ONLY THE BEST FOR PORTLAND STONE QUARRY

Masonry stone from the quarries in Portland Island has been used for hundred of years and is a familiar sight on famous structures throughout the UK and particularly in London where buildings from St Paul's Cathedral to the very newest buildings feature it prominently.
    The geological nature of the stone, in its various forms, means it has numerous fault lines, which have always made it a problem to extract. Modern extracting techniques and equipment have made it possible for enterprising companies such as Albion Stone, to acquire and re-open quarries that were previously closed because they were uneconomical to run.
    One such quarry is Fancy Beach, on Portland Island, where a small fleet of highly productive machines is removing overburden to give access to the Portland stone. This is the second phase in developing the quarry. One area is already open and in full production.

Costs Demand Modern, High Production Equipment

To get to the main Portland stone beds involves removing some very hard and unpredictable material. To access the stone, up to 7 m of over burden and sub-standard rock has to be removed. For obvious reasons, this has to be done as economically as possible. The top 1~1.5 m of topsoil and other cover material is being stockpiled. Albion Stone is processing as much as possible of the material being extracted from the various Purbeck cap beds.
   Benches being prepared are dictated by the major joints in the rock, but are typically 20 m x 100 m. The overburden is being stripped off in benches of approximately 3 m.
  The removal of the overburden and cap beds is the responsibility of G. Crook & Sons of Dorchester, who has over 35 years experience in hiring plant and operators. They are providing all the equipment and operators under a long-term hire agreement. When the company started the worked earlier this year, they brought in the latest, most advanced equipment available.
   This material is not suitable as a masonry stone. However, it is suitable for sea defence works and for processing for use as aggregate. The material is too hard to extract directly so a limited mount of high explosives has to be used to loosen the rock.

Modern Equipment For High Productivity

For the work, G. Crook & Son specified machines that could deliver the high level of productivity and reliability demanded

A CASE CX210B equipped with hydraulic breaker is being used to reduce the large dimensioned stone released. At 22.5 t. the CX210B is one of the new series of CASE excavators to feature Tier III engine technology. Taking full advantage of the potential benefits made possible by Tier III engine technology, CASE took the opportunity to fully redesign the hydraulic systems and transmissions to maximise power for increased productivity.
    As a result, although the CX210B has a smaller, albeit extremely strongly built, 4-cylinder engine instead of the previous 6-cylinder, it delivers significantly more power – more than 11% - with fuels savings of up to 20%, a significant consideration when removing a material with little value.
   According to the operator, once you get used to the speed at which works, the CX210B makes a very powerful machine on which to attach a rock breaker. “Getting the large stones in to the best position from which to attack it and being able to put the breaker exactly where you want it is a big feature. It is extremely responsive, and, with the cab door closed, very, very quiet. There very little vibration back into the cab.“
   Alongside the CX210B is a CASE CX700, one of the largest excavators in the CASE range. Because this excavator is being used to load the haul trucks, it demands highly aggressive loading and fast cycle times. The Purbeck stone is very difficult to load because it is very hard and varying in size.
   With an operating weight of 69 t. and power rating of 345 kW at 1800 rpm, the CX700 is ideally sized for this type of application. The bucket breakout force of 29,000 daN gives it the high-power penetration of the material for better bucket loading for fewer cycles. The automatic power-boost function gives 10 second of extra boost when required. “Its very powerful and very quick and more than up to the job,” say the operator.
   When waiting for the haul trucks, the CX700 picks up and position very large dimensions rocks and positions them for the CX210B and breaker to reduce in size.
   The CX700 is being used to load a CASE 340B articulated dump truck, the very first of the new series to be used in production work in the UK. Load, haul and dump work does not come more demanding than working with a hard, abrasive material, in an extremely dusty environment, with haul roads that are narrow, twisting and feature a steep incline.
   With an engine output of 318 kW and payload capacity of 36,000 kg, the CASE 340B is more than a match for the work. Maximum speed is 29.8 km/h and maximum gradient capability is 40%.
   For the operator, this was the first CASE ADT and his initial impressions were very positive. “It is very quiet and seems to have a remarkably fast acceleration. The automatic gear changes are smooth and travelling could not be better. The cab is very comfortable and very effective in keeping out the dust, which is plentiful around here.”

