Grameen Sampark Final April 0... - pmgsy

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