Railway Geotechnics and Geophysics

Efficient rail performance requires that constant and level rail track geometry be maintained. The geotechnical properties of the subgrade exert huge control over the performance of our railway network. Efficient running of the existing network and plans to upgrade operational and abandoned infrastructure are high on the agenda. Now, more than ever, the rail network urgently needs fundamental research into the performance and properties of the subgrade particularly within drift geology and engineered structures constructed in Victorian times. While much data can be gathered using traditional site investigation methods, the BGS is actively involved in developing new techniques to measure and assess subgrade properties for the benefit of the whole network.

Our Railway Geotechnics and Geophysics Team offers services covering:

stiffness modelling of the subgrade
geological evaluation of the subgrade
ground evaluations for route planning
geophysical monitoring of track and subgrade performance.

Investigation at the East Leake Research Site.

Investigation techniques at research sites such as Leominster and East Leake include:

sleeper acceleration
subgrade dynamic loading
subgrade stiffness studies
dynamic cone resistance
electrical resistivity surveys
microtremor surveys.

Continuous surface wave investigation of subgrade stiffness at the East Leake Research Site

Research and partnerships
The BGS is leading teams including the Great Central Railway (Nottingham) Ltd., the Nottingham Transport Heritage Centre, and the Railway Research Centre at Birmingham University in the management of railway research sites where new methods are evaluated.

Railway research sites
At Leominster our team is pioneering new techniques to measure dynamic loads from rail traffic. A vibration amplification phenomenon has been detected that has significant implications for the subgrade problems that develop due to repeated traffic loading. Increased vibrations detected deep within the subgrade are shedding new light on the processes by which fine-grained material is transported into the ballast.

Dynamic load from a dual carriage DMU in subgrade showing load increase with depth in poorly drained alluvial soil, resulting in migration of fines into the ballast from soft clay at the top of the subgrade.

At East Leake, Notts our team is developing new techniques to characterise the condition and performance of engineered embankments. We've combined traditional site investigation techniques with new advances in resistivity surveying and continuous surface wave surveys, and are pioneering new applications of microtremor studies to investigate the distribution and variability in the geotechnical properties of engineered fill.

Comparison of the stiffness and friction ratio of the ballast, underlying fill and the geological formation (deeper than 5.5 m ). The shallow interval of higher stiffness / lower friction ratio lens from station 40 m is due to a change from clay to sand and gravel fill materials.

3D geospatial models for route appraisals:
Network maintenance programmes can be improved with better integration of geological data from regional to site scales. Attributed data now held in 3D geospatial databases can be combined in rating schemes designed to identify areas where ground conditions are difficult and likely to cause subgrade problems. Studies undertaken in Manchester, London and Glasgow, where 3D models already exist, show the relevance of this approach for linear route appraisal.
These studies produce:

detailed geological sections along railway routes
identify problem soils at outcrop and subcrop
produce data applicable at regional and site scale
use the latest digital terrain models
correlate problem soils directly with track geometry
selectively evaluate geotechnical properties along the route to identify sections of poor track
give engineering geological assessments
enable assessments of made ground.

Geological and engineering geological linear route assessment related to track geometry.

Selected Publications

Gunn, D A, Jackson, P D, Entwisle, D C, Armstrong, R W, and Culshaw, M G. 2003. Predicting subgrade shear modulus from existing ground models. NDT&E Int. 36, (3), 135-144.

Gunn, D A, Nelder, L M, Jackson, P, Entwisle, D, Stirling, A B, Konstantelias, S, Lewis, R W, and Kingham, P. 2004. Geophysical inspection of the trackbed-subgrade stiffness and performance. 7th Int. Conf. Railway Engineering.

Gunn, D A, and Stirling A B. 2004. Geophysical trackbed and subgrade monitoring at Leominster Station. Rail Technology Magazine, 4, (6), pp 34-37.

Gunn, D A, Nelder, L M, Chambers, J E, Reeves, H, Freeborough, K, Jackson, P, Stirling, A B, and Brough, M. 2005. Geophysical monitoring of the subgrade with examples from Leominster. 8th Int. Conf. Railway Engineering, London.

Gunn, D A, Nelder, L M , Ghataora, G, Stirling, A B, Konstantelias, S, and Burrow, M. 2006. Geophysical properties of the railway subgrade at a site in Leominster. Jour. of the Permanent Way Institution.

Gunn, D A, Nelder, L M, Chambers, J E, Raines, M R, Reeves, H J, Boon, D, Pearson, S, Haslam, E, Carney, J, Stirling, A B, Ghataora, G, Burrow, M, Tinsley, R D, Tinsley, W H, and Tilden-Smith, R. 2006. Assessment of railway embankment stiffness using continuous surface waves. Proc. 1st Int. Conf. Railway Foundations, Birmingham, September 2006.

Nelder, L M, Gunn, D A, and Reeves, H. 2006. Investigation of the Geotechnical Properties of a Victorian Railway Embankment. Proc. 1st Int. Conf. Railway Foundations, Birmingham, September 2006.

Reeves, H J, Kessler, H, Freeborough, K, Lelliot, M, Gunn, DA, and Nelder, L M. 2005. Subgrade geology beneath railways in Manchester. 8th Int. Conf. Railway Engineering, London.

For further information contact: enquiries@bgs.ac.uk

See also