Tough Going

Keeping the loading zone clean is essential as the hard material is very tough on tyres so G Crook & Sons regularly bring in a CASE 921C which is on long term hire to Albion Stone working in the main quarry.
   With a bucket breakout force of 22,804 kg, the 22,961 kg wheel loader can quickly clear the ground and rework the stockpile for easier loading by the excavator.
   After just a few minutes tidying up it is back to the main quarry area where it is used to handle large stone blocks, which demands every bit of the wheel loaders lift and carry capacity. The CASE 921C has a static tipping load of over 20 t.
    G. Crook & Sons have recently added with the very latest in wheel loaders from CASE to its fleet – a 921E.

Developing the Quarry

The Fancy Beach Quarry is a typical Portland stone quarry. The first layer of Portland freestone, beneath the Purbeck caps, is the roach seam some 1 m deep. This limestone, full of shell casts, is a very decorative stone and can be extracted in large dimensions.
    The next layer is a 2 m deep layer of Whitbed, which can be extracted in very large blocks of up to 8 m³. A characteristic of this rock is its very hard weathering characteristics, generally considered to be less than 2 mm per 100 years. It can be intricately carved for statues, sculptures and similar stonework
   Beneath the Whitbed is a layer of softer material. This curf material has very poor weathering characteristics and is not usually quarried commercially. However, it does provide for easy undercutting of the overlying Whitbed material.
   Basebed, which underlies the curf, is what is most recognizable as ‘Portland Stone'. This is the material used extensively for monuments, statues and building facades. Some 2 m deep, this is generally considered the finest, top grade of Portland stone.
   Mark Godden, Quarry and Mine Manager, for Albion Stone, estimates that there is at least 20 years of dimensional stone in the quarry. The commercial grade Portland beds are up to total 9 m in height.
   Conscious of the environment - social and ecological – Albion Stone try to use as little explosives as possible. They have eliminated all use of explosives in the main stone extraction in all their quarries. Explosives are only used, in limited quantities, to loosen material in removing the overburden.
   The preferred option is to use latest technology such as Italian bench saws and hydro bags. “Using this techniques is not only more environmentally acceptable but also gives higher quality stone straight from the quarry. It is quieter, creates less dust to the atmosphere, is much safer and reduces the amount of finishing work. We can also extract stone to customer required dimensions more easily, so there is less waste”, says Mark Godden.
   The blocks at Fancy Beach Quarry can be up to 4 m³. The quarry has 12 people providing stone for the nearby main processing facility where there is up to 50 people employed.
   The Fancy Beach quarry had not been worked for several years, prior to Albion Stone acquiring it. It began production once more at the beginning of 2007 to produce finished masonry stone. “We extract blocks as large as possible from the beds. These can then be cut down to customer requirements using diamond wire saws. Some finishing work can be done in the quarry, however, most of the stone is transported to the nearby production facility,” say Mark Godden
   Albion Stone is committed to using advanced quarrying methods wherever they can. In another of the company's quarries they are actually using underground mining techniques, which has several major environmental benefits, the key one being the fact that it is invisible.

Environmental Concerns

Quarries through Portland Island are subject to very strict environmental regulations. Portland Island is famous for its rare flora and fauna but mostly for its Jurassic fossils – it is generally referred to as England's Jurassic Park.
   As such there are many archaeologists who have to be involved whenever a quarry comes across significant fossil finds.

Proven Expertise In Plant Hire & Quarrying

G. Crook & Sons who are providing the equipment and operators on a long-term hire are familiar with what customers such as Albion Stone require. Established for over 35 years, the company has experience in quarry working, as the company also has its own quarries.
    Apart from excavators, wheel loaders and articulated dump trucks, G. Crook has a substantial fleet of tipper trucks from 4 to 8 wheels as well as grab-trucks and other plant and equipment. They hire equipment with or without operator, for short and long-term contracts.
   Albion Stone was first incorporated in 1927 and opened its first Portland stone quarry in 1979. The company enjoys long mineral extraction leases covering all the Crown Estate's Stone reserves on Portland.
   Their production factory is amongst the largest in the UK, producing a wide range of slabs; ashlar panels for cladding and internal wall lining; pavers and tiles for flooring as well as the intricate masonry for prestigious new construction or in vital restoration work of historic monuments.
   The company has invested over £1.5 million in re-opening and developing the Fancy Beach Quarry.