Effects of Alternate Wetting and Drying on CBR of Coir Fibre Reinforced Black Cotton Soil

IJSTE - International Journal of Science Technology & Engineering | Volume 3 | Issue 05 | November 2016 ISSN (online): 2349-784X

Effects of Alternate Wetting and Drying on CBR of Coir Fibre Reinforced Black Cotton Soil Stuti Maurya Assistant Professor Department of Civil Engineering REC, Azamgarh

Abstract Stability of any structure depends on behavior of soil under it. In case of construction in soft soil, ground improvement by soil stabilization or soil reinforcement is usually adopted. Many organic natural fibers like rice husk, sisal, jute, bamboo, palm fibre and coir fibre etc. are used for stabilization purposes and different engineering properties are determined like liquid limit, plastic limit, specific gravity, OMC, MDD, UCS, CBR etc. The coir fibre being biodegradable material will decay under extreme environmental conditions such as polluted water, contact with leachate, cycles of wetting and drying, cycles of freezing and thawing and so on. In general, life of coir fibre in soil is expected to be 8-10 years. Therefore under different environmental conditions it may degrade fast. The gain in soil strength or decrease in swelling might be lost. This aspect is not studied so far.

Hence in this work this is attempted.

Keywords: Black Cotton (BC), California Bearing Ratio (CBR), Optimum Moisture Content (OMC), Maximum Dry Density (MDD), Clay of Medium Plastic (CI) ________________________________________________________________________________________________________ I.

INTRODUCTION

Keeping in mind the large geographical area of India (3,287,240 sq. km) and population of India (125 million approx.) a vast network of structures and roads are required (Singh and Mittal, 2014). The land available for construction purposes is very less because of increasing modernization and urbanization. Owing to this, these days construction of structures is being carried on land with weak or soft soil. Now, stability of any structure will depend on the properties of soil. For using land with soft soil in construction purposes, requires ground improvement techniques like soil stabilization and soil reinforcement. Most of the soil available is such that they have good compressive strength, adequate shear strength but are weak in tension or having poor tensile strength. To overcome this, many researchers have used natural materials such as Jute, coir, sisal, rice husk and bamboo, as reinforcing materials in soil. Fibre reinforced soil is seen to be effective in all types of soils (i.e. sand, silt and clay). (Chapale and Dhatrak, 2013). Main advantages of these materials are that they are locally available and very cheap. Being biodegradable they do not create disposal problems in the environment. (Singh and Bagra, 2013).During the last 25 years, much work has been done on strength behaviour of fibre reinforced soil and has been established beyond doubt that addition of fibre in the soil improves the overall engineering performance. Degradation behavior of fibre yet to be studied under different environmental conditions like alternate wetting and drying, freezing and thawing, effects of acid rain, effect of leachate. Coir fiber is a strongest natural fiber, so the degradation of randomly distributed coir fiber is checked in this study by alternate wetting and drying in terms of CBR value. The California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and base courses. Subgrade is a very important part to support all construction loads on it. To determine the effects of different environmental conditions (alternate wetting and drying in water, acid) a series of experiments are carried out on expansive soil sample with 1% of randomly distributed coir fibre of 35mm in length. As a reference for making comparison, the above said tests are also carried out for unreinforced soil sample.

II. MATERIALS USED Black Cotton Soil The black cotton soil sample was collected from MANIT, Bhopal campus. The properties are given in table 1.

Table – 1 Black cotton soil Liquid Limit 49.83% Plastic Limit 23.80% Plasticity Index 26.03% Specific Gravity 2.66 % Fines 89.33 % Soil Classification CI

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Effects of Alternate Wetting and Drying on CBR of Coir Fibre Reinforced Black Cotton Soil (IJSTE/ Volume 3 / Issue 05 / 008)

OMC MDD CBR(unsoaked) CBR(soaked)

16.97% 18.66kN/m3 8.32 2.84

Coir Fibre Coir geotextile was collected from Geology Lab, MANIT, Bhopal. It was cut into 35mm size and coir fibers are separated from geotextile. The fibre was then distributed randomly in the soil for experimental purpose. The properties of coir fibre are given in table 2. The coir fibre was mixed in black cotton soil in varying proportions. The various proportions in which coir fibre was mixed were 0.25%, 0.5%, 0.75% and 1%. Maximum strength was observed when 1% coir fibre was mixed in soil. This soil fibre mix was subjected to alternate wetting and drying in water and sulphuric acid. So, in the current study, degradation of coir fibre under multiple cycles of wetting and drying was studied.

