Grameen Sampark Final April 0... - pmgsy

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24 Changes in Cohesion and Direct shear tests were conducted on soil samples in unreinforced and reinforced conditions. The Grameen Sampark reinforcement was added in the range of1%to3%with varying aspect ratios of 20, 40 and 80. The results obtained are summarized in Table 3. Table 3: Effect of reinforcement on shear strength characteristics of soil Sr. No. Description Aspect Cohesion Increase over Ratio 2 (kN/m ) % Soil without Reinforcement (Degrees) 1. Soil without reinforcement - 34 — 16 2. Soil with 1 % Polypropylene fibres 20 35.4 4.12 15.9 3. Soil with 2 % Polypropylene fibres 20 37.2 9.42 15.6 4. Soil with 3 % Polypropylene fibres 20 36.9 8.53 15.5 5. Soil with 1 % Polypropylene fibres 40 36.3 6.76 16.0 6. Soil with 2 % Polypropylene fibres 40 39.6 16.47 15.8 7. Soil with 3 % Polypropylene fibres 40 38.7 13.82 15.6 8. Soil with 1 % Polypropylene fibres 80 35.8 5.29 15.7 9. Soil with 2 % Polypropylene fibres 80 38.4 12.94 15.4 10. Soil with 3 % Polypropylene fibres 80 37.9 11.47 15.0
From Table 1, it is found that black cotton soil has 2 cohesion (C ) as 34 kN/m and angle of internal friction ( ) as 16 degrees. From Table 3, it is found that due addition of polypropylene fibres in black cotton soil, for all aspect ratios of 20, 40 and 80, the cohesion increases and the angle of internal friction decreases. Due to addition of 2% polypropylene fibres in black cotton soil, the cohesion increases by 9.42%, 16.47% and 12.94% for aspect ratio of 20,40 and 80 respectively. The angle of internal friction decreases by 2.5%, 1.25% and 3.75% for aspect ratio of 20, 40 and 80 respectively. Fibre content and aspect ratio governs the shear strength of fibre reinforced soil. The strength of reinforced soil increases with an increase in fibre content. The rate of increase is higher at lower fibre content i.e. less than 2%. At fibre content greater than 2%, the relative gain in Pradhan Mantri Gram Sadak Yojana strength is small. This is possibly due to the fact that fibres of lower specific gravity occupy relatively large volume in the composite. Thus, with higher fibre content, the quantity of soil matrix available for holding the fibres is insufficient to develop an efficient bond between soil and fibre. above 2% fibre content, the uniform mixing of soil and fibre is difficult as balling up of fibre takes place. Changes in CBR value of soil Table 4: CBR values for reinforced and un-reinforced soil The CBR tests were conducted on un-reinforced soil and soil reinforced with fibre. The tests were carried out after four days soaking in water. CBR values at different aspect ratio and varying fibre content are given in table 4 and Fig. 1. The maximum CBR value in present study was found at aspect ratio of 40 and 2% fibre content. Sr.No. Description Aspect Ratio Soaked CBR % Value (%) increase 1. Soil without reinforcement - 3.05 —- 2. Soil with 1 % Polypropylene fibres 20 4.20 37.77 3. Soil with 2 % Polypropylene fibres 20 5.15 68.85 4. Soil with 3 % Polypropylene fibres 20 5.05 65.57 5. Soil with 1 % Polypropylene fibres 40 4.50 47.55 6. Soil with 2 % Polypropylene fibres 40 5.35 75.40 7. Soil with 3 % Polypropylene fibres 40 5.20 70.49 8. Soil with 1 % Polypropylene fibres 80 4.40 44.26 9. Soil with 2 % Polypropylene fibres 80 5.15 68.85 10. Soil with 3 % Polypropylene fibres 80 5.00 63.93 From Table 3, it is found that due addition of 2 % polypropylene fibres in black cotton soil, the increase in C.B.R. value is found to be 47.55%, 75.40 % and 70.49 % for aspect ratio of 20, 40 and 80 respectively. Also, it is observed that on 3% addition of polypropylene fibres, C.B.R. value is found to be less than that at 2% fibre content. Hence, 2 % fibre content with aspect ratio of 40 may be considered as optimum fibre content. Grameen Sampark 25
Page 2 and 3: In this Issue Editorial 3 Potential
Page 4 and 5: 4 Potential Applications of Interlo
Page 6 and 7: 6 Interlocking Concrete Block Pavem
Page 8 and 9: 8 materials used for production of
Page 10 and 11: 10 Construction of Sub grade This i
Page 12 and 13: 12 Typical Pavement Compositions Ty
Page 14 and 15: 14 Guidelines for the use of In
Page 16 and 17: 16 layers due to repeated applicati
Page 18 and 19: 18 Subgrade Failure Criterion The b
Page 20 and 21: 20 A maximum of 50mm rut depth was
Page 22 and 23: 22 Stabilization of Soil Subgrade w
Page 26 and 27: 26 Increase in the C.B.R. value is
Page 28 and 29: 28 Laboratory Test (Under Vertical
Page 30 and 31: 30 Apart from the above, both faces
Page 32: News in Brief General Body Meeting

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