soil compaction (group 4)

INTRODUCTION TO COMPACTIONCOMPACTION TESTFACTORS AFFECTING COMPACTIONCONTROL OF COMPACTIONFIELD COMPACTION EQUIPMENT & THEIR SUITABILITY

Owais muneer (27)

Compaction means pressing of the soil particles close to each other by mechanical methods.

Air is expelled from soil mass and mass density is increased.

It is done to improve the engineering properties Like shear strength, stability etc…

Reduces compressibility and permeability.

The degree of compaction of soil is measured in terms of dry unit weight.

Owais muneer

(27)

Owais muneer

(27)

STANDARD PROCTOR TEST

A standard volume(944 cc or 1/30 cft mould) is filled up with soil in 3 layers. Each layer is compacted by 25 blows of a standard hammer of weight 2.495 kg, falling through a height of 304.8 mm(12 inch). The weight of the compacted soil & its water content(w) is determined & the dry unit weight of the soil is calculated as :

y(t)= weight of compacted soil/volume of the mould

y(d)= Y(t)/1+w pradeep kaushik

(28)

STANDARD PROCTOR TEST

The test is repeated at different water contents. The dry unit weight of each compacted sample is plotted against the water contents. The curve so obtained is called is compaction curve.

Pradeep kaushik (28)

COMPACTION -PROCEDURES

1 2

3

4

5

Pradeep kaushik

(28)

OPTIMUM MOISTURE CONTENT (OMC)

The peak point of the compaction curve corresponds to the maximum dry unit weight, y(d)max.

The water content corresponding to the maximum dry unit weight is known as the optimum moisture content (OMC).

Pravin mahto (29)

WATER CONTENT

COMPACTIVE EFFORT

TYPE OF SOIL

METHOD OF COMPACTION

Pravin mahto (29)

At low water contents, the soil is stiff & the soil grains offer more resistance to compaction.

As the water content increases, the particles develop larger & larger water films around them, which tend to lubricate the particles & make them easier to be worked around, to move closer into a denser configuration, resulting in a higher dry unit weight & lower air voids.

Pravin mahto

(29)

As the compactive effort increases,

the maximum dry unit weight of compaction increases

The optimum moisture content decreases to some extent

Purushottam kumar

(30)

Fine grain soil

needs more water

to reach optimum;

and

coarse grain soil

needs less water

to reach optimum.

.

Compaction curves for different soils with the same

compactive effort ,fine grain soil needs more water to reach

optimum and coarse grain soil needs less water to reach

optimum.Purushottam kumar (30)

The mode of compaction influence some what the shape and the position of the dry unit weight v/s water content plot.

Purushottam kumar

(30)

Field verification tests of achieved compaction

can be conducted by any of several accepted

methods:

1) Sand cone

2) Balloon

3) Nuclear

Rahul (31)

The first two methods are destructive tests. They involve

excavating a hole in the compacted field and weighing the excavated material.

determining the water content of theexcavated material.

measuring the volume of the resultinghole.

Rahul (31)

Disadvantages of using sandcone and balloon methods:

1) time-consuming to conduct sufficient tests for statistical analysis.

2) problems with oversized particles.

3) the determination of water content takes time

Rakesh ranjan (32)

NUCLEAR COMPACTION TEST

Nuclear methods are used extensively to determine the water content and density of soils.

The instrument required for this test can be easily transported to the fill, placed at the desired test location, and within a few minutes the results can be read directly from the digital display.

. Rakesh

ranjan (32)

Advantages of the nuclear method when compared with other methods include thefollowing:

1) Decreases the time required for a test from as much as a day to a few minutes, thereby eliminating potentially excessive constructiondelays.

2) It is nondestructive in that it does not require the removal of soil samples from the site of the tests. Rezwan ahmad

(33)

3) Provides a means of performing density tests on soils containing large-sized aggregates and on frozen materials.

4) Reduces or eliminates the effect of the personal element, and possible errors. Erratic results can be easily and quickly rechecked.

Rezwan ahmad

(33)

Disadvantages of the nuclear method when compared with other methods include thefollowing:1) Nuclear test instruments, if not used properly,

present a potential source of radiation that can be harmful to humans.

2) These instruments usually require a skillful operator who exercises care to ensure that no harm can result from the use of the instruments.

3) In the U.S., a license is required to possess,

own, or use nuclear type instrumentsRohit kumar (34)

Type Of Equipment Suitability For soil type

Rammers or Tampers All Soils

Smooth wheeled rollers Crushed Rocks, sand,gravel

Pneumatic tyred rollers Gravel, silts,clayey soil,sand

Sheepsfoot rollers Clayey soil

Vibratory rollers Sands Rohit kumar (34)

Type Of Equipment Nature Of Project Rammers Or Tampers In confined areas e.g.trench fills

Smooth wheeled rollers Road construction

Pneumatic tyred rollers Base & sub-base for highways

Sheepsfoot rollers Core of earth dams

Vibratory rollers Embankment for oil storage tank

Rohit kumar

(34)