Table – 2 Properties of coir fibre Property Value Length 35 mm Diameter 0.45 – 0.5 mm Tensile Strength 11 – 25 N/mm2

Fig. 1: Coir Geotextile

Fig. 2: Coir fibre used for soil stabilization

Sulphuric Acid Acid soaking was done to determine the effect of acid rain on CBR of black cotton soil with coir fibre and without coir fibre. The prepared CBR moulds with coir fibre and without coir fibre were soaked in N/50 sulphuric acid mixed in distilled water at the rate of 0.6 ml/5 L to bring the pH of solution to a value of 4.

III. TESTING PROCEDURE CBR Mould Preparation To prepare CBR mould, optimum moisture content and maximum dry density of the soil are determined by adopting heavy compaction. Each batch of 5.5 kg weight soil is mixed with 1% of randomly distributed coir fibre, water up to the optimum moisture content. The soil is divided into five equal parts; the soil is compacted in five equal layers, each by applying 56 evenly distributed blows of the 4.89 kg rammer.

Fig. 3: Mould after CBR Test All rights reserved by www.ijste.org

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Effects of Alternate Wetting and Drying on CBR of Coir Fibre Reinforced Black Cotton Soil (IJSTE/ Volume 3 / Issue 05 / 008)

Alternate wetting and drying in sulphuric acid For alternate wetting CBR moulds were kept in sulphuric acid of pH 2.5 for 24 hours and for drying purpose moulds are keep in oven at 500C for next 24 hours.

Alternate wetting and drying in water For alternate wetting CBR moulds were kept in water for 24 hours and for drying purpose moulds are keep in oven at 50 0C for next 24 hours.

IV. RESULTS AND DISCUSSIONS Effect of alternate wetting and Drying in sulphuric acid on CBR of Coir fibre reinforced BC Soil CBR mould of black cotton soil was prepared without coir fibre and with 1% of coir fibre. Prepared CBR Mould was kept in sulphuric acid with 0.6ml/5l of distil water for soaking purpose of 24 hours and for drying purpose it was kept in oven at 500C for 24 hours. The process of alternate soaking and drying was done for 7 days, 14 days and 28days. CBR value decreases with increase in time.

The liquid limit decreased for black cotton soil with increase in sulphuric acid concentration generally due to increase in electrolyte concentration of the pore fluid and consequent decrease in the thickness of double layer developed. This indicates the reduction in water holding capacity and increase in the frictional resistance and decrease in cohesion in soil. With increase in acid concentration the cation exchange capacity of soils decreases. There is a decrease in the optimum moisture content of soils.

Unconfined compressive strength has significantly reduced due to loss of cohesion. CBR value of BC soil decreases with increase in time.

Fig. 4: Variation in CBR of Black Cotton Soil without coir fibre after alternate wetting and drying in acid for different time periods

Fig. 5: Variation in CBR of Black Cotton Soil with coir fibre after alternate wetting and drying in acid for different time periods

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Effects of Alternate Wetting and Drying on CBR of Coir Fibre Reinforced Black Cotton Soil (IJSTE/ Volume 3 / Issue 05 / 008)

Alternate soaking and drying in water CBR mould of black cotton soil was prepared without coir fibre and with 1% of coir fibre. Prepared CBR Mould was kept in water for soaking purpose for 24 hours and for drying purpose it was kept in oven at 50 0C for 24 hours. The process of alternate soaking and drying was done for 7 days, 14 days and 28days. CBR value decreases with increase in time and the variations in CBR value with coir fibre and without coir fibre.

