Plane solution offers crushing benefit for Lafarge

Lafarge Aggregates's dolemitic limestone quarry at Whitwell in Nottinghamshire, produces 1.5 million tonnes a year. Its main purpose is the supply of limestone containing very pure silica and iron to feed rotary kilns used in the production of materials for steel manufacture, while the lower benches of the quarry produce good clean limestone for the civil engineering market.

An extension area to the quarry provides a further ten year supply, unfortunately a main road came between these two areas. So that heavy duty vehicles could access and avoid the main road, Lafarge needed to dig an underpass.

This posed the challenge of ripping out rock for a new haul road as part of a huge project that would include closing a main highway passing through the quarry and building a new bridge to allow the haul road to proceed beneath. Once completed however, he project would allow the new area of the quarry to be opened on the opposite side of the existing quarry without having to use the main highway.

While the main road was temporary closed, a central section was pre-blasted to allow the construction of a concrete bridge deck. However the resulting ramp was almost a shear face blocking access to the extension with no way to get at this area without further blasting. This, of course, was out of the question because of the bridge's proximity.

A road planer was tried but it proved to be too slow and simply not up to the arduous conditions. Then Lafage found a solution offered by trenching contractor AJ Gammond in the form of a piece of equipment called the Rock Hawg.

Distributed in the UK and worldwide by Westquay Trading, The Rock Hawg rock excavator is designed and built by trenching technology engineering company Tesmec for trench excavation in reinforced concrete or solid rock. The machine will trench, excavate and crush in a single process, providing readily available, usable crushed materials for recycling or backfill - large or small, coarse or fine.

An alternative to blasting the Rock Hawk will not fracture the underlying rock bed, a typical problem when blasting. When heavy duty vehicles use haulage roads with a fractured rock bed pot holes or road break up will soon develop.

The Rock Hawg consists of a large main tractor unit with an attachment to the rear of the machine. Built with a trench width capacity of up to 3810 mm the Rock Hawg can trench working areas in a series of passes. Maximum trench depth is 600 mm and the drum can perform at speeds of 21, 30 or 39 rpm. The tractor is a standard unit that supports a variety of powerful attachments. It is powered by a Caterpillar C16, 6 cylinder engine and has a 111 litre/hour fuel consumption at full load with 12 hour operating range.

A 50 tonne Rock Hawg TRS 1175, with two operators, was tasked with ripping out the rock either side of the newly installed bridge at Whitwell to form a trench over 100 metres long with an 18 m width. In the 10 day project period, the machine was able to rip out 500 m³ of material effortlessly, with the added benefit of the extracted material being useable for sale - the primary crush material produced by the Rock Hawg can go straight in production without being recrushed. This in itself helped self fund the extraction of the material.

Describing the benefits of this plant Shane Tompkin, quarry manager at Lafarge's Whitwell site, says: "There are two traditional ways of getting stone out: drilling and blasting or mechnically excavating it. The Rock Hawg offers a third alternative to ‘plane' out material."

He continues: "This method was much quicker than any other technique and it provides a good finish with very stable cut faces either side. The process produces good quality material that can be sold, if a market can be found, or reprocessed."

Stage two of the project involves bringing down the level of the current quarry to the haul road, again avoiding blasting and potential quarry fracture close to the bridge area. An 18 m wide trench over 50 metres in length will be completed in 6 days using the new Tesmec TRS 1475 Rock HAwg with two operators, producing more crushed stone and reusable aggregate.

The latest Rock Hawg

Westquay Trading recently introduced the TRS1475 - the first 126 tonne Rock Hawg working in the UK and Europe. Sold to AJ Gammonds the new Rock Hawg is claimed to provide the most powerful trench and excavation machines working in the country.

Having already achieved success with its 50-tonne Rock Hawg  - including the project at Whitwell, AJ Gammonds is the first UK firm to make the investment in the TRS1475. The company believes that adding a powerful 126-tonne model is a natural progression to meet the demands of certain sites.

Tesmec products are well established in large scale civil engineering with a product range that includes chain saws, trenchers and bucket wheels among many other engineering products. In addition to the Rock Hawg, Tesmec manufactures tractor tool carriers, chain saws and Bucket wheels. The Rock Hawg is relatively new technology for demolition, reclamation, civil engineering and utilities industries. In quarries Rock Hawgs have already proved their worth, a viable alternative to blasting in solid rock areas preventing rock fragmentation and ground disturbance - critical for quarry areas.

Westquay Trading Co Ltd
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Appleton Thorn Trading Estate
Warrington
Cheshire
WA4 4ST
UK

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