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Thermoactive geostructures are considered an economically suitable and environment-friendly solution for heating and cooling buildings. Energy tunnels have gained growing interest in recent years because of the large ground volume involved in heat exchange in comparison to building foundations. Heat exchange is obtained by embedding a circuit of pipes into the precast concrete lining, resulting in a reduction of the initial costs of installation with respect to standard low-enthalpy geothermal solutions. In this paper, thermal activation of the twin tunnels of the II line of Warsaw metro, Poland, is considered with the aim of evaluating the geothermal potential of the line. Thermohydraulic finite-element analyses were performed on a number of representative cross-sections, considering site-specific hydrogeological conditions based on the Engineering Geological Database of the Capital City of Warsaw. Results demonstrate that the thermal activation of the two 1·6 km-long tunnels could exchange up to 5·3 and 5·8 GWh in the heating and cooling seasons, respectively. Furthermore, the influence of the local geological conditions on the exchangeable heat rate was investigated. The results form a basis for a preliminary assessment of the shallow geothermal energy utilisation potential for the design of further extensions of the metro line in Warsaw.

Intensive development of railway infrastructure in Poland is associated with significant support provided for that purpose by the European Union, especially, by investments in the modernization of existing railway lines. Together with the improvement of the infrastructure in less developed countries, an interoperability of rail system at the international level is sought through the technical harmonization, mostly by the introduction of European regulations and technical standards. The paper presents the main requirements associated with the geotechnical aspects of design of railway embankments, mostly relating to their overall stability and maintenance of serviceability. Some aspects of the European standards as well as international, national, and internal regulations, are discusses in the context of challenges encountered by designers. The main geotechnical issues are associated with safety requirements, loading conditions, geometry of railway embankments, as well as the scope of geotechnical investigation necessary to make an informed decision on a final design solution.

This paper presents the current conditions of and perspective on development of the use of shallow geothermal energy as a renewable energy source in highly urbanised areas in Poland, using the Warsaw municipality as an example. The type of geothermal energy source considered in the paper is the thermoactive foundation elements of high-rise buildings and underground structures. The rising demand for new office, commercial and housing spaces in Warsaw fosters the development of new engineering projects, mostly involving deep foundations and structural elements well suited for shallow geothermal energy utilisation. In this study, the preliminary assessment has been made, considering the city-scale impact of the thermoactive foundations. New as well as planned construction areas for new engineering projects in Warsaw were evaluated on the basis of spatial management plans and analysis of local geotechnical and geothermal conditions. Furthermore, the legal issues concerning the use of thermoactive foundations are discussed, considering the current state of the national regulations and the typical construction process.

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Thermoactive piles ensure a dual function: they support mechanically the superstructure and at the same time they are used as heat exchanger elements. In comparison to standard design practice, this requires considering the associated thermal loadings from the operation of the heat exchange system. To assess the thermal effects on the mechanical behaviour, different design assumptions and modelling approaches can be used. Therefore, within the framework of European Cooperation in Science and Technology Action TU1405 ‘Geothermal Applications for Buildings and Infrastructures’, benchmarking of a single geothermal pile has been performed. Hence, both heating and cooling of the pile were considered while different rigidities (representing the upper structure) on the pile head were assumed. The results show that a broad range of design assumptions could be used, which unfortunately lead to noticeable differences. Although the main focus was on the methods and assumptions employed, the exercise also opens questions about the influence of transient effects, thermal strains in the ