Soil Reinforcement by Using Waste Fibers: A Review

Review Article

Soil Reinforcement by Using Waste Fibers: A Review Alok Sharma1

Abstract Lack of strength of any soil is due to poor condition of that soil which leads to deformability. Soil reinforcement is a technique to improve the engineering characteristic of soil thus increasing the strength of soil. Inclusion of Fibers in the soil for reinforcing it is one of the methods of soil reinforcement. Fibers are obtained from natural, synthetic and waste (nonhazardous type) Materials. Disposal of waste tire and waste plastic pose a major problem everywhere. These waste materials can be used as soil reinforcement. Keeping in view the environmental effects of waste materials literature review is undertaken on utilization of these materials in geotechnical applications.

Keywords:

CBR, Bearing capacity, Fiber reinforcement, Reinforced soil, Tire chips, Triaxial test, Waste plastic strip

Introduction In any civil engineering construction work, the structure should be safe against any type of failure and it should be economical. When the structure is constructed over weak or loose soil then it is difficult to fulfill these two conditions. Large amount of soil is used in the construction of roads and highways but sufficient amount of soil of required quality is not available easily So Stabilization of soil must be done before constructing any structure on it.

Soil stabilization may be broadly defined as the alteration or preservation of one or more soil properties to improve the engineering characteristics and performance of a soil, thus improving the load bearing capacity of a sub grade to support pavements and foundation .Soil can be stabilized in many ways and soil reinforcement is one of the methods of stabilization. Soil reinforcement is an effective and reliable technique for increasing the strength and stability of soils. The technique is employed today in several applications varying from retaining structures and embankments to sub grade stabilization, beneath footings and pavements. Reinforcement can vary greatly; either in form (strips, sheets, grids, bars, or fibers), texture (rougher smooth), and relative stiffness (high such as steel or low such as polymeric fabrics). Fibers are obtained from natural, synthetic and waste (nonhazardous type) materials, and therefore, they may be categorized into the following three types Natural fibers, Synthetic fibers, Waste fibers. Old/used tires and waste plastic materials are available in large quantities worldwide; they may be utilized in construction projects in various forms, especially in the granular form, chips or fibers; otherwise they might take up a large volume of the landfills when disposed of. With an average, an Indian uses 1 kg of plastic materials per year and the World annual average is about 18 kilogram.

It is estimated that about 4-5% post-consumer plastics waste materials by weight of Municipal Solid Waste (MSW) is generated in India somewhat more around 6-9% in USA, Europe and other developed countries. As per data available on MSW, approximately, 4000-5000 tonnes per day post-consumer plastic waste are generated.2 Disposal of the waste tires in sanitary landfills and stockpiling of tires is a major problem in every part of world.

1

Department of Civil Engineering, GNDEC, Ludhiana, Punjab, India.

E-mail Id: sharmaalok1023@yahoo.com Orcid Id: http://orcid.org/0000-0003-1987-3082 How to cite this article: Sharma A. Soil Reinforcement by Using Waste Fibers: A Review. J Adv Res Glass Leath Plast Tech 2017; 2(1&2): 5-11.

Š ADR Journals 2017. All Rights Reserved.

Sharma A

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

Each year a sizable part of industrial waste material is disposed of in landfills or promptly discharged to the environment. Therefore, researchers are looking for the alternatives so that waste material can be used in engineering applications. Rubber from worn vehicles tires and waste plastic from bottles after being shredded into smaller pieces can often be reused in geotechnical applications. Because of low density and high durability, shear strength and thermal insulation of tire chips, it can be use effectively in many geotechnical applications. Using tire chips as lightweight geomaterial for embankments or as backfill against retaining walls can be a good alternative because they are cheaper when compared with other conventional fill materials.22 Tire chips Waste Rubber and plastic is cut in small strips or in the form of fiber before using as reinforced material in soil. In construction works, fibers are generally mixed randomly with soil, resulting in randomly distributed fiber-reinforced soil (RDFRS), which is often simply called the fiber-reinforced soil (FRS).23

Waste Plastic Fiber The use of plastic waste in engineering applications reduces the problem of disposal of this nonbiodegradable waste causing environmental hazards.

Plastic waste in the form of strips has been used by different researchers to evaluate the performance of plastic waste in improving the properties of soil.

