Climate change will affect our aging transportation and flood defence earth infrastructure (embankments, cuttings, slopes adjacent to transport corridors). Infiltrating rainwater/floodwater increases pore-water pressure leading to a reduction in soil shear strength eventually triggering slope instability. Dry/wet periods cause shrink/swell behaviour of clayey geostructures and may contribute towards these geostructures reaching the serviceability limit state.

Ground-atmosphere hydraulic interaction is almost always mediated by a vegetated interface. If adequately ‘engineered’, it can be transformed into a valuable climate change adaptation measure for long linear infrastructure subjected to climatic hazard. Vegetation-based solutions are:

• relatively easy to implement over long distances,
• ‘climate-smart’ due to plant phenotypic plasticity in a changing climate
• carbon neutral/negative.

This lecture will present experimental and numerical evidence showing that transpiration-induced suction (hydrological reinforcement) and lateral drainage promoted by the higher hydraulic conductivity of the root zone (hydraulic reinforcement) can considerably affect the stability of slopes. It is also shown that increasing (e.g., due to vegetation growth) or decreasing transpiration (e.g., due to clearing) can lead to excessive deformations of the clayey geostructure.

These processes occur in the Soil-Plant-Atmosphere Continuum (SPAC) and can possibly be amplified or attenuated via the biotic and abiotic manipulation of the SPAC. This is an approach commonly adopted in agriculture and forest management and the event will discuss the lessons we can learn from plant science to develop geotechnical solutions.

Vegetation and soil microbiota live in a complex evolving ecosystem, and post-intervention field monitoring is required to assess the performance of any nature-based adaptation measure (i.e., the observational method is an intrinsic part of ‘designing with nature’). Field monitoring is also key to characterise the SPAC. We cannot bring large ‘representative’ samples of vegetated interface to the laboratory, instead we need to move our laboratory to the field. The lecture will address the challenges and opportunities in the monitoring of the SPAC.

Finally, the lecture will highlight the problem of designing hydrological reinforcement of slopes via a transpiration model designed to be physically-based in order to guide the choice of suitable plant functional traits.

Professor Alessandro Tarrantino is Professor of Experimental Geomechanics from the University of Strathclyde.

The common denominator in his research is the presence of at least two fluid phases (liquid and gas) in the medium pore space. Under these conditions, different physical processes with high level of coupling (liquid flow, vapour flow, heat transfer, and solid matrix deformation) control the hydraulic and mechanical behaviour of the porous medium, which is therefore relatively complex to investigate and model.

In Civil and Environmental Engineering, multiphase (unsaturated) porous media are typically encountered in the upper portion of the soil profile, between the ground surface and the ground water table/phreatic surface. Processes occurring in this zone are therefore the focus of my research, and includes rainwater infiltration, groundwater recharge, pollutant transport, soil shrinkage and heave, surface cracking, soil subsidence, and subsurface water flow and runoff (i.e. flood formation), and shallow landslides. Most of these processes have an interaction with the atmosphere and are therefore strongly affected by climate changes.

Multiphase (unsaturated) porous media are also encountered in several geo-infrastructures, including road, railway and flood embankments, dams, and tunnels where mechanical and hydraulic response (stability, deformation, hydraulic conductivity) is controlled by the interaction of the ground with the atmosphere.