Scrap tyres are being disposed every day in huge numbers all around the world. Due to its size and inability to compress it acquires large portions of dumping sites. According to 2017 US Scrap Tire Management Summary (USTMA 2018) 255.61 million of scrap tyres were generated in US in 2017. According to USTMA (2018) scrap tyres are used to derive fuel, production of ground rubber and civil engineering applications mainly. In 2017 only 39 million tyres were disposed to landfills in USA. Derivation of fuel and recycling of rubber to by-products take up more energy whereas utilization for civil engineering applications requires less energy for the end product, which is beneficial in the long run. According to CEA (2005), 2.1 million tyres per year were imported and produced in Sri Lanka and no methods of disposal are found.
In Sri Lanka waste tyre disposal is not being carried out properly which results in mosquito breeding grounds and inadequate space for tyre dumps. The tyre collects rainwater and maintains damp interior allowing the vermin to grow. Currently there is no proper practice to shred tyres before dumping which elevates the prevailing issue. There are few organizations where reuse and recycle of used tyre is done for industrial purposes, but many are dumped improperly. The use of scrap tyre in civil engineering applications is gaining popularity as a solution for lightweight fill in embankments and economical earth retaining structures. These reuse methods have given a value to the scrap tyre waste. The substitution of scrap tyres to rock fill will decrease the requirement of virgin material from the quarries and it will reduce the damages done to the environment at the extraction quarries. Hence this method will give a value to the scrap tyre while reducing the requirement on rock fill.
USAGE OF TYRES IN CIVIL ENGINEEERING APPLICATIONS
According to research data only 8% of scrap tyres are utilized for civil engineering applications in 2017. Shredded tyres and whole tyres both are used for civil engineering applications such as;
- Artificial reefs,
- Floating breakwaters,
- Land improvement,
- Erosion control,
- Noise barriers.
- Highway crash barriers
- Landfilling are done by whole scrap tyres, while road resurfacing and landfilling are done by shredded tyres.
There are many case studies done by researchers when it comes to erosion control with the use of scrap tyres. Protection of a channel slope and reinforcement of a highway shoulder using a cost beneficial method is emphasized to be elaborated. Using whole scrap tyres in developing a retaining wall is another popular technique used. A researcher (1997) had carried out a comprehensive research study on using scrap tyres for soil stabilization. Tyres were prepared and placed in four different placing methods and an analysis was comparing load and displacements.
USE OF SCRAP TYRES IN GABION CONSTRUCTION
Although few studies have been done highlighting the importance of lightweight fill for earth retaining structures and suitability of using scrap tyres for civil engineering solutions, using shredded scrap tyres as a gabion basket fill material is still not studied extensively. In this research acceptability of shredded tyres as an alternate material for rock fill was discussed.
SYSTEMATIC METHOD OF DETERMINING THE SHREDED TYRES AS AN ALTERNATIVE MATERIAL FOR ROCK FILL
Factors to be considered
- Factor of safety is considered as 1.5 for overturning and sliding
- The minimum unit weight taken for the research is 8.2kN/m3
- The expected porosity for the gabion unit was 0.3-0.4
- Size of tyre pieces was 50mm × 100mm
- Size of gabion box was 500mm *500 mm* 500 mm
- The density of rock pieces used is 2.86 g/cm3
- The density of used tyre pieces was found to be 1.15 g/cm3
PACKING ARRENGMENT OF SCRAP TYRES TO THE GABION BOX
LOAD TESTINGS DONE
A gabion basket of 50cm × 50cm × 50cm was prepared. Then rock pieces were arranged in the gabion basket where the largest dimension is in between 75mm to 100mm. An image analysis was done for the testing from two faces of the gabion unit in order to obtain a deflection pattern during application of loads. Two rulers were placed on sides of the gabion unit for this purpose as seen in the Figure 3. After the packing of the rock pieces apparatus was fixed for the loading and dial gauges were located around the gabion basket to obtain the readings of deflection.
A similar apparatus was positioned to test the gabion unit filled with rock and tyres. The largest dimension of rock pieces was in between 75mm to 100mm and the dimension of tyre pieces was 50mm × 100mm. The pieces were arranged in the 50 cm × 50 cm gabion basket. Dial gauges were placed on three faces in order to read the deformation along x, y and z planes
- According to the calculations it was found out that one gabion unit can reduce its unit weight up to 8.2kN/m3 for a given soil condition.
- For the obtained minimum unit weight, a porosity of 0.4 was obtained from using 100mm × 50mm tyre pieces and rock pieces where the highest dimension was in between 75mm – 100mm.
- The tyre included gabion unit could safely withstand 3 units of gabion units without excessive deformations.
- Direct cost of the new arrangement was not significantly lower compared with conventional arrangement, but in the large scale the cost reduction can be significant.
- However, due to usage of waste tyres, the threat to the environmental will be minimized and once it convert to the cost that will be greatly significant.
This research work is a collaborative work with University of Moratuwa (Dr. Udeni Nawagamuwa) and Access Engineering PLC (Dr. Praneeth Wickramarachchi). AEPLC has provided all gabion material requirement and industrial knowhow and costing details to carry out the work. In addition, technical and environmental details have been deeply shared during the research work.
Content submitted by Dr.Praneeth Wickramarachchi