line.

    Recall that: (.W= .e where = 1)

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    Note that and are constants for a given

    soil.

    Therefore the ZAV line is a linear function ofwater content. To draw the ZAV line, simply

    enter values of and compute the

    corresponding value of

    .

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    Dry density in field

    Core cutter method.

    Sand replacement method.

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    CORE CUTTER METHOD

    Core cutters are used for testing thecompaction of cohesive/clay soils placed asfill.

    The cylindrical cores of standard volume,13cms long and 10cms diameter.

    They have a sharpened edge at one end toimprove penetration of the soil surface.

    These cores are driven fully into the surfaceto be tested, they are removed from theground without disturbing the core contents.

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    Apparatus

    Cylindrical corecutter.

    Steel rammer.

    Steel dolly. Balance.

    Spade or pickaxe or

    crowbar.

    Trimming Knife.

    Oven.

    Water contentcontainers.

    Desiccator.

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    Test Procedure

    1) Measure the height and internal diameter of

    the core cutter.

    2) Weight the clean core cutter.

    3) Clean and level the ground where the

    density is to be determined.

    4) Press the cylindrical cutter into the soil to its

    full depth with the help of steel rammer.

    5) Remove the soil around the cutter by spade.

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    6) Lift up the cutter.7) Trim the top and bottom surfaces of the

    sample carefully.

    8) Clean the outside surface of the cutter.9) Weight the core cutter with the soil.

    10) Remove the soil core from the cutter andtake the representative sample in the watercontent containers to determine themoisture content

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    Sand Replacement Method

    This method, often called the sand-conemethod, may be used for both fine-grained

    and coarse-grained materials.

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    Sand cone apparatus which consists of a one-

    gallon plastic bottle with a metal cone

    attached to it.

    One-Gallon plastic can with cap.

    Sensitive scale.

    Base plate.

    Tools for excavating a hole in the ground.

    Apparatus

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    Clean, uniformly graded sand ranging from#20 to #30 sieve.

    Proctor compaction mold without attached

    extension. Plastic air-tight bag.

    Metal tray with a hole in the center.

    Oven.

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    Test procedure:

    1) Weigh of Proctor mold + Base ().

    2) Determination of "dry density " of soil.

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    Pour the sand into the compaction mold.

    Level the surface (Do not disturb the mold as

    the sand may rearrange and get compacted).

    Compaction mold filled with sand.

    Weigh of proctor mold+base+ Sand ().

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    From , we can get ().

    Volume of mold is known (v). Dry unit weight, (sand) = (-) /

    3) Weigh of plastic Gallon + Cone + Sand,

    (before use).

    4) Determination of the weight of sand the

    cone can contains ().

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    Close the valve attached to the cone.

    Turn the cone and gallon upside down on the

    tray.

    Open the valve, sand flows from the gallon to

    the cone, after the flow stops close the valve

    and take the gallon + cone from the tray.

    Weigh of plastic Gallon + Cone + Sand,

    (after use).

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    Weight of the sand to fill the cone,

    =

    -

    .

    5) Weight of plastic Gallon + Cone + Sand,

    (before use).

    6. Go to the field where the soil's unit weightis to be measured, place the metal tray and

    fasten the 4 screws.

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    7) Dig up a 10 to 15 cm deep hole.

    8) Put the retrieved soil into the plastic. All of

    the soil including the soft soil at the bottomof the hole is poured into the bag as well.

    9) Having the valve closed turn the gallon +

    cone upside down and place the cone in thecenter hole of tray and open the valve.

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    10.After flow of sand stops close the valve and

    pick the assembly up.

    11.Weigh of plastic Gallon + Cone + Sand,

    (after use).

    Get The Volume of the hole () :

    = (- - )"

    = ()/ (sand)

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    12) Measure the weigh the evaporating dish,

    .

    13) Weigh the evaporating dish + wet soil fromthe field, .

    14) Put the evaporating dish + wet soil in the

    oven and after 24hrs weigh it again,.15) Having the information you got so far in the

    table, Calculations can be carried out easily.

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    Dry unit weight in the field :(in-situ soil)= [] / [1+ ]

    (in-situ soil) = (- ) /

    (%) = () / ()*100

    where ,= (- )

    = (- )

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    Field compaction

    Compaction by rolls.

    Compaction by rammers.

    Compaction by vibration.

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    Compaction by rolls

    Smooth wheel rollers

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    Compaction by rolls

    Sheep's foot rollers

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    Compaction by rammers

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    How to choose thesuitable method

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    Relative compaction

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    Relative Compaction

    Relative compaction is a way of comparing

    compaction on the construction site with the

    laboratory compaction results.

    It is defined as:

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    References

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    References

    Engineering Properties of Soils Based on

    Laboratory Testing Prof. Krishna Reddy, UIC.

    Dr. El-Sayed Abdel Fatah El- Asaby (2006)SoilEngineering Technology Soil Mechanics,

    4thedition.

    Study report on compaction equipment andconstruction machinery,Report No. GE- R-76.

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