Lookup NU author(s): Professor Stephanie Glendinning,
Dr Peter Helm,
Dr Mohamed Rouainia,
Dr Ross Stirling,
Dr Paul Hughes
This is the final published version of a report that has been published in its final definitive form by iSMART Consortium, 2018.
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This report provides a summary of the findings from the iSMART project. The research was undertaken because slope deterioration and resultant failures have a significant negative impact on transport networks both in the UK and internationally. An important driver to this loss of performance is weather driven annual cycles of pore pressure change, and anecdotal evidence suggests that extreme weather events contribute to the occurrence of failure. The potential impact of climate change on the rate of deterioration and incidence of sudden failure must be considered. The requirement to better understand the processes that lead to deterioration for varying slope geometries and material types, and for present and future climates mean it was necessary to develop and undertake a combination of laboratory and field investigations, coupled with numerical modelling.Section 2: Better inputs to Models, details the significant multi-scale work undertaken to derive input parameters for advanced models. The investigation of the effect of wetting and drying cycles on soil water retention behaviour demonstrated changes to soil fabric lead to both lower unsaturated cohesion, and changes to water ingress and egress into and from the slope. Major field-scale investigations to measure near surface permeability on both embankment and cut slopes were undertaken, which demonstrated large spatial and temporal variability. This was performed along with advanced 4D geophysical surveys allowing the movement of water within slopes over time to be monitored. Section 3: Calibrated Modelling, provides a summary of activity to calibrate numerical models that can be used to investigate climate impacts on earthwork slopes and specifically to forecast times to failure of slopes that are deteriorating by ratcheting deformations driven by seasonal cycles of weather. The state of knowledge at commencement of the project, which formed the starting point, is briefly explained. The modelling approaches available are discussed, importance of the near surface (e.g. cracking) is introduced, methods for driving the models, including methods and parameters, are presented and the process used to validate the weather driven slope deterioration mechanism is detailed. Finally, an approach for assessing slopes at field scale is explained, including selection of asset data. Section 4: Working with the Models, describes the application of the models, including the method developed for the use of the UKCP09 climate scenarios to generate both present and future weather time series inputs. These were applied as boundary conditions to the model to age the slope, initially to a condition representative of the present. Following this the future climate boundary was applied to assess the effect on further deterioration. From this work preliminary deterioration curves have been derived for specific material and slope types. The work demonstrates the influence of geometry on rate of deterioration, near surface permeability on the time to failure and failure geometry; as well as the influence of effective slope drainage on time to failure.The report concludes that: weather-driven deterioration of soils exists; climate change is likely to accelerate deterioration; and prototype modelling tools to assess future deterioration of transport earthworks have been produced. It points to the potential for further collaborative work both for extending the research and for application of the tools and techniques developed by iSMART to practice.
Author(s): Glendinning S, Helm PR, Rouainia M, Stirling RA, Asquith JD, Hughes PN, Toll DG, Clarke D, Hudson A, Powrie W, Smethurst J, Woodman N, Hughes D, Harley R, Karim R, Dixon N, Crosby C, Dijkstra T, Postill H, Chambers J, Dashwood B, Gunn D, Uhlemann S, Briggs K, Muddle D, Loveridge F
Publication type: Report
Publication status: Published
Online publication date: 01/07/2018
Acceptance date: 02/04/2018
Institution: iSMART Consortium
Notes: Project website: http://www.ismartproject.org/