mid sem report final

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SWELL POTENTIAL OF AN EXPANSIVE SOIL STABILIZED WITH POLYPROPYLENE FIBRE 1. General Expansive soils exhibit volume changes due to variation in moisture content. Expansive soils are spread over a large area of the world. These soils exhibit large swelling and shrinkage due to environmental and seasonal moisture changes resulting in soil movement which seriously damages many structures built on them. There is, therefore, a need to study the problems associated with these soils. 2. Occurrence of Expansive Soils Expansive soils are found in many regions of the world, particularly in arid and semi-arid regions and also where wet conditions occur after prolonged periods of drought. Their distribution is dependent on geology (parent material), climate, hydrology, geomorphology and vegetation. Shrinkage cracks develop in soils during the dry season due to stifling heat of the tropics. During rainy season, the expansive clay minerals attract a great amount of water, mainly through shrinkage cracks, resulting into massive change in volume. Swelling clays are detected in Australia, Canada, China, Jordan, Saudi Arabia, India, South Africa, Sudan, Egypt, and the United States. 1

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Page 1: Mid Sem Report Final

SWELL POTENTIAL OF AN EXPANSIVE SOIL STABILIZED

WITH POLYPROPYLENE FIBRE1. General

Expansive soils exhibit volume changes due to variation in moisture content.

Expansive soils are spread over a large area of the world. These soils exhibit large

swelling and shrinkage due to environmental and seasonal moisture changes resulting

in soil movement which seriously damages many structures built on them. There is,

therefore, a need to study the problems associated with these soils.

2. Occurrence of Expansive Soils

Expansive soils are found in many regions of the world, particularly in arid and semi-

arid regions and also where wet conditions occur after prolonged periods of drought.

Their distribution is dependent on geology (parent material), climate, hydrology,

geomorphology and vegetation. Shrinkage cracks develop in soils during the dry

season due to stifling heat of the tropics. During rainy season, the expansive clay

minerals attract a great amount of water, mainly through shrinkage cracks, resulting

into massive change in volume. Swelling clays are detected in Australia, Canada,

China, Jordan, Saudi Arabia, India, South Africa, Sudan, Egypt, and the United

States.

Swelling soils in India are inorganic clay of medium to high plasticity. They are

found in different areas of Maharashtra, western parts of Madhya Pradesh, parts of

Andhra Pradesh, parts of Gujarat, and some parts of Tamil Nadu. They are known as

black cotton soils. The name is derived from the fact that cotton grows well in the

black soil. A majority of them plot above A-line on the plasticity chart. The clay

mineral is predominantly montmorillonite or a combination of montmorillonite and

illite. These soils are usually recognized in the field by their fissured or shattered

condition or by obvious structural damage caused by them to existing buildings. On

account of high swelling and shrinkage potential these are difficult soils to deal with

in foundation design.

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3. Scope of Present Work

Construction activities on expansive soils require stabilization of soil prior to the start

of work. Soil stabilization is the process of improving the engineering properties of

the soil and thus making it more stable.

In the recent years, the research on fibre reinforced soils has demonstrated that this

material might be a practical and cost effective technique for reinforcement of

subgrade soils. Polypropylene is an economical material that offers a combination of

outstanding physical, chemical, mechanical, thermal and electrical properties not

found in any other thermoplastic.

In the present work, effect on swell behaviour is proposed to be studied for an

expansive soil treated with different percentages of polypropylene fibre by conducting

a series of one-dimensional consolidation tests for measurement of swell pressure.

4. Materials and Testing Programme

Materials used

Soil used

Soil to be used in the experiments has been collected from a village near Mouda

located in Nagpur (Maharashtra). The soil is classified as medium compressible clay,

CH, as per IS: 1498 (1970).

Polypropylene fibre

Polypropylene fibre has been procured from Shivananda Marketing Pvt. Ltd., Ansari

Road, Daryaganj, New Delhi. Polypropylene fibre has been divided into two

categories on the basis of size (6mm and 12mm) for its inclusion in various

percentages (0.05, 0.1, 0.15, 0.2, & 0.25 %) by dry weight of the parent soil. The

specific gravity of polypropylene fibre varies from 0.90 to 0.91, value as obtained

from the manufacturer. Its alkaline strength is very good as reported by the

manufacturer. The physical properties of polypropylene fibre as obtained from

manufacturer are given in Table.

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Physical properties of Polypropylene Fibre

S. No. Property Description

1. Shape Triangular

2. Cut length 6mm, 12mm

3. Effective Diameter 25-40µm

4. Specific Gravity 0.90-0.91

5. Melting Point 160-165oC

6. Tensile Strength 320-490 MPa

7. Young’s Modulus > 4000 MPa

Standard Proctor Tests

Standard Proctor tests will be conducted to determine optimum moisture content and

maximum dry density of parent soil and soil mixed with polypropylene fibre of two

sizes. These tests will be conducted in order to prepare specimens at maximum dry

density by adding desired optimum moisture content as per specifications of IS: 2720

(Part 7) (1974).