After a number of alternate wetting and drying cycles, black cotton soil starts losing its strength as compared to the initial strength. Bearing capacity increases with increase in alternate wetting and drying cycles but after few no of cycles the rate of increase of bearing capacity reduces drastically and thus there is reduction in the bearing capacity. Alternate wetting and drying cycle also affect the liquid limit and plastic limit of lateritic soil. Both liquid limit and plastic limit decreases with increase in the number of alternate wetting and drying cycles.

Fig. 6: Variation in CBR of Black Cotton Soil without coir fibre after alternate wetting and drying in water for different time periods

Fig. 7: Variation in CBR of Black Cotton Soil with coir fibre after alternate wetting and drying in water for different time periods

V. CONCLUSIONS In present work effect of different environmental conditions on CBR of fibre mixed black cotton soil has been studied. CBR mould of BC soil mixed with optimum coir fibre content and without coir fibres were prepared and were subjected to extreme environmental conditions like alternate wetting and drying in water, in sulphuric acid. The work conducted in this study can be summed up as the following:  Soaked CBR value of BC soil was 2.82. It increased by mixing coir fibres in random manner. The maximum gain in soaked CBR value was 3.72, increased by 31% at 1% coir fibres of 35mm lengths.  On alternate wetting and drying, degradation of coir fibre was much more in sulphuric acid than in water.

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Effects of Alternate Wetting and Drying on CBR of Coir Fibre Reinforced Black Cotton Soil (IJSTE/ Volume 3 / Issue 05 / 008)



On alternate wetting and drying in acid, CBR of stabilized soil and unstabilized soil decreases with increase in time but after 14 days and 28 days CBR was very less and decreased by 35% than original. So coir fibre is not useful for stabilization in acid rain prone areas.

REFERENCES

[1]

Chaple Parag M. and Dhatrak A. I. (2010). Performance of Coir fibre Reinforced Clayey Soil. The International Journal of Engineering and Science (IJES), Volume 2, Issue 4, pp 54-64.

[2] Dixit Savita and Verma Preeti (2012). The effect of surface modification on the water absorption behaviour of coir fibres. Advances in Applied Science Research, 3 (3):1463-1465, ISSN: 0976-8610.

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[4] Pillai Sudhakaran M. (2003). Ecofriendly plastics/remedial measures for environment sustailability, Coir Board Government of India. 4th International R&D conference for Water and Energy for 21st century, 28-31 January. Aurangabad.

[5] Sen Tara and Reddy H. N. Jagannatha (2011). Application of Sisal, Bamboo, Coir and Jute Natural Composites in Structural Upgradation. International Journal of Innovation, Management and Technology, Vol. 2, No. 3, June.

[6] Seracettin Arasan (2010). Effect of Chemicals on Geotechnical Properties of Clay Liners: A Review. Research Journal of Applied Sciences, Engineering and Technology 2(8): 765-775, ISSN: 2040-7467.

[7] Sharma Pankaj, Vyas Sameer, Mahure N. V, Pathak R.P., Vidyarthi U.S., Singh Devender and Sharma A (2012). Influence of acidic precipitation on physico-chemical and engineering properties of soil of medium plasticity from Assam. International Journal of Environmental Engineering Research, ISSN 2278–1331, Volume 1, Issue 1, 41-50.

[8] Singh H. P. and Bagra M. (2013). Improvement in CBR Value of Soil Reinforced With Jute Fibre. International Journal of Innovative Research in Science, Engineering and Technology, Vol. 2, Issue 8, August. ISSN: 2319-8753.

[9] Singh Mandeep and Mittal Anupam (2014). A Review On The Soil Stabilization With Waste Materials, International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622.

[10] Umesh T.S., Sharma H. D., Dinesh S. V., Sivapullaiah P.V. and Basim Swamy.C. (2011). Physico-Chemical changes in soil due to sulphuric acid contamination. Proceedings of Indian Geotechnical Conference. December 15-17, Kochi.

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