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The Research Challenges

Structuring the research

Current techniques can estimate future rates of deterioration that might lead to failure in transport infrastructure slopes, but are difficult to scale up, do not capture all drivers of deterioration relevant to all LLAs, are poor at dealing with uncertainty and heterogeneity, and lack rigorous validation against representative field data.

ACHILLES will build on and enhance the core consortium’s complementary skills, deep understanding of the problem, reputation and the momentum of industry interactions.

As deterioration is currently an industry top priority concern we will link into ongoing industry-driven projects. The timing of the development of the National Infrastructure Commission assessment method provides a further opportunity to maximise impact.

The functioning of infrastructure systems is dependent upon the ground beneath or around its assets (e.g. pylon, pipe or rail track). Tools to assess, monitor, design and repair the performance of the ground are fundamental. ACHILLES will deliver these tools through three Research Challenges as shown below.

The three research challenges superimposed on a generalised deterioration model for transport earthworks (adapted from Thurlby, 2013)

Research Challenge 1: Deterioration processes

RC1 will provide understanding of material scale deterioration – from nano (surface chemistry of clays) through to macro (lysimeter) scale. The current state-of-the-art does not consider cross scale conceptual models of deterioration; existing constitutive models are severely limited in their ability to capture deterioration. Earth assets suffer deterioration resulting from fissuring, loss of suction, chemical changes (weathering), and cyclic development of shear strain. The new insights into deterioration processes will be used to develop performance curves for a range of engineering geo materials, performance indicators (such as strength, stiffness and permeability) and (novel) material-scale mitigation measures.

Research Challenge 2: Asset Performance

RC2 will challenge current understanding of deterioration mechanisms at the asset scale, building on long-term monitoring of full-scale assets, stakeholder performance data and coupled numerical modelling (developed in previous research and enhanced by RC1). New asset systems (e.g. buried pipe, flood embankment) will be considered, and new sensors / sensor networks will be added. Evidence-based performance curves for a range of exemplar single assets, strategies for asset-scale deterioration detection, assessments of engineering performance, and design mitigation measures will be produced.

Research Challenge 3: Forecasting and Decision Support

Research Challenge 3 will utilise hierarchical Bayesian modelling to synthesise multiple available data sources with physical models to properly quantify uncertainty for predictions at the network scale. When combined with a deeper understanding of asset-owner decisions, RC3 will develop appropriately calibrated forecast models and probabilistic ranking of potential network-scale interventions to enable optimisation of investment strategies. The cost of (obtaining) different forms and quantities of data, and the reliability of the information it can provide, will be placed in the context of the cost and risk of different decisions

An outline of the challenges and research phases of the Programme Grant. Phase 1 will be completed in 2020. Evaluation of research developments and outcomes will lead to assessments of the focus, scope and impact of the research direction and the setting of a new series of priorities that will lead us into Phase 2.

MindMapping deterioration and performance

In ACHILLES we use the term ‘deterioration’ to describe a change leading to a loss of performance with respect to an expectation. At an early stage in the programme a MindMap was created to categorise evidence of soil and slope deterioration and to guide ACHILLES research activities.

Within the MindMap, ‘deterioration’ was used to describe a reduction in strength, stiffness, permeability or structure of a soil or slope in response to weather-driven pore water pressure changes. This has been used to form a conceptual model of deterioration consisting of four categories (shown as quadrants) containing statements about the nature of deterioration, that are supported by published evidence. These are (i) Micro-scale deformation & breakdown, (ii) Macro-scale deformation, (iii) Change in soil hydraulic properties, and (iv) Change in soil strength and stiffness.

The conceptual model allows the ACHILLES team to ensure that planned research activities and outputs are co-ordinated around a common understanding of deterioration. It has allowed the team to identify key research gaps and to develop cross-cutting activities that explore deterioration processes across material scales and modes of investigation (e.g. field and laboratory testing).