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International Travel Grant Scheme, Royal Academy of Engineering

Report on a Technical Visit to the United States of America: May 2004

Dr M G Winter Regional Manager TRL Limited, Redwood House, 66 Spylaw Road, Edinburgh, EH10 5BR, UK INTRODUCTION In May 2004 I visited the United States of America to discuss the application of tyre bales to construction projects with key individuals in New York State and Texas. Tyre baling is a new process and the bales have the potential for widespread use in construction. The main purposes of my visit were to capture the experiences of those who have been involved in the use of tyre bales over the last 5 to 6 years (since the process was first marketed). This was to allow those experiences to be brought to bear on emerging UK practice, while also passing our experiences on to our colleagues in the USA. Waste management remains a particular barrier to the use of tyre bales at present and I also hope to acquire experience the approach taken to waste management licensing in the USA and how this and other barriers to recycling have been addressed for tyres and other materials. In my role as Assistant Editor (Geomaterials) of the Quarterly Journal of Engineering Geology and Hydrogeology (QJEGH) I also canvassed for paper submissions from those that I met. BACKGROUND Around 38.7M tyres (or 440,000t) were scrapped in the UK in 1998 (Hird et al., 2001). In Scotland more recent, and accurate, data is available corresponding to 2.8M tyres (or 32,000t) in 1999 (SEPA, 2002). In the recent past by far the bulk of these have been sent for energy recovery, stockpiled, disposed of in landfill or disposed of illegally (Hird et al., 2001). However, the EC Landfill Directive outlawed the disposal of whole tyres in landfill from June 2003 and will outlaw the disposal of shredded tyres to landfill by 2006. A useful review of the status of post-consumer tyres in the EU is provided by Shulman (2002). Clearly alternative means of disposal are required. It is expected that a significant proportion of the UK's used tyre production and existing stock will be consumed by waste-to-energy plant (including burning in cement kilns) for example. However, such activities will not account for all used tyres and a significant proportion is expected to remain available for alternative uses.

Potential recovery options for waste tyres include retreading, material recovery (mainly crumbing) for use in new rubber products, energy recovery (including pyrolysis) and use in civil engineering. Civil engineering applications take on many forms including ranging from landfill engineering; through lightweight fill, soil reinforcement, drainage, erosion control, artificial reefs, hydrocarbon retardation in ground barriers and noise barriers; to thermal insulation (Hylands and Shulman, 2003). The form in which the tyre material may be used varies from small crumb and shred particles up to whole tyres depending upon the application and the technical requirements thereof. The fabrication of tyre bales, although mentioned by Hylands and Shulman (2003), is a relatively new means of tyre recovery. Tyre baling involves the use of a specialist machine to produce a highly compressed block containing in excess of 100 car or van tyres for use in construction. The dimensions of the block are approximately 1.50m by 1.27m by 0.77m and the blocks have a density of around 0.7Mg/m3 or less, representing a volume reduction compared to the loose tyres of around four or five to one. The blocks are usually tied by galvanised steel wires (mesh and polymeric materials can also be used depending upon the installation environment) and when completed are sufficiently regular that they may be stacked. Importantly the baling machine is trailer mounted and may be relatively easily transported to large volumes of tyres. ROAD CONSTRUCTION OVER SOFT GROUND, CHAUTAUQUA COUNTY, NEW YORK STATE, USA I met with Ken Smith, Director of Roads for Chautauqua County, and the Mark Thomas the County Legislator. The Chautauqua Count Department of Public Facilities have led a total of five projects involving the use of lightweight tyre bales as a subgrade replacement for roads over soft ground. The tyre bales resulting from the clean up of the Levant tyre dump and from the ongoing tyre amnesty programme were used in these projects. A further project is planned for 2005 and it is anticipated that future projects of this nature will depend upon the availability of tyres for baling. The geology of the County is characterised by sands and gravels in the river valleys with glacially deposited fine silty clays elsewhere, primarily on the hilltops which are often depressed forming high level swamps. These latter materials are generally stable if kept dry but are very sensitive to moisture and even more so to the freeze thaw cycle which can turn them to a material not dissimilar to pottery slip and are capable of turning conventional roads constructed over them into impassable quagmires. It is on these relatively high level roads that the County Authorities have targeted tyre bale road construction. To date all of the tyre bale roads have performed satisfactorily, the first having been completed in Summer 1999. Figures 1 and 2 show the construction and present condition of The Kabob Road (County Road 342 / Touring Route 71) which was completed in Summer 2000.

My visit coincided with the launch of the Fifth Annual Chautauqua County Tyre Bale Amnesty. The County facilitates the free collection of waste tyres at pre-defined collection points. Over the five years the programme has achieved significant reductions in illegal dumping of tyres and, indeed, the size of legal dumps. Tyres can act as a breeding ground for West Nile Fever carrying mosquitoes, a disease from which five people have died in recent years in New York State alone. The tyres collected in the amnesties have been used in the manufacture of the blocks which have, in turn, been used in the construction of the tyre bale roads.

Figure 1 ­ Construction of the tyre bale Appendix of CR342 ­ placement of the sand layer. (Photograph © Chautauqua County Department of Public Facilities.)

Figure 2 ­ CR342 in May 2004. The other major concern in the USA is fires at tyre dumps. Indeed, it was a fire at the town of Charlotte in Chautauqua County in April 1995 that led to the tyre amnesty. The fire burned for weeks, costing the local economy hundreds of thousands of US

dollars and bankrupted several local fire departments (Anon, 1998; 2001). The fire destroyed an estimated 20% to 25% of the 5M tyres stored at the dump (Figures 3 to 4).

