GEOTECHNICAL AND TRACK ENGINEERING
Pushing performance L
Carlton Hall, engineering director at Lankelma, explains more about its recent geotechnical data acquisition work.
ankelma has had a busy 12 months applying cone penetration technology
to the ground investigation challenges of the rail environment. This specialist ground investigation technique, which enables a high volume of geotechnical data to be acquired over short possession times, has contributed to the provision of high-resolution soil profi les and engineering parameters to design teams charged with delivering solutions for rail upgrade works.
Core to the service has been the bespoke road- rail rig which, working in the four foot, has undertaken in excess of 40 shifts over the last year on projects ranging from Paisley Corridor, Scotland to Stockley Junction in southern England. Currently the truck is servicing the Great Western Electrifi cation and East-West Rail projects.
A smaller, more versatile CPT rig attached to a rail excavator arm has also seen recent effective use in the rail environment. Well-
Above: Scremerston
“The distinction is that a wash-out failure is typically due to material fl owing over ground and earthfl ow is typically as a consequence of ground water building up within the cutting slope and fi nally reaching a level where it turns the material on the slope to liquid and that fl ows onto the track,” he explained.
Extreme weather events this summer, such as excessive rainfall, led to groundwater topping up too quickly, leading to earthfl ow-type failures on the Cumbrian coast.
Network Rail is currently funded to maintain its assets’ condition, where around 2% fall into the ‘poor’ condition, 48% in a ‘marginal’ state, and approximately 50% that are ‘serviceable’.
The commitment with the regulator is to broadly maintain the number of assets in each category.
Harms said: “Weathering affects it; the condition of the asset is gradually worsening all the time. We’re trying to bring it back up to an as-new condition or a well-serviced condition.”
Hazard and risk
Network Rail currently manages earthworks through an annual examination programme which scores each earthwork on criteria such as height, angle, composition, extent of
burrowing, degree of vegetation cover and likelihood of water being concentrated.
This data is run through a calculation to identify the condition of the slope, or the hazard it presents of failing. Then other factors, such as proximity to the railway, line speed, complexity of layout and the level of consequences if an incident were to occur are put into an earthworks prioritisation model, which determines the areas to be prioritised for treatment and management.
Harms explained: “The hazard remains the same if it has the same features, but the risk is clearly far less if it’s nowhere near the railway.”
Earthworks are generally sorted into four categories on intervention; an emergency situation which requires an immediate response to failure, a hazard that presents a high risk but which can be monitored, a longer-scale monitored response and fi nally the background remedial works to maintain asset condition. The time taken to develop and apply solutions to such hazards range from one week interventions to two years of monitoring through topographic surveys, inclinometers and ground models.
Scottish signatures Discussing interesting developments in remote
condition monitoring, Harms highlighted a trial in Scotland which is seeking to identify vibration patterns associated with boulders falling, in order to warn the railway of a hazard or incident.
The trial is an updated version of a system that used trip-wires to set signals to ‘danger’ if activated.
The new listening cables are made up of fi bre- optics which feedback a standard interference pattern, that changes if signifi cant vibration – such as that caused by a rolling boulder – is picked up in its vicinity.
Harms said: “The intention is to try to pick up the signature of a boulder rolling down the slope or hillside, and that technology could be very effective. We are watching with interest to see what the conclusions are and ultimately what the cost of installation could be.
“Because if it is a more cost-effective way of managing the risk of failure at critical locations, then we would be very interested in installing something similar, say on approach to tunnels or locations where if the train did come off, it would have a much greater consequence.”
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suited to diffi cult access locations away from the running lines, the rig has investigated problems relating to structural foundations, sub grade, marginal slopes and retaining walls.
A good example of effi cient rail investigation services was demonstrated during Easter this year. As part of an intensive investigation managed by Geotechnics Ltd, our CPT rigs were used on diffi cult ground between Plumstead and Abbey Wood in south east London.
CPT instrumentation comprising piezocone and magnetometer enabled detailed ground profi ling plus UXO clearance at each test location to be
undertaken within the public holiday line closure window.
FOR MORE INFORMATION
T: 01797 280050 E:
info@lankelma.com W:
www.lankelma.com
Carlton Hall
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