Reported problems with early compactors were a tendency for the wheels to pick up refuse, particularly in wet weather, and instability due to a high centre of gravity.

The steel wheels are fitted with spikes, lugs or bars for compression and traction purposes and the configuration of the track and wheel spikes is very important. The reported fault depends to some extent on these features but it has been found that tipping in more shallow layers often overcomes this difficulty.

Modern landfill compactors would be expected to have a life expectancy and maintenance profile not far removed from other landfill plant, just don’t expect performance equivalent to civil engineering earthworks uses.

Scrapers, both towed and independently powered, are seldom seen on landfills after initial development of the bases of landfills. They are used to strip, store and replace top and subsoil, and various forms of civil engineering earthworks equipment will clearly be used for such work including mechanical diggers and trenching equipment are used on site works.

Certain features are essential when buying either vehicle;

(i) they should have cabs with roll-bars for the protection and comfort of the operator;

(ii) if a bulldozer is purchased, the blade should be designed for handling refuse — it should be higher and wider, and should stand off from the vehicle further than is normal;

(iii) a wheeled vehicle should be equipped with four-wheeled drive;

(iv) the fan should blow out from the engine instead of drawing air in, in order to reduce the risk of choking the radiator with refuse;

(v) the wheels or drums of a compactor should be self cleaning and suitable to deal with the material being imported.

The choice of landfill mobile plant depends on a number of factors; quantities and types of wastes; the activities required of the machinery; whether the material delivered to the site has been previously treated; location and nature of any materials on site which might be used for side or top cover. However, wheeled vehicles will always be popular.

Cost Considerations

When purchasing a vehicle for controlled tip work, running costs must inevitably be considered along with the standard of work which the vehicle is capable of achieving. In the case of a tracked vehicle, track maintenance costs can be high as there is a great deal of wear due to the abrasive nature of the material in which the tracks are running, but costs can be reduced by changing the vehicle before major repairs are necessary and when the exchange value is favourable.

The disadvantage of punctures has to some extent been overcome as far as wheeled vehicles are concerned, and is completely eradicated for steel-cutting wheel equipped compactors, but taking into consideration their quality of work, whilst they may be faster they are not capable of the high standards of levelling of the tracked vehicle.

Tyre bales at Pevensey

It will be obvious to our Wastersblog readers that the disposal of vehicle tyres is a real headache, for the waste management industry, and as motorists we are all feeling the pinch from rapidly rising tyre disposal costs.

Certainly, the last time I bought a new tyre, the garage added several pounds to my bill for disposing of the old one.

However, a number of landfill operators have been using tyres for leachate drainage within landfills for some years as an engineering material, and they have found that using tyres as drainage layers in landfills provides adequate flow capabilities, at close to zero cost for their leachate drainage. However, manhandling individual tyres to stack them efficiently on site is a tedious, dirty, and time consuming task, and this fact alone has probably done a great deal to limit tyre use uptake. Whole and granulated tyres have been used for this purpose.

That was for whole tyres, as far as we are aware, just about the only use available in landfills.

Since WRAP published a British Standards Institution (BSI) and has produced a Publicly Available Specification, PAS 108, in collaboration with the tyres reprocessing industry, a whole new range of uses has opened up, from baled tyres.

Almost overnight, baled tyres have become an engineering product with standard bale sizes and shapes, and most important of all, clear design strength data.

Designers and purchasers can now use the structural and drainage characteristics provided from the research done for the PAS, and incorporate tyre bales into designs, just like any other proprietary geo-synthetic material.

In short, providing a specification for producing compact tyre bales of a consistent and verifiable quality and dimension, opens up a new and potentially huge market for waste tyres.

The method re-uses tyres, reducing the demand for the primary aggregate materials used in the past.

The PAS 108 specification can be adopted by suppliers for producing tyre bales such that potential customers will be assured that they are procuring a construction material of consistent and verifiable quality.

Furthermore, the core of this document addresses the production, handling, storage, transport and placement of standardized tyre bales, the dimensions and properties of which are standardised and described in this PAS. So go find out more at the Landfill Site Tyre Bales page here, and you will also find the contact details for one of the first suppliers.