Product category:
Building Energy Efficiency and Sustainability
News Release from: Ashtead Technology Rentals | Subject: Remote visual inspection system
Edited by the Buildingtalk Editorial
Team on 27 November 2007
Hired remote control camera reveals
secrets
Specialist provider of rental instruments, Ashtead Technology Rentals help English Heritage safely study the internal condition of a 4,400 year old hill in Wiltshire.
Silbury Hill near Avebury is the tallest prehistoric man-made mound in Europe and one of the world's largest It has long been the source of great fascination and the main purpose of the mound is still unknown to this day
This article was originally published on Buildingtalk on 7 Oct 2008 at 8.00am (UK)
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A number of investigations have taken place in recent centuries, some of which have given rise to collapses at the mound's surface, and English Heritage is currently undertaking a major programme of stabilisation.
Naturally such work is potentially hazardous and a robotic crawler known as a Rovver has been hired from Ashtead Technology Rentals to facilitate the safe investigation of the old excavations.
Commenting on the internal investigation work at Silbury Hill, English Heritage Conservation Engineering Technician Arthur McCallum said, "The initial use of the Rovver was to scan the roof of the tunnel as this would be exposed in advance of human access".
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Credit crunch drives market for hired instruments
Ashtead Technology Rentals reports high demand for instruments for environmental monitoring, for health and safety checking, for testing materials and for remote visual inspection in construction.
Monitoring contamination without excessive cost
James Carlyle from Ashtead Technology Rentals, explains why the requirement for environmental monitoring data to be reliably accurate has never been greater.
Renting high value inspection equipment.
Test and inspection engineers use Ashtead Technology Rentals to experience the benefits of hiring over purchasing on a range of Olympus Industrial Iplex Videoscope products.
"Once scanned, the roof would be sheeted and the process would be repeated as the tunnel advanced towards the centre".
"In addition, it was anticipated that small side cavities, too small or unsafe to enter, would be investigated by the Rovver, which would scan and assess the size /condition of the voids".
"As with most things this is not quite how it turned out in practice, the roof was scanned at the start but conditions meant the roof was sheeted in advance so it was not possible to scan the whole roof as planned".
"There were no small side voids because, over the years, the hill had squashed them shut".
"The Rovver was of greatest value in work on top of our tunnel roof to investigate and scan the large voids where it was not safe or large enough for human recording." Ashtead General Manager James Carlyle is delighted to learn that the Rovver has been so useful at Silbury Hill, but says he is "not surprised because the Rovver is extremely robust and has been popular in a wide variety of applications".
"It was initially designed for the investigation of pipes and drains and as such it likes wet dirty conditions, so we have customers using it for the remote visual inspection of pipes, drains, tunnels, voids and chambers - the list is endless".
"The Rovver itself is quite high-value but it lends itself very well to renting because it provides our customers with access to the latest technology without the burden of capital cost".
Silbury Hill was built about 4,400 years ago in the Neolithic period.
It stands at 30 metres high and 160 metres wide, covering an area almost as large as two football pitches.
Its construction is estimated to have involved roughly 4 million man-hours and 500,000 tonnes of material; mostly chalk, quarried and cleared from the surrounding terraces and ditches.
No one knows why Silbury Hill was built, but we do know that it was during a time of great change in the prehistory of Britain.
Recent radiocarbon dating has shown that it was built as the Neolithic period, or 'New Stone Age', gave way to the Bronze Age.
This time was characterised by the introduction of many new practices to Britain, such as widespread individual rather than communal burial, the use of metal and the production of new forms of pottery.
The first purposeful excavation of Silbury Hill was undertaken by a team of Cornish miners, led by the Duke of Northumberland in 1776 and a number of further investigations have taken place since that time.
Few prehistoric artefacts have ever been found on Silbury Hill; at its core there are only flints, moss (still green!), freshwater shells, sarsen stones and antler picks.
Roman and medieval items have been found on and around the site since the nineteenth century and it seems that the hill was reoccupied by later peoples.
After heavy rains in May 2000, a collapse of the 1776 excavation shaft caused a hole to form in the top of the hill.
English Heritage undertook a seismic survey of the hill to identify the damage caused by earlier excavations and determine the hill's stability.
Repairs were undertaken, though the site remains closed to the public.
English Heritage's archaeologists also excavated two further small trenches as part of the remedial work and made the important discovery of an antler fragment, the first from a secure archaeological context at the site.
This produced a reliable radiocarbon date of c.
2490-2340 BC, dating the second mound convincingly to the Late Neolithic.
Other recent work has focused on the role of the surrounding ditch which may not have been a simple source of chalk for the hill but a purpose-built water-filled barrier placed between the hill and the rest of the world.
In March 2007, English Heritage announced that a Roman village the size of 24 football pitches had been found at the foot of Silbury Hill, containing regularly laid out streets and houses.
On 11 May 2007, Skanska under the direction of English Heritage, began a major programme of stabilisation work to Silbury Hill with the tunnels and shafts being filled with hundreds of tonnes of chalk.
Alongside the repair work a new archaeological survey is being conducted using modern equipment and techniques including the Rovver remote control crawler camera.
As part of the stabilisation process, Skanska Civil Engineering is undertaking three main tasks: 1) A temporary scaffold ramp and building has been erected at the entrance to the horizontal tunnels dug into the Hill in 1849 and 1968.
These tunnels will be emptied and then permanently filled with compacted chalk.
2) Once the horizontal tunnels have been filled, the polystyrene blocks that have been temporarily placed in the large crater on the summit will be carefully removed.
The shaft will be filled with chalk brought up to the top of Hill using a rail track.
3) A line of craters on the hillside has been created by subsidence into the horizontal tunnels below.
The craters will be packed with chalk once the tunnels beneath have been permanently filled.
All the filling will be done with exactly the same type of chalk that was used to build the mound in the Neolithic period.
Once the work is complete, the Hill will have been restored to as near its original condition as possible and the Rovver robotic crawler will have to go back to its normal work - inspecting drains.
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