GEOTECHNICAL ENGINEERING
New technologies for embankment warning systems
Vulnerability to climate change
N
David Gunn: Leader of the Geotechnical- Geophysical Properties and Processes Team
ear-term development of transport
infrastructure must
include technologies that will allow us to assess the resilience of the network to increased temperatures and precipitation predicted by the UK Climate Change Impacts Programme (UKCIP).
Climate change impacts on transportation networks are not simply a function of weather events but also of the infrastructure’s condition and vulnerability, which varies greatly across the transportation network. 18th expansion, 19th
century waterway century railway
Jon Chambers: Senior Research Geophysicist
expansion and post war highways expansion all included construction of large earth embankments, whose properties and structure depends upon original construction methods and long term ageing.
In particular, older, waterway and railway embankments deviate from the conceptual layered model because of the tipping methods used in their construction.
The distribution of Phil Meldrum: Senior Research Engineer
composite materials within the embankment controls engineering performance, especially, the spatial and temporal variation of groundwater and its influence upon key geotechnical properties controlling strength and stability.
Richard Ogilvy: Leader of the Geophysical Tomography Team
80 rtm
Climate resilience planning for transportation networks will require technologies which can provide a rapid, volumetric, and
Modern, compacted clay embankments are prone to near- surface problems associated with shallow moisture ingress, whereas water can drain deeper into older Victorian and Georgian embankments causing far greater moisture content fluctuations in the embankment core (Gunn et al. 2007, 2009).
Repeated cycles of wetting and drying within the core of these embankments are driving long
hence holistic, assessment of infrastructure condition. Key to this process will be adaptive technologies delivering real- time images of the true 3D spatial variation of groundwater and geotechnical properties affecting stability.
While providing useful ground truth, a full understanding of vital ground processes with sufficient temporal and spatial resolution is often not possible from invasive investigation alone.
We assert that this role can be filled by non-invasive geophysical methods that not only provide real-time images of moisture movement but are also calibrated so as to indicate full 3D, quantitative geotechnical property changes.
This can be achieved if the relationships between geophysical properties, such as electrical resistivity and geotechnical properties, such as moisture content, pore pressure and strength are well understood.
Moisture movement and embankment ageing
term processes leading to the progressive deterioration of material integrity, collectively referred to as “ageing”. Gradual loss of strength in clay due to irreversible plastic strains related to repeated shrinkage and swelling is probably most well known (Terzaghi and Peck, 1948).
Other moisture-driven processes are equally important to ageing but can be specific to the litho- stratigraphy of the source material. For example, fabric micro-voiding and rupture is associated with fill sourced from mudrocks including significant evaporite deposits, such as the rocks from the Permo-Trias and Lias covering much of central England (Gunn et al. 2007, 2009).
Aged infrastructure comprises unique heterogeneity that cannot be easily modelled and therefore deterioration must be monitored in situ. A full climate vulnerability assessment requires knowledge of the condition the embankment is in, where this condition fits within the progressive deterioration life-cycle and how close this point is to any threshold condition that would trigger rapid instability.
Maintenance strategies based only upon surface morphological observation may detect late- stage manifestations associated with internal failure, but invariably fail to give sufficient or timely warnings for effective intervention.
Monitoring with point-sensors alone provide insufficient sampling to fully capture
Oct/Nov 10
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