Grameen Sampark Final April 0... - pmgsy

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22 Stabilization of Soil Subgrade with Polypropylene Fibres Dr. I.K.Pateriya* and Dr. K. A. Patil** In India, transportation is mainly by roads. Only roads can access very small villages, remote areas and hilly areas. Hence, considerable attention is required towards the widening of roads, their suitability and periodic repair works. Most state highways in the central part of India have problems of foundation for highway embankments, bridge abutments, retaining walls and earth dams with steep slopes have been built using different types of reinforcements. Hoare(1979) analyzing the results of a series of laboratory compression and CBR tests on a sandy gravel reinforced with randomly distributed synthetic fibres less than 2% by weight, observed that the presence of fibres increased the apparent angle of internal friction and ductility of the soil particularly at low confining stress. A. Boominathan (1999) carried out some tri-axial compression tests on sand reinforced with randomly distributed fibres. *Joint Director (Technical), NRRDA, Delhi **Lecturer in Civil Engineering; Govt. College of Engineering, Karad (M.S.) 415 124 Grameen Sampark Fibre reinforcement technique permits use of natural as well as synthetic fibres for soil reinforcement. In Maharashtra black cotton soil is found in abundance which is highly expansive soil. An attempt has been made to investigate the use of polypropylene fibres for improving properties of locally available soil. The comparison of properties of soil with addition of varying percentages of fibres by dry weight of soil and having different aspect ratios is also carried out. The addition of polypropylene fibres resulted in increase in optimum moisture content and decrease in maximum dry density. Direct shear tests conducted on soil shows increase in value of cohesion and decrease in value of angle of internal friction. With the inclusion of the fibres increase in C.B.R. value was observed. The crust thickness of flexible pavement is appreciably reduced, due to increase in C.B.R.value of soil subgrade.
EXPERIMENTAL WORK Materials Used The soil used in the study was collected from 10 km distance from Jalna. The soil used was black cotton soil. Table 1 shows geotechnical properties of soils collected for experimentation. Polypropylene fibres of average diameter 0.25 mm with aspect ratios of 20, 40 and 80 were used. Sample Preparation Fibre reinforced soil samples were prepared at maximum dry density and optimum moisture content obtained by conducting standard Proctor test on unreinforced soil and reinforced soil. The fibre reinforced specimens were prepared by hand mixing the dry soil, water and polypropylene fibres. The percentage of fibre used in samples was 1, 2, and 3 percent by dry weight of soil. The water was added prior to fibre to prevent floating problems. fibre reinforced soil samples were prepared at the maximum dry density and the optimum Table1: Geotechnical properties of soil Pradhan Mantri Gram Sadak Yojana moisture content obtained from standard proctor tests on reinforced soil. Un-drained direct shear tests were conducted on reinforced samples with varying percentages of fibres and aspect ratio. California bearing ratio (C.B.R) tests were conducted under soaked conditions. Unconfined compression strength tests were conducted on cylindrical specimen at Proctors maximum dry density and optimum moisture content. Specific Liquid Plastic Plasticity Maximum Dry Cohesion Angle of Internal Gravity Limit % Limit % Index % 3 Density (gm/cm ) 2 (kN/m ) Friction (Degrees) 2.49 56 27 29 1.53 34 16 RESULTS AND DISCUSSION The influence of aspect ratio and fibre concentration on the properties of soil were studied. The OMC and dry density test results on black cotton soil with different aspect ratio and fibre content are reported in Table 2. These data indicate that maximum dry density decreases gradually with increase in the fibre content, which is due to lower density of the fibre than the soil particles. An increase in Optimum moisture content was observed due to adsorption of water particles on the surface of polypropylene fibres. Table 2: Proctor's test results for un-reinforced and reinforced soil Sr. No. Description Aspect Ratio % O.M.C MDD (gm/cm3) 1. Soil without reinforcement - 24.6 1.53 2. Soil with 1 % Polypropylene fibres 20 24.7 1.52 3. Soil with 2 % Polypropylene fibres 20 24.9 1.51 4. Soil with 3 % Polypropylene fibres 20 25.1 1.50 5. Soil with 1 % Polypropylene fibres 40 24.8 1.52 6. Soil with 2 % Polypropylene fibres 40 25.0 1.50 7. Soil with 3% Polypropylene fibres 40 25.3 1.48 8. Soil with 1 % Polypropylene fibres 80 24.9 1.50 9. Soil with 2 % Polypropylene fibres 80 25.2 1.47 10. Soil with 3% Polypropylene fibres 80 25.4 1.44 Grameen Sampark 23
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 24 and 25: 24 Changes in Cohesion and Direct
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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