GEOTECHNICAL ENGINEERING
Fig. 2. Flooding deep into East Leake embankment during 2007 record rainfall summer
customised to capture processes and changes specific to each embankment.
With unprecedented spatial- temporal sampling capabilities, the system will provide prognostic insight into the impact of extreme events such as sustained drought or floods.
Early electrical imaging trials at East Leake have aided the identification of sand and gravel lenses within predominantly mudstone fill (Chambers et. al 2008, Gunn et al. 2008).
But most significantly, differential resistivity images have led to the identification of groundwater movement as a series of wetting and drying fronts moving through, and penetrating deep into the core of the embankment.
Fig. 2. Flooding deep into East Leake embankment during 2007 record rainfall summer.
Fig. 2 shows how the record- breaking rainfall during the 2007 summer led to the gradual infiltration and full saturation of the east flank of the embankment (left side).
In fact, the infiltration zone is up to 7 m deep, extending into the underlying Cropwell Bishop
82 rtm
Formation, implicating bedrock processes as part of the drainage problem.
During these flood events, standing water develops in this area at the toe of the east flank.
Consequently, this has the potential for climate-induced instability.
The existing 2D array will be extended into 3D coverage in September 2010 so that the vertical and lateral ground water movement can be understood enabling new concept for focused drainage measures to be considered.
Future developments
ALERT-ME brings together the transportation geotechnics and geophysical tomography teams at the BGS.
We will report our progress and disseminate results through key industry events and publications.
We will also develop the ALERT- ME web site to support the project and inform industry.
ALERT-ME has an industrial steering group to help focus applications in the transport sectors, which includes representatives from the Great
Central Railway (Nottingham) Ltd., Network Rail, London Underground Ltd., British Waterways and G. Underwood Ltd.
We have also enlisted the support of the Transport iNet to run a knowledge exchange event in 2012 to showcase ALERT- ME and maximise its potential impact to a wider stakeholder audience across the transport sectors.
Acknowledgements
This article was published with the permission of the executive director of the British Geological Survey, NERC.
References
Chambers, J E, Gunn, D A, Wilkinson, P B, Ogilvy, R D, Ghataora, G S, Burrow, M P N & Tilden Smith, R, (2008). Non- Invasive Time-lapse Imaging of Moisture Content Changes in Earth Embankments Using Electrical Resistivity Tomography (ERT). In: Ed. Ellis, E., Yu, H.S., McDowell, G., Dawson, A. & Thom, N. Advances in Transportation Geotechnics. Proc. 1st Int. Conf. Transportation Geotechnics, Nottingham, Aug 2008, pp 475-480.
Gunn, D.A, Reeves, H., Chambers, J.E., Pearson, S.G., Haslam, E., Raines, M.R., Tragheim, D., Ghataora, G., Burrow,
FOR MORE INFORMATION
To find out more about ALERT-ME or register interest in the forthcoming ALERT-ME knowledge exchange event, please contact:
Dr. David Gunn
Geotechnical and Geophysical Properties and Processes Team T: +44 (0) 115 936 3400 E:
dgu@bgs.ac.uk
Dr. Richard Ogilvy Geophysical Tomography Team T: +44 (0) 115 936 3359. E:
rdo@bgs.ac.uk
Oct/Nov 10
M, Weston, P., Thomas, A., Lovell, J.M., Tilden Smith, R., Nelder, L.M., (2007). Assessment of embankment condition using combined geophysical and geotechnical surveys. Proc. 9th Railway Engineering, London.
Int. Conf.
Gunn, D.A, Reeves, H., Chambers, J.E., Ghataora, G., Burrow, M, Weston, P., Lovell, J.M., Tilden Smith, R., Nelder, L.M. & D Ward, (2008). New geophysical and geotechnical approaches to characterise under utilised earthworks. In: Ed. Ellis, E., Yu, H.S., McDowell, G., Dawson, A. & Thom, N. Advances in Transportation Geotechnics. Proc. 1st
Int. Conf.
Transportation Geotechnics, Nottingham, Aug 2008, pp 299-305.
Gunn, D.A, Haslam, E., Kirkham, M, Chambers J.E, Lacinska, A, Milodowski A, Reeves, H, Ghataora, G, Burrow M, Weston, P., Thomas. A., Dixon, N., Sellers, R. & Dijkstra, T., 2009. Moisture measurements in an end-tipped embankment: Application for studying long term stability and ageing. Proc. 10th London.
Int. Conf. Railway Engineering,
Terzaghi, K. and Peck, R.B., 1948. Soil Mechanics in Engineering Practice. Jon Wiley, New York.
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