soil compaction.pdf

8/12/2019 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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