## 1 Introduction  
The performance of geostructures in the UK's transport network is significantly impacted by their construction age. A considerable portion of railway geostructures were constructed in the late 19 th and early 20 th century [1]. These structures were empirically designed, resulting in variable geometry and material compositions and were often associated with inadequate compaction conditions producing large, short-term deformations and excessive settlement [2, 3, 4]. Early Victorian-era construction was later followed by the rapid growth of highway geostructures between the 1960s and 1990s. Their design contrasts with previous efforts due to the utilisation of modern techniques such as limit equilibrium methods and principles of saturated soil mechanics [5]. Demand for transportation thereafter continued, with railway passenger numbers in 2019 twice those of the inter-war period [6]. This makes historic geostructures, which would be considered poorly constructed by contemporary standards, integral to the UK transport network. However, due to their poor construction, deterioration linked to the formation of internal pore pressures driven by atmospheric changes has been shown to impact their performance. This makes them comparatively more vulnerable when contrasted with the modern construction techniques used on the UK highway network [7]. Furthermore, it is likely the UK will experience more extreme weather conditions with reference to past climatic trends, due to climate change [8]. A comparison between rainfall and geostructure failures by Network Rail showed a strong correlation between both variables for data between 2003 and 2020 [9]. It is therefore probable that these predicted climatic changes will result in performance shortcomings of historic structures owing to unprecedented changes in hydraulic stresses. Consequently, there may be loss of productivity, increased costs, and disruption to the UK transport network. As of late 2020, these issues have been further brought to national attention by the fatal railway derailment at Stonehaven, where an interim report by Network Rail acknowledged that the effects of climate change are progressing faster than initially anticipated [9; 10; 11; 12]. Geotechnical assets, often referred as 'geostatures', are primarily split into embankments and cuttings, but also can form smaller-scale works for widening, diversions, site filling, or levelling [13]. They are fundamentally used to maintain formation level and provide a stable platform for placement of road-pavement or railway. In addition, embankments must also minimise differential settlement; this is especially important for railway infrastructure which has a small tolerable differential settlement limit--usually up to five millimetres between running rails [14]. Cuttings can be formed in soil or rock; requiring the stabilisation of side slopes to ensure debris does not impede traffic. Network rail alone oversees a portfolio of 190,000 earthwork geostatures (assets) of approximately 19,000 km in length, which requires continuous asset management. As of 2012, a specific earthwork risk-based management system was implemented to identify at-risk earthworks to target interventions. The system is constantly being developed to increase resilience of the network to extreme weather [15]. This encapsulates several broad vulnerabilities and allows for a general differentiation between geotechnical risks posed by different assets. However, recent research has also shown that the response of compacted soils is influenced at a micro scale by the arrangement of the pore structure resulting from its initial conditions and evolution [16; 17; 18; 19]. The historical legacy of geostructure construction in the UK requires particular attention, as it has implication for both present and future performance of the transport network.