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Of the various types of road structures, bridges are the most exposed to icing; the problem of icing is widely addressed through salting, which reduces the lifespan of the bridge. One promising solution to avoid the use of salt is the seasonal storage of solar heat energy captured directly through the asphalt layer; however, this solution can only be achieved cost effectively if a necessary geostructure is used as a heat exchanger. In this study, such an approach is studied for a bridge crossing a canal, and the geotechnical and energy-related challenges of such a solution are discussed. Bridge piers and abutments are located on piles, which are used as heat exchangers. Depending on local conditions, seasonal storage and natural thermal reload are two possible solutions for the operation of such a system. In particular, the presence of underground water flow is thought to be a significant factor in such a design and is considered here. This study aims to determine the geotechnical and energy design parameters through thermo-hydro-mechanical simulations. A threedimensional finite-element model analysis is necessary given the distance between bridge piles. Various underground water flow scenarios are studied. The capture of energy and de-icing requirements is based on the few existing structures that use other means of energy exchange with the ground. The results indicate that the use of heatexchanger piles for de-icing bridges can only be considered at specific sites; however, the efficiency of the solution at those sites is high. Possible foundation and structure stability problems are also considered, such as vertical displacements due to the dual use of the foundation piles.

h i g h l i g h t s• A semi-analytical solution is proposed to assess CO 2 injection in deformable medium.• Good agreement is found between the proposed solution and the finite element method.• Geomechanical interactions between a caprock and adjacent regions are examined.• The surface uplift measured at In Salah can be reproduced by the proposed solution.a r t i c l e i n f o b s t r a c tThis study focuses on the derivation of a semi-analytical approach for the evaluation of surface uplift and caprock deflection induced by underground injection of CO 2 . The adopted methodology includes the development of a mathematical model that incorporates the deformable behaviour of the storage reservoir and the flow of two immiscible fluids (CO 2 and brine) within the aquifer while the surface rock or the caprock layer is modelled as a thin plate. Governing equations are solved for the axisymmetric flexural deflection due to a constant rate of CO 2 injection. Both developed solutions are applied to a representative CO 2 storage case solved numerically by the finite element method, and good agreement between results is observed. When benchmarking to the In Salah surface uplift, the developed semi-analytical approach can capture a high rate of surface uplift caused by the pressure build-up during the early stage of CO 2 injection. The required calculation time is very short compared to a classical finite element approach. This method can be employed as a design tool for the analysis of uncertainty in parameters such as the injection rate, porosity, rock properties and geological structures. This semi-analytical approach also provides an efficient means of estimating the influence of high injection rates of CO 2 on surface uplift.

A deep geological repository involving a multi-barrier system constitutes one of the most promising options to isolate high-level radioactive waste from the human environment. In order to certify the efficiency of waste isolation, it is essential to understand the behaviour of the confining geomaterials under a variety of environmental conditions. The efficiency of an Engineered Barrier System (EBS) is largely based on the complex behaviour of bentonite. To contribute to a better understanding of the processes involved in the EBS, a case study for sensitivity analysis has been defined and is studied using a thermo-hydro-mechanical (THM) finite element approach including a consistent thermoplastic constitutive model for unsaturated soils. The model also features a coupled THM approach of the water retention curve. Various couplings were studied separately and in combination in order to determine the significance of each. The same principle is applied to physical phenomena such as vapour diffusion. This study clearly highlights the effects that need to be taken into consideration for a correct assessment of EBS behaviour.

Rainfall-induced landslides in volcanic ashes represent a major natural hazard in many regions around the world. Owing to their loose structure, volcanic ash slopes are prone to rainfall-induced landslides. The paper presents a continuum modelling approach for the analysis of wetting-induced instability phenomena at the onset of failure in loose volcanic ash slopes. A numerical simulation of a landslide-prone volcanic slope in Costa Rica is carried out with a two-dimensional hydro-mechanical finite-element slope model. A constitutive model based on the effective stress concept extended to partially saturated conditions is used to reproduce the volcanic ash hydro-mechanical behaviour. The model parameters were calibrated through a previous extensive laboratory testing campaign. Simulation results allow the behaviour of the slope during rainfall infiltration to be anticipated and the development of the failure mechanism to be analysed. Results of the coupled numerical model demonstrate the important role of wetting and drying cycles, slope geometry and bedrock on the timely evolution of matric suctions and wetting-induced deformations. Moreover, it is observed that the pore collapse upon wetting enhances the development of a localised shear failure mechanism in unsaturated conditions.