A.K.Choudhary 1 , J.N.Jha 2 , K.S.Gill 3 1 Deptt. of Civil Engg., NIT, Jamshedpur, India 2,3 Deptt. of Civil Engg., GNDEC, Ludhiana, India PRESENTED BY: K.S.GILL [email_address]
Thickness of flexible pavement depends upon subgrade strength and traffic intensity.
Soil reinforcement is an effective and reliable technique to improve the strength of soil subgrade.
Geotextiles and geogrids are commonly used in engineering practices.
Waste plastic can be a cheaper alternative of costly georids/geotextiles for construction of low cost roads.
Solid waste production in India: 39 million tons /year (2000)
Expected production by 2010: 56 million tons /year
Typical %age of plastic in Municipal solid waste : 1% (India)
Best way to handle such waste :Utilization in engineering application
Application in Soil reinforcement : If found effective can be a significant secondary market for waste plastic
Possibility of replacing costly reinforcing material like geogrid
Effect of mixing different %age of high density poly ethelene (HDPE) strips on CBR value of subgrade soil .
Environment friendly disposal of non-biodegradable municipal waste.
To contribute towards the sustainable development of road infrastructure.
To reduce the construction cost.
SAND: Locally available sand(Jamshedpur,Jharkhand) (India)
Specific gravity: 2.62,
D 50 : 0.55 mm,
C u : 2.40, C c : 1.67
γ max : 16.5kN/m 3
γ min : 14.6kN/m 3
Purchased from a rag picker, at a price of INR 100 per kg (approximately $2per kg).
Width of HDPE : 12mm and Thickness: 0.40mm.
Length of HDPE : 12mm [Aspect Ratio (AR=length/width) =1],
(Selected) 24mm (AR=2)
Ratio of mould diameter to maximum strip length ≥ 4
(Ensures sufficient space for strip to deform freely and remains independent of mould confinement)
Ultimate tensile strength of this strip: 0.36kN
and percent elongation at failure: 23% (ASTM D 4885)
Strip content (Defined in present case): Ratio of weight of strips to the weight of dry sand.
Strip content selected for the tests: 0.0%, 0.25%, 0.50%, 1.0%, 2.0% and 4.0%.
Preparation of specimens:
CBR mould of 150 mm diameter and 175 mm high
Density and relative density of compacted sand: 16.2kN/m 3 D r = 85%
No. of layers: Three
Density of HDPE strip reinforced sand layers kept equal to dry density of that of unreinforced sand.
Required amount of HDPE strips were randomly mixed with dry sand.
Mix transferred to the mould and a surcharge (base plate 148 mm in diameter) weighing 25 N placed over the sample (to avoid segregation of the strips during vibration).
Compaction of specimen: vibration for 2 minutes on a vibration table.
Tests performed: As per procedures described in IS-2720-Part XVI-1987
A surcharge plate of 2.44kPa placed on the specimen prior to testing.
Loads recorded as a function of penetration (up to a total penetration of 12.5 mm).
CBR and Secant modulus determined from Load vs Penetration curve
CBR values reported in the present investigation are those of 5.0 mm penetration (CBR value at 5.0 mm penetration observed higher than that of 2.5 mm penetration even on repetition).
Increase in CBR value due to the presence of HDPE strip content: Expressed by California Bearing ratio Index (CBRI)
CBRI = CBR r /CBR u
CBR r : California bearing ratio (CBR) value of reinforced soil
CBR r : California bearing ratio (CBR) value of unreinforced soil
Secant modulus: Defined as the ratio of load in kPa at a penetration of 5.0 mm to the penetration of 0.005m
(obtained from load penetration curve)
Variation of load-penetration curves (AR=1) with different strip content (0.025% to 4.0%)
Variation of load-penetration curves (AR=2) with different strip content (0.025% to 4.0%)
Variation of load-penetration curves (AR=3) with different strip content (0.025% to 4.0%)
After completion of each test: Specimens were dissected and strip examined
Many of the strips showed elongation, thinning and clear impression of sand particles
As soil sheared during penetration, strip fixed in the sand by friction elongated as the soil deformed
CBR value of HDPE strip reinforced sand at 5.0mm penetration were found to be higher than those at 2.5 mm penetration
At higher deformation HDPE strip reinforcement is more effective in improving the strength of sand by increasing the resistance to penetration
Situation (a) plunger pushes down particle ‘C’ to occupy position in between particle ‘A’ and ‘B’
The strips resist the downward movement of particle ‘C’ until slippage between soil and strip occur resulting into a development of situation (b)
Interaction between soil and strips causes the resistance to penetration of the plunger resulting into higher CBR values
The addition of reclaimed HDPE strips a waste material to local sand resulted in an appreciable increase in the CBR and the secant modulus
The reinforcement benefit increases with an increase in strip content and the aspect ratio and maximum improvement in CBR and secant modulus of a reinforced system is around three times to that of an unreinforced system.
Though the maximum improvement in CBR and secant modulus is obtained when the strip content is 4% and the aspect ratio 3, but even at 2% strip content the improvement in CBR is also appreciable.
Small size of CBR mould limits size & amount of fibre inclusion
End effects in small sample size is more pronounced
Despite these limitations large experience base and satisfactory design method are in use based on CBR test results
Further study needed (a) to optimise the size, shape of strips