Plastic waste is easily available with rag pickers at very cheap price approximately INR 100Per kg.

Different dimensions of Plastic strips have been used in different studies to find out the optimum dimension and fiber content (percentage with respect to weight of soil) in soil which gives reliable results.

One of the major criteria for deciding the fiber dimension is aspect ratio. The ratio of length L to thickness (or equivalent diameter) D of the fiber is called the aspect ratio.21 Figure 1 is showing a type of plastic fiber taken from Babu SGL et al..6

Figure 1.Plastic Fiber

Effect of Waste Plastic Fiber on Soil Choudhary AK et al. studied to investigate the CBR behavior of waste plastic strip reinforced soil.2 In his study, a series of California Bearing Ratio (CBR) tests were carried out on randomly reinforced soil by varying percentage of HDPE strips with different lengths and proportions. Results of CBR tests demonstrated that inclusion of waste HDPE strips in

sand with appropriate amounts improved strength and deformation behavior of sub grade soils substantially. Keeping aspect ratio 3 and strip content 4% gives the best result on which increase in CBR and secant modulus was maximum. In this study it was found that maximum CBR value of reinforced sand was about 3 times that of unreinforced sand. Figure 2 shows Load penetration curve for varying strip content having AR = 3, which is the optimum value.

6

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

Sharma A

Figure 2.Load Penetration Curve for Varying Strip Content having AR = 3

The proposed technique can be used to advantage in embankment/road construction.

Babu SGL et al. examined to investigate strength and compressibility response of plastic waste mixed soil.6 Depending on experimental test results, it is observed that the effectiveness of soil is improved and compressibility reduced significantly with addition of a little percentage of plastic material waste to the soil.

Number of unconfined compression, consolidated undrained (UCC, CU) and one dimensional compression tests is performed with various percentages of plastic waste .The results shows that there is 73.8% increase in unconfined strength, 37.2% reduction in compression index for 1% plastic waste mixed red soil and 93.7% increase in unconfined strength, 26.6% reduction in compression index for 1% plastic waste mixed sand compared to plain soil.

Similar positive results are obtained in consolidated undrained test on red soil and sand at different confining pressures. Increase in strength of soil is due to increase in friction between soil and plastic waste and development of tensile stress in the plastic waste.

Also reduction in compression parameters of plastic waste mixed when compression behavior was studied.

Consoli et al. carried out unconfined compression and drained triaxial tests on uncemented and cemented sands, reinforced with plastic fiber (polyethylene terephthalate) that is obtained from recycled PET plastic waste. In this study they found that the unconfined compressive strength and the tensile strength of the cemented sand (cement content of 5%) were increased by 40 and 70% respectively with the inclusion of fiber reinforcement. PET fiberreinforced cemented sand in triaxial compression

7

shows effective increase in peak strength, due primarily to an increase in the friction angle from 43 to 49°.Results of this article shows the dependence of efficiency of fiber reinforcement on fiber length. The improvements in triaxial strength, ductility, and energy absorption capacity were observed for the 36 mm plastic fiber.

Dutta RK et al. investigated the CBR behaviour of waste plastic strip reinforced stone dust/fly ash overlying saturated clay.5 By using Different sizes and length of waste plastic strips content (0.25% to 4%) on the CBR and secant modulus of strip reinforced-stone dust/fly ash overlying saturated clay was investigated.

With the increase in fiber content and length, improvement in CBR or secant modulus value had been seen up to 2% of fiber content. Also reinforced stone dust is more effective than reinforced fly ash overlying saturated clay in improving the behaviour of the system. This material can be effectively used in base courses in constructing rural roads over saturated clay, which helps to safe disposal of waste material in environmental friendly manner.

Laskar A et al. investigated to evaluate the effect of plastic fiber on compaction and consolidation behaviors of reinforced soil.4 HDPE waste plastic bottle fibers of different aspect ratios (2, 4 and 8) with different fiber percentages up to 1% had been used in sandy-silt soil with clay. Test results of standard proctor test indicated that maximum dry density (MDD) of plastic reinforced soil decreases with increasing fiber content but optimum moisture content (OMC) shows no increment or decrement because fiber does not absorb water. Values of compression index (Cc) and coefficient of volume

Sharma A

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

change (mv) of soil decreases up to 0.50% fiber content but then increases with further addition of plastic fiber of 1% in soil. Coefficient of consolidation increases with the increase of plastic fibers in soil for aspect ratios 2, 4 and 8. These waste plastic fiber reinforced soil of present study encouraging for potential use in the field of geotechnical engineering construction by enhancing the strength and reducing the settlement.

Waste Tire Fiber Rubber does not decompose and as a result, an economically feasible and environmentally sound

disposal method has to be found out. Tire chips and tire shreds are nonreactive under normal environmental conditions. Synthetic rubber is the main chemical component of tires. Huge amount of used tires discarded every year can be effectively used in geotechnical and geoenvironmental applications. A lot of research has been done on the usage of shredded rubber tires in pavement engineering, to stabilize the sub grade of the pavements. Typical shapes of different processed used tires are mainly of four types which are used as soil reinforcement i.e. tire shreds, tire chips, tire buffing, tire crumb.21 Figure 3 of shredded tire rubber has taken from Tafreshi et al.12

Figure 3.Shredded Tire Rubber

Effect of Waste Plastic Fiber on Soil Moghaddas Tafreshi SN et al. carried out number of laboratory tests were carried out on square footings supported on the rubber reinforced and unreinforced soil beds.12 This study showed the comparison between bearing pressure of footing of reinforced soil with rubber shreds and soil cap with unreinforced sand. Shredded tire rubbers (aspect ratio between 3 and 5) were mixed in the soil and that rubber reinforced soil was sandwiched between two

unreinforced soil layers. The optimum value of rubber content was found 5 % where bearing capacity was increased significantly and keeping same rubber content the optimal thickness of rubber reinforced soil was 0.5 times the width of footing and soil cap (layer of sand above rubber reinforced soil) was 0.25 times the width of footing. Also, with inclusion of 5% rubber content, at the settlement level of 5%, bearing capacity of rubber reinforced bed was around 2.68 times of the unreinforced bed.

8

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

Sharma A

Figure 4.Variation of Bearing Pressure with Footing Settlement for Unreinforced and Rubber-Reinforced Soil with Different Values of Thickness of Reinforcement Layer, for Rubber Content 5% and Thickness of Soil Cap is 0.25

So usage of shredded waste tires as a reinforcement material in soil gives satisfactory results. Hataf N. et al. conducted to study the use of shredded waste tires as reinforcement in soil to increase the bearing capacity of soil. Load bearing capacity of circular footing on tire shred reinforced sand and unreinforced sand was calculated by plotting different load settlement curves. Tire shreds of rectangular shape having width of 2 cm and 3 cm have been used.

Tire shred content was kept between 10% to 50% (by volume) and aspect ratio was kept between 2 to 5. It was reported that by adding the 40% shred content of aspect ratio 4 there would be maximum increment in BCR (bearing capacity ratio) from 1.17 to 3.9. It has been also observed that further increment in shred content from 40% would not increase the BCR value significantly.

Rao GV et al. investigated to understand the compressibility and triaxial behavior of sand –tire mixtures.9 For investigating the behavior of sand with and without inclusion of tire chips compressibility tests, repeated load tests and triaxial tests were performed. Tire chips of varying percentage and size were used under different test conditions. Mainly 10mm and 20 mm sized tire chips were used. When sand-tire chip mixtures were compacted in a rigid mould (CBR mould) it was found that vertical strain increases with vertical stress applied, for all chip contents up to 20 % chip content only. In case of triaxial tests it was shown that both initial tangent modulus and the secant modulus decreases with an increase in chip content and effective angle of

9

shearing resistance increased by 2o with 20% tire chip content in sand. With same tire chip content some improvement in strength have also be shown in results using the tire chip of aspect ratio 2. So in this study they concluded that tire chips can be use in construction of highway embankments up to 10m height replacing conventional fill material.

Singh B et al. examined to investigate the effect of waste tire chips on the strength characteristics of cohesive clayey silt soil and cohesion less fine sand soil.14 For evaluating the performance of tire mixture in cohesive soils, Standard Proctor tests, unconfined compression tests and California bearing ratio tests was carried out by mixing 5 to 20% tire chips content by weight. Vibratory compaction tests and direct shear tests were performed on the cohesion less soiltire mixtures by adding tire chips 10% to 50% by weight. For the cohesive soil, irregular and elongated tire chips of maximum dimension less than 7 mm were used and rectangular sizes tire chips of 10 mm, were used for cohesion less soil. It was reported that the addition of 13% tire chips content for cohesive soil and 30% for the cohesion less soil, was optimum at which behavior of both the soils in different test had been improved significantly.

Naval S et al. conducted to study triaxial tests behaviour on waste tire rubber fiber mixed granular soil.15 To investigate the improvement in shear strength parameter of sand, Drained triaxial tests (CD) were carried out with the inclusion of rubber fiber under different cell pressures. Fiber content of length 1.5-2 mm and the triaxial tests were performed at

Sharma A

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

different relative densities of soil. It was seen in this study that shear strength properties were improved at all the fiber contents up to 0.75% at all the cell pressures but the maximum improvement in shear strength was at 60% Relative density (RD). In rubber fiber reinforced soil peak stress values and the corresponding strains were improved and observed post peak losses were less when compared with unreinforced soil.

Conclusions All the concerned article has usually explained that material property is found to be improved by inclusion of fiber.CBR values of soil increased effectively by maintaining the optimum aspect ratio of plastic fiber.

Unconfined compressive strength and stress strain behavior of soil have improved with inclusion of waste plastic fiber up to certain fiber content. Bearing capacity of soil has also improved when the soil is reinforced with shredded tire waste. Strength improvement of soil increased up to particular tire chip fiber content percentage. So it is feasible to use these waste materials to enhance the engineering properties of soil and also decrease the requirement of valuable land for their disposal .Tire waste and plastic waste can effectively use as soil reinforcement beneath footing, embankment and retaining wall this concept is environmental friendly and reduce the disposal problem. Summary of the literature is given in Table 1.

Table 1.Comparison of Distinct Type of and their Characteristics

S. No 1

Authors Choudhary AK. et al.2

Fiber type and percentage High density polyethylene strips (0.25% to 4%) Plastic waste chips (0.5%, 0.75%, and 1%)

2

Babu SGL et al.6

3

Consoli NC et al.1

Polyethylene Terephthalate fiber (0.1% to 0.9%)

4

Dutta RK et al.5 Laskar A et al.4

Waste plastic trip (0.25% to 4%) Waste plastic trip (0.25%, 0.5%, and 1%)

6

Tafreshi SN et al.12

Shredded tire rubber (2.5%, 5%, and 7.5%)

7

Hataf N et al.13

Shredded tire rubber (10% to 25%)

8

Rao GV et al.9

9

Singh B et al.14

Shredded tire rubber (5% to 20%) Tire chips (5% to 20%) and (10% to 50%)

10

Naval S et al.19

Rubber tire fiber (0.25% to 1%)

5

Conclusions a. b.

CBR value and secant modulus of sand increased.

Optimum value of strip content is 4% and aspect ratio is 3.

a.

Triaxial compression test (UCC and CU) showed increase in strength of soil with inclusion of plastic. b. One dimensional compression test showed decrement in compression parameters of soil. a. Unconfined compressive strength and the tensile strength of the cemented sand (cement content of 5%) were increased. b. Increase in friction angle and peak strength in triaxial compression.

Increase in the CBR and the secant modulus of stone dust/fly ash overlying saturated clay sub grade with 2% fiber content. a. MDD (maximum dry density of plastic reinforced soil decrease with fiber inclusion in soil b. Coefficient of consolidation increases with fiber inclusion in soil Addition of 5% rubber content at the settlement level of 5%, led to increase in bearing capacity of rubber reinforced bed around 2.68 times of the unreinforced bed.

BCR (bearing capacity ratio) of sand increased From 1.17 to 3.9 by addition of 40% shred tire content of aspect ratio 4.

A Sand-tire chip mixture shows improvement in results of compressibility and triaxial compression with 20% fiber content. a. Unconfined compressive strength and CBR value increase by addition of 13% tire chips in Cohesive soil b. Optimum value of cohesion less soil was 30% tire chip content which enhances the strength of soil.

Friction angle and post peak behaviour of triaxial test was improved by inclusion of 0.75% fiber content

10

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

References 1. Consoli NC, Montardo JP, Prietto PDM, et al.

Engineering behavior of sand reinforced with plastic waste. Journal of Geotechnical and Geoenvironmental Engineering 2002; 128(6): 462-72.

2. Choudhary AK, Jha JN, Gill KS. A study on CBR behavior of waste plastic strip reinforced soil.

Emirates Journal for Engineering Research 2010.

3. Moghaddas SN, Norouzi AH. Bearing capacity of a square model footing on sand reinforced with shredded tyre - an experimental investigation.

Construction and Building Material 2012; 35: 54756.

4. Laskar A, Pal SK. Effect of waste plastic fibres on compaction and consolidation behaviour of reinforced soil. Electronic Journal of Geotechnical Engineering 2013; 18: 1547-58.

5. Dutta RK, Sarda VK. CBR behaviour of waste plastic strip-reinforced stone dust/fly ash overlying saturated clay. Turkish Journal of Engineering and Environmental Sciences 2007; 31: 171-82.

6. Babu SGL, Chouksey SK. Stress-strain response of plastic waste mixed soil. Waste Management Journal 2011; 31: 481-8.

7. Mishra P, Satrawala M, Amin H. Experimental study on Waste Recycled Product (W.R.P) and Waste Plastic Strips (W.P.S) as pavement sub base material. International Journal of Scientific and Technology Research 2013; 2(12).

8. Bhattarai P, Kumar B, Santosh K, et al. Engineering behavior of soil reinforced with plastic strips.

International Journal of Civil, Structural, Environmental and Infrastructure Engineering Research and Development 2013; 3(2): 83-8.

9. Rao GV, Dutta RK. Ground improvement with plastic waste. International Conference on Ground Improvement Techniques, Malaysia.

2004. pp. 321-328 10. Chebet FC, Kalumba D. Laboratory Investigation on re-using polyethylene (plastic) bag waste material for soil reinforcement in geotechnical engineering. Civil Engineering and Urban Planning: An International Journal 2014; 1(1).

11. Venkatappa Rao G, Dutta RK. Compressibility and strength behaviour of sand-tyre chip mixtures.

Geotechnical and Geological Engineering 2006;

11

Sharma A

24(3): 711-24.

12. Moghaddas Tafreshi SN, Norouzi AH. Bearing capacity of a square model footing on sand reinforced with shredded tyre - an experimental investigation. Construction and Building Material 2012; 35: 547-56.

13. Hataf N, Rahimi MM. Experimental investigation of bearing capacity of sand reinforced with randomly distributed tire shreds. Construction and Building Materials 2006; 20: 910-6.

14. Singh B, Vinot V. Influence of waste tyre chips on strength characteristics of soils. Journal of Civil Engineering and Architecture 2011; 5(9): 119-27.

15. Naval S, Kumar A, Bansal SK. Triaxial tests on waste tire rubber fiber mixed granular soil.

Electronic Journal of Geotechnical Engineering 2013; 18: 1623-41.

16. Tanchaisawat T, Bergudo DT, Voottipruex P, et al.

Interaction between geogrid reinforcement and tyre chip-sand lightweight backfill. Geotextiles and Geomembranes 2010; 2: 119-27.

17. Akbulut S, Arasan S, Kalkan E. Modification of clayey soils using scrap tire rubber and synthetic fibers. Applied Clay Science 2007; 38: 23-32.

18. Yoona YW, Cheonb SH, Kang DS. Bearing capacity and settlement of tire-reinforced sands.

Geotextiles and Geomembranes 2004; 22: 439-53.

19. Naval S, Kumar A, Bansal SK. Pressure settlement characteristics for Strip footing resting on sand reinforced with waste tyre fibers. Electronic Journal of Geotechnical Engineering 2012; 117: 3771-95.

20. Zornberg JG, Cabral AR, Viratjandr C. Behaviour of tire shred - sand mixtures. Canadian Geotechnical Journal 2004; 41(2): 227-41.

21. Edinรงliler A, Baykal G, Saygili A. Influence of different processing techniques on the mechanical properties of used tires in embankment construction. Waste Management 2010; 30: 1073-80.

22. Oikonomou N, Mavridou S. The use of waste tire rubber in civil engineering works. Sustainability of Construction Materials, Woodhead Publishing, Cambridge. 2009. pp. 213-238 23. Shukla SK. Fundamentals of fiber-reinforced soil engineering. Developments in Geotechnical Engineering, Springer Nature Singapore Pte Ltd. 2017.