Swell Tests

Samples, 10cm diameter, 2.5 cm thick will be prepared in a purpose-made

compaction unit containing the consolidometer ring at the required dry unit weight

and optimum water content determined from the compaction tests. After compaction,

samples are transferred to the consolidometer and the swell tests are performed.

Specimen are inundated and allowed to swell freely under a seating load of 0.06

kg/cm2 until primary swell is complete. Thereafter, the specimens are loaded until the

initial void ratio is obtained. The swelling pressure is taken as the pressure that brings

the sample back to its initial height.

5. Field Applications

Applications that aim to achieve increased soil strength by mixing fibres into soil are

the following:

(a) Repair of local slope failures with a re-compacted mixture of fibres and soil.

(b) Embankment construction with steeper slopes.

(c) Minimization of expansion-contraction cracks.

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(d) Mechanical stabilization of subgrade.

(f) Fibre-reinforced soils are currently being used to recycle and reuse shredded and

fibrous inorganic wastes in engineering applications and as alternate backfills and

improved pavement materials.

6. Advantages of Polypropylene Fibre Reinforced Soil

(a) Increased shear strength with maintenance of strength isotropy.

(b) Beneficial for all type of soils (i.e. sand, silt and clay).

(c) Reduce post peak strength loss.

(d) Increased ductility.

(e) Increased seismic performance.

(f) No catastrophic failure.

(g) Great potential to use natural or waste material such as coir fibers, shredded tire and recycled waste plastic strips and fibers.

(h) Provide erosion control and facilitate vegetation development.

(i) Reduce shrinkage and swell pressure.

(j) No appreciable change in permeability.

(k) Unlike lime, cement and other chemical stabilization methods, the construction

using fiber reinforcement is not significantly affected by weather conditions.

(l) Fiber-reinforcement has been reported to be helpful in eliminating the shallow

failure on the slope face and thus reducing the cost of maintenance.

7. Disadvantages of Polypropylene fiber reinforced soil

(a) Lack of good interfacial adhesion

(b) Quality variations due to change in climate, location, weather conditions, soil

characteristics.

(c) Low thermal stability

(d) Poor compatibility

(e) Low modulus

8. Expected Results

1. Reinforcing expansive soils with fibre will decrease the maximum dry density and

increase the optimum water content of the soil.

2. Synthetic fibre is useful in restraining the swelling tendency of expansive soils. As4

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the fiber content increased, both the swell potential and the swelling pressure of

expansive soil decrease.

9. References

1. IS: 1498 (1970), “Indian Standard Methods of Test for Soils: Classification and

Identification of Soil for General Engineering Purposes”, Bureau of Indian

Standards.

2. IS: 2720 (Part 7) (1974), “Indian Standard Methods of Test for Soils:

Determination of Moisture Content-Dry Density Relation using Light

Compaction”, Bureau of Indian Standards.

3. IS: 2720 (Part 15) (1986), “Indian Standard Methods of Test for Soils:

Determination of Consolidation Properties”, Bureau of Indian Standards.

4. Gopal Ranjan, R. M.Vasan and H.D. Charan (June 1996),” Probabilistic

analysis of randomly distributed fiber-reinforced soil” Journal of Geotechnical

Engineering, Vol. 122, No.6, June, 1996, Paper No. 9546.

5. Bijayananda Mohanty, Mahipal Singh Chauhan & Satyendra Mittal (Dec.2011),”

California bearing ratio of randomly oriented fiber reinforced clayey subgrade for

rural roads” Proceedings of Indian Geotechnical Conference December 15-17,

2011, Kochi (Paper No. J-354), pp. 611-614.

6. S. Twinkle & M. K. Sayida (Dec.2011),” Effect of polypropylene fibre and lime

admixture on engineering properties of expansive soil” Proceedings of Indian

Geotechnical Conference December 15-17, 2011, Kochi (Paper No.H-

085),pp.393-396.

7. Venkata Koteswara Rao Pasupuleti, Satish Kumar Kolluru, Blessingstone

T(July2012),” Effect of Fiber on Fly-Ash Stabilized Sub Grade Layer Thickness”

International Journal of Engineering and Technology (IJET) ,Vol. 4 ,No 3 ,Jun-Jul

2012, pp.140-147.

8. Rabindra Kumar Kar, Pradip Kumar Pradhan , Ashutosh Naik(2012),”

Consolidation Characteristics of Fiber Reinforced Cohesive Soil” EJGE Vol. 17

(2012), Bund. Z, pp.3861-3874.

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9. Mona Malekzadeh & Huriye Bilsel(2012),” Swell And Compressibility of Fiber

Reinforced Expansive Soils” International Journal of Advanced Technology in

Civil Engineering, ISSN: 2231 –5721, Volume-1, Issue-2, 2012, pp.42-46.

10. Mona Malekzadeh, Huriye Bilsel (2012),” Effect of Polypropylene Fiber on

Mechanical Behaviour of Expansive Soils” EJGE Vol. 17 (2012), Bund. A, pp.

55-63.

11. Shivanand Mali and Baleshwar Singh (2014),” Strength Behaviour of Cohesive

Soils Reinforced with Fibers” International Journal of Civil Engineering Research,

ISSN 2278-3652 Volume 5, Number 4 (2014), pp. 353-360.

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