RAIL SURVEYING
Brighton station cliff monitoring
Richard Cordier, operations manager at Vision, describes a recent project and how new technology overcame some technical challenges.
As
part of the Earthworks Monitoring (Southwest Territory) contract, our client MLM Consulting Engineers Ltd (working on behalf of B&M McHugh Ltd) tasked Vision with monitoring the movement of two areas of cliff face, both adjacent to Brighton Station, in a safe and controlled manner.
This initially presented Vision with three issues that we had to overcome: the method of measurement in terms of the actual cliff face; the issue regarding the safety of our engineers carrying out this work; and doing this whilst not causing any disruption to the train services utilising the adjacent tracks.
Vision, in partnership with Leica Geosystems, presented an innovative method to eliminate the health and safety risks traditionally associated with this type of work, safeguarding our engineers and preventing any disruption to train services by using a new instrument, the Leica NOVA MS50.
With this new technology, our engineering surveyors were able to provide a solution that
would fulfi l all the requirements of our client. Other benefi ts realised whilst undertaking this work were:
• Improved effi ciency and accuracy of measurement
• Reduction of time on site
• Substantial cost savings to the end client (Network Rail)
With this new instrument, the LEICA NOVA MS50, Vision was able to undertake the monitoring by scanning the cliff from a series of positions away from the track. Each position was referenced to a network of control points created with the same instrument, allowing the scans to be based on the same reference, later,
after processing the data.
Subsequent visits to the site at an agreed time allowed future scans to be overlaid on the previous scans, so a comparison could be made and any movement in the cliff face identifi ed.
The advantages of using the LEICA NOVA MS50 – basically an ‘all-in-one’ instrument
– were that Vision was able to set up the network of control
points, process the
results, do a basic topographic survey of the boundary of the site, process the data, and fi nally (on the same set-up) carry out a laser scan of the cliff faces. By being able to process the scanning data on site using the instrument screen, we were able to confi rm and check that all areas relating to this project had been captured, by viewing a 3D overview of the scan, before fi nally leaving site.
The precision in terms of the monitoring had been specifi ed as detecting any movements higher than 10mm
over
a
given period of time. The Leica NOVA MS50 was more than capable of meeting and exceeding the required specifi cation and is a fantastic addition to Vision’s arsenal of equipment.
FOR MORE INFORMATION
E:
sales@vision.co.uk W:
www.vision.co.uk
Image above: Differences between two sets of scans readings at the cliff; movements represented in different grade of colours in the scalar fi eld
86 | rail technology magazine Dec/Jan 14
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