IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 05, 2016 | ISSN (online): 2321-0613
Shear Strength Improvement of sandy Soil using Coconut Fibre Vijay Shrivastava1 Urvi Upaddhaya2 Abhishek Tiwari3 Resident Engineer 2Structural Engineer 3Assistant Professor 1,2,3 Department of Computer Science and Engineering 1 MSV International INC India 2Becon, Bhopal 3Corporate Institute of Technology 1
Abstract— Shear strength is most important property of soil. It depends on particle interaction. Shear failure of soil occurs when particle slides over each other. When it comes to sandy soil then concern for shear strength increases, as the particles in sandy soil have only frictional force in between them. There is no cohesive force in between particles of sandy soil. The aim of this work is to investigate the variation in shear strength by adding coconut fiber. Coconut fibers are of brown color and are also known as coir fibre obtained from the outer shell of coconut. It is a waste material which can be utilized as a reinforcing material for soil. In this experiment 20 mm long coconut fibre are used to reinforce sandy soil and shear strength is evaluated by direct shear test. The result shows that there is 29% increment in shear strength parameter of sandy soil by adding coconut fibre. Key words: Sandy Soil, Shear Strength Parameter, Internal Friction, Coconut Fibre, Direct Shear
Tenacity 10.0 Breaking elongation 30% Diameter .1mm-.5mm Modulus of Rigidity 1.8924 dyne/cm² Swelling in water 30% Table 2: General Physical Properties of Coconut Fibres II. MANUFACTURING OF COCONUT FIBRES The process of manufacturing of coconut fibres involves three major steps-husking, retting and extraction of fibres. Husking involves the separation of the husk from the harvested fruits. To obtain good quality coir, the fruits are harvested when still green.
I. INTRODUCTION Soil is an important part of any big or small structure. The soil layer transfers the whole load to the soil layer beneath it. Therefore analyzing strength of soil has become an essential field of study. There are various ways to reinforce soil like using geotextiles, earth reinforcement etc. But these ways involves use of new and fresh material. Keeping sustainable development in mind use of waste materials has to be incorporated in studies. Among all other properties of soil shear strength is the most important. The use of coconut fibres can prove to be a highly efficient means of soil reinforcement. There are two types of coconut fibre brown fibres and white fibres. Mature coconut gives brown fibre while the white fibres are obtained from immature coconuts. In this paper use of brown fibres is focused as these are thick, coarse, strong, durable and have high abrasion resistance. Also, the use of coconut fibres can be particularly advantageous to India because of the widespread cultivation of coconut in the country. India has a rich cultivation of coconut, and if the fibres obtained from such high degree of cultivation can be put to use for reinforcing of soil, it shall prove to be a highly economic measure of strengthening of soil and with high degree of efficiency. Following tables illustrate the general properties of coconut fibres:
Component Percentage Lignin 45 Cellulose 40 Hemi-cellulose 0.50 Pectin and related compound 3.00 Ash 3.33 Table 1: Chemical Composition of Coconut Fibre Property Specifications Length 20-25 mm Density 1.4 g/cc
Fig. 1: Husking of Coconut Fibres It is then followed by retting, which is essentially a curing process. The husks are kept in an environment that encourages microbial action, which leads to decomposition of the pulp of the husk that allows it to be separated into coir fibres and coir pith. For fresh water retting, ripe husks are buried in pits along riverbanks, immersed in water filled concrete tanks or suspended by nets in a river, for a soaking period of about six months. For salt water retting, green husks are soaked in salinated fresh water, for a period of eight to ten months.
Fig. 2: Retting of Coconut Fibres Retting is followed by the extraction of fibres. The husks are taken out of water and washed. The outer skin is peeled off, placed on wooden blocks and beaten for separating the fibres from the pith. After this separation, fibres are cleaned and dried, with occasional beating and
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Shear Strength Improvement of sandy Soil using Coconut Fibre (IJSRD/Vol. 4/Issue 05/2016/320)
tossing to remove any impurities remaining in contact with the fibres.
percentages, from which the values of maximum shear stress were obtained. Then angle of internal friction was determined in each case from the relationship of maximum shear stress and normal stress. A final relationship between the angle of internal friction and fibre content was deduced, from which the maximum value of angle of internal friction and the corresponding optimum fibre content was obtained. A. Unreinforced Sand:
Fig. 3: Extraction of Coconut Fibres III. METHODOLOGY A. Collection of Material: 1) Soil Sample The sample used for this research work is sand. Sieve analysis, as per the provisions of IS 383-1970 provided that the sample belongs to Zone II, having a Fineness Modulus of 3.25. 2) Coconut Fibre: For the purpose of this work, the coconut fibers used were taken in finite lengths of 15 mm. The fibbers were extracted from the outer shell of the coconut, soaked in water and then dried under the sun. As the required quantity of fibers was less, hence shorter time period of soaking and drying was utilized, as compared to that of large scale manufacturing process. Following are the properties of the coconut fibbers that have been used for this research work: Coconut fibers from coconut shell are properly soaked in water and dried in sunrays. 20 mm long fibers are taken for this experimental work. Properties of coconut fibers are as follows: Property Specifications Length 20mm Density 1.6g/cc Diameter 0.1mm-1.5mm Major proteins present Lignin, Cellulose Modulus of Rigidity 1. 9248 dyne/cm² Table 3: Properties of Coconut Fibres used B. Diect Shear Test: Direct shear tests were performed on the soil sample. The initial results shown by the specimen without any reinforcing materials, at normal stresses of 0.5, 1.0 and 1.5 kg/cm² was first obtained. Next, direct shear test was performed using coconut fibre as reinforcement at 1.0%, 2.0% and 3.0% by weight of soil. The fibres were randomly mixed with the soil specimen. After the test has been performed, the stress-strain curves are plot for every individual situation and at every value of normal stress, from which the maximum shear stress was determined in each case. This was followed by graphs of maximum shear stress and normal stress to determine the value of angle of internal friction in each case. The variation of angle of internal friction with fibre content was studied and the optimum fibre content required was evaluated.
Fig. 4: Stress-strain relationship for unreinforced sand Figure 4 shows the stress-strain relationship for unreinforced soil. The maximum value of shear stress are 0.35 kg/cm², 0.60kg/cm² and 0.93 kg/cm² at normal stresses of 0.5 kg/cm², 1.0 kg/cm² and 1.5 kg/cm² respectively. The relationship between the maximum shear stress and normal stress for unreinforced soil gives the angle of internal friction obtained is 33.27ᵒ. B. Reinforced Sand: 1) Sand Reinforced At 1% By Weight:
Fig. 5: Stress-strain relationship for sand reinforced at 1% by weight Fig 5 shows the stress-strain relationship when sand is reinforced at 1% by weight. The maximum value of shear stress are 0.28 kg/cm², 0.67 kg/cm² and 1.10 kg/cm² at normal stresses of 0.5 kg/cm², 1.0 kg/cm² and 1.5 kg/cm² respectively. The internal friction obtained by relationship between shear stress and normal stress for reinforced soil is 35.64o.
IV. RESULTS The stress-strain relationship then compared for soil without reinforcement and with reinforcement with various
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Shear Strength Improvement of sandy Soil using Coconut Fibre (IJSRD/Vol. 4/Issue 05/2016/320)
2) Sand Reinforced At 2% By Weight:
The maximum angle of fiction is obtained for sand reinforced by 2% weight which is 40.79o. V. CONCLUSION In this paper effect of reinforcing sandy soil with coconut fiber has been analyzed. The results show that at 2% of fiber reinforcement by weight gives the optimum value of shear reinforcement. Beyond 2% of reinforcement of fibre by weight, there is reduction in internal friction. Thus it can be concluded that coconut fiber can be used to reinforce sandy soil to increase its shear strength. REFERENCES
Fig. 6: Stress-strain relationship for sand reinforced at 2% by weight The maximum value of shear stress are 0.39 kg/cm², 0.75 kg/cm² and 1.25 kg/cm² at normal stresses of 0.5 kg/cm², 1.0 kg/cm² and 1.5 kg/cm² respectively. The internal friction obtained by relationship between shear stress and normal stress for reinforced soil is 40.79o. 3) Sand Reinforced At 3% By Weight:
Fig. 7: Stress-strain relationship for sand reinforced at 3% by weight. Figure 8 shows the stress-strain relationship for sand reinforced at 3% by weight, The maximum value of shear stress are 0.37 kg/cm², 0.75 kg/cm² and 1.18 kg/cm² at normal stresses of 0.5 kg/cm², 1.0 kg/cm² and 1.5 kg/cm² respectively. The internal friction obtained by relationship between shear stress and normal stress for reinforced soil is 38.46o. C. Optimum Fibre Content:
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Fig. 8: Variation of angle of internal friction with percentage of fibre content
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