Award-winning papers in 2010

The Crampton Prize, presented for the best paper on practical geotechnical engineering, was awarded to: Roscoe H and Twine D (2010) Design and performance of retaining walls. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering 163(5): 279–290, http://dx.doi.org/10.1680/geng.2010.163.5.279.

Embedded retaining walls for 1·8 km of cut-and-cover tunnels and earth-retaining structures were redesigned during the construction period to optimise construction methods and temporary propping. The design approach included many of the developments now recommended in Ciria report C580, and the paper summarises the experience gained on this contract. The site team made detailed observations of the performance of all 14 structures during construction, and this paper gives an overall summary of the wall movements and prop loads that were measured. The walls were surcharged, and none of the props was preloaded. Despite this, the maximum movements were within those estimated from published correlations. Wall movements were time dependent, and occurred at rates of up to 0·2 mm/day. Prop loads were generally about 40% of the values obtained from moderately conservative calculations. Reducing the prop stiffness assumed in calculations improves agreement, and measurements are reported that provide a basis for closer appraisal of this aspect in future designs.

The John Mitchell Medal, presented for the best paper in geotechnical practice, site-based innovation or geotechnical safety, was awarded to: Hendry M, Hughes DA and Barbour L (2010) Track displacement and energy loss in a railway embankment. Proceedings of the Institution of Civil Engineers – Geotechnical Engineering 163(1): 3–12, http://dx.doi.org/10.1680/geng.2010.163.1.3.

The mainline railway track between Dublin and Belfast was constructed during the 1850s, with substantial lengths of railway embankment constructed over soft, peaty soils. In recent years Northern Ireland Railways (NIR) has noticed that the sections of the railway track constructed on these peaty soils have been deteriorating at an increasing rate. Train speeds have been reduced in response to concerns that cyclic track displacements appear to be increasing over time in response to train loading. Track maintenance has also increased significantly. The research described in this paper was undertaken to quantify the response to cyclic train loading of two portions of this track founded on peaty soils. Track displacements were recorded using a sensor system specifically created for this project. The sensor consisted of a photosensitive array, mounted on the sleepers, and a laser, which was targeted onto the photosensitive array from a location outside the area of influence of train loading. Track deflections from 5 to 20 mm were measured under train speeds from near zero to over 120 km/h. The temporal variation in track displacement was used to calibrate an analytical (Winkler) model. This analysis suggests that the deformation of the embankment under train loading was not due to dynamic excitation but rather to static deformation of the poor-quality fill and soft foundation materials. As a consequence, the analytical model highlighted that train speed has limited effect on the magnitude of the deflection of the embankment within NIR operating speeds, but has the potential to significantly reduce the power lost to the damping within the embankment and subgrade.

Crampton Prize winners Howard Roscoe and David Twine with ICE President Peter Hansford

John Mitchell Medal winners Lee Barbour, David Hughes and Michael Hendry with ICE President Peter Hansford