Figure 3 ­ Tyre dump fire at Hornburg dump, Charlotte , New York State. (Photograph © Chautauqua County Department of Public Facilities.)

Figure 4 ­ Tyre dump fire at Hornburg dump, Charlotte, New York State. (Photograph © Chautauqua County Department of Public Facilities.) Excellent information was gathered on the design and construction of tyre bale roads during my visit to Chautauqua County and it is hoped to develop a joint paper on this subject. Additionally information on tyre fires was collected which has provided useful background material.

SLOPE FAILURE REPAIR, INTERSTATE HIGHWAY 30, TARRANT COUNTY, TEXAS I met with Richard Williammee, Fort Worth District Engineer for the Texas Department of Transportation while in Texas. The remediation of soil cut slope instability in Tarrant County, Texas has conventionally been achieved using existing or imported soils, with or without modification by hydraulic binders and often in conjunction with an `H'-beam wall, in order to minimise costs and construction time. More recently consideration has been given to the use of tyre bales as a partial replacement for soil fill. This approach has been observed to provide a significant improvement to the subsequent long term stability of the repair while also providing for the beneficial reuse of waste tyres. This is especially significant where the in-situ soils comprise high plasticity clays, which may be marginal for such applications, highly moisture sensitive and inherently unstable. Surface or groundwater seepage also may be a contributing factor to slope instability. Interstate Highway 30 runs between Dallas and Fort Worth and in the first half of 2002 a portion of the cut slope adjacent to the east bound lanes of IH30 west of Oakland Boulevard failed. The length of the failed slope was approximately 150' (46m), the slope height reached 20' (6.1m) at a constant 1 in 3 (V:H). The failed area was subsequently repaired by first removing the failed material as shown in Figure 5. (The pilot holes for an `H'-beam wall can be seen in the base of the excavation. This was initially planned to be constructed but was abandoned in favour of the tyre bale option.) The excavation was taken back up to 35' (10.7m) from the original toe of the slope.

Figure 5 ­ The IH30 slope failure after excavation of the failed material. (Photograph © Texas Department of Transportation.)

It is important to note that the works were carried out rapidly with a minimum of design input. Such an approach is frequently described in the UK as Emergency Works. The slope was repaired using tyre bales as a backfill material (Figure 6). However, the supply of tyre bales unexpectedly dried up during construction and only three of a possible six layers were placed.

Figure 6 ­ Placing tyre bale layer one in the excavated IH30 slope failure. (Photograph © Texas Department of Transportation.) This has led to an interesting situation that demonstrates the potential effectiveness of tyre bales in slope repair. My site visit was on the morning after a thunderstorm and water could be heard percolating through the tyre bales and seen emerging from the base of the slope (Figure 7). Additionally, the upper part of the slope which was repaired using in-situ soil materials is showing considerable signs of distress (Figure 8) and is likely to need further repair work and it is proposed that tyre bales be used for this purpose. A post-failure and repair investigation of the slope was carried out by TEAM Consultants for the Texas DoT. Contact has been made with Bill Prikryl of TEAM and a joint (Prikryl, Williammee and Winter) paper on the slope repair and subsequent analysis is about to be submitted to the Quarterly Journal of Engineering Geology and Hydrogeology. The Texas DoT were kind enough to pass on a great deal of information regarding tyre bale properties and fire risk. Contact has since been made with the Texas Tech University at Lubbock and the University of Texas at Austin and this has led to a fruitful and mutually beneficial exchange of information. This included further information on fire risk and this combined with information from New York State and elsewhere has allowed the risk of spontaneous combustion of tyre bales to be better evaluated, as effectively negligible.

Figure 7 ­ Water drained to the front face of the slope by layers one and two of the tyre bales, May 2004.

Figure 8 ­ Cracks at the crest of the slope in May 2004, demonstrating potential for further failure in the upper part of the slope which was backfilled with insitu soil rather than tyre bales.

CONCLUSIONS My trip to the USA was extremely useful and I managed to assimilate even more information on tyre bale use in construction than I had hoped. Not all aspects of the trip went well. I had hoped to meet with either Ed or Nancy Drews of Encore Systems Inc, the manufacturers of the tyre baling machines. They had planned to travel form their base in Grand Rapids in Minnesota to meet with me in Texas. Sadly a family crisis meant that they were unable to travel. However, we did manage to have several very fruitful telephone conversations both during and since my visit and I do not think missing out this part of my visit reduced the value that came form it. Indeed, it enabled me to spend more time with Texas DoT and probably increased the amount of information that was acquired. Contact with those I met, and others, have continued since my visit furthering the fruitful exchange of information that occurred in May. One paper has been submitted on the Texas Slope Failure Repair; others are planned. In addition to funding form the Royal Academy of Engineering, funding for this visit was also received from the Onyx Environmental Trust. R EFERENCES Hird, A B, P J Griffiths and R A Smith (2001). Tyre waste and resource management: a mass balance approach. Viridis Report VR2. Crowthorne: TRL Limited. Hylands, K N and V Shulman (2003). Civil engineering applications of tyres. Viridis Report VR5. Crowthorne: TRL Limited. SEPA (2002). Waste data digest 2002. Stirling: Scottish Environment Protection Agency. Shulman, V L (2002). The status of post-consumer tyres in the European Union. Report VR3. Crowthorne: TRL Limited.


Report on a Technical Visit to the Czech Republic: August/September 2003

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