Grameen Sampark Final April 0... - pmgsy

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Increase in the C.B.R. value is due to compaction
characteristics of polypropylene fibre reinforced soil.
Higher compaction can be achieved by addition of
fibres with higher aspect ratio up to certain limit. The
design of flexible pavement is governed by C.B.R. value
of subgrade soil. Thus, higher value of C.B.R. for
subgrade soil gives lesser pavement thickness and
proves to be the economical solution in pavement
construction.
% Soaked CBR Value
5.5
5
4.5
4
3.5
3
0 1 2 3
Polypropylene fibres Content
Figure 1: Relationship between polypropylene fibres
content and Soaked % C.B.R. value
Grameen Sampark
1 % fibres 2 % fibres 3 % fibres
Reduction in Crust Thickness of Flexible
Pavement
Thickness of flexible pavement is calculated based on
C.B.R. value of soil subgrade and traffic in terms of ESAL
applications as per SP:72-2007. As the C.B.R. value
increased from 3.05 % to 5.35 %, on addition of 2 %
polypropylene fibres with aspect ratio of 40, the crust
thickness reduces appreciably. Table 5 below, illustrates
the reduction in crust thickness for different ESAL
applications (Traffic categories T4 to T 7of SP 72:2007)
From table 5, it is observed that the design crust
thickness reduces by 75 mm for traffic category T4 and
by 100 mm for traffic categories T5 to T7. The reduction
in crust thickness is partly in the thickness of modified
soil with C.B.R. more than 10 % and partly in the
thickness of granular sub base (GSB).
Conclusions
Based on the limited experimental work done in the
laboratory, following conclusions are drawn:
1. On addition of 2 % polypropylene fibres with
aspect ratio of 40, the soaked C.B.R value can be
improved up to 75 % in comparison with the unreinforced
soil.
2. The crust thickness is reduced by 75 to 100 mm for
different ESAL applications.
References
1. Boominathan A. (1999), “Randomly Distributed
fibre Reinforced Sand”, Short term course on
Geosynthetics and reinforced soil structure,
I.I.T.Madras, India, pp. XVI 1 to XVI 10.
2. Meenal Gosavi, K.A.Patil, S.Mittal (2004) Swami
Saran “Improvement of Properties of Soil in
Subgrade by Using Synthetic Reinforcement”
Journal of Institution of Engineers (India), CV, Vol.
84, pp.257-262, February 2004
3. Ranjan Gopal and Charan H.D. (1998) “Randomly
Distributed fibre Reinforced Soil”, IE (I) Journal,
Vol.79, pp. 91-100 .
Table 5: Reduction in Crust Thickness with increase in CBR value
Sr. CBR 1 to 2 Lakhs 2 to 3 Lakhs 3 to 6 Lakhs 6 to 10 Lakhs
No. ESAL (T4 ) ESAL (T5 ) ESAL (T6) ESAL (T7)
1. 3.05 % 375 mm 425 mm 475 mm 525 mm
2. 5.35 % 300 mm 325 mm 375 mm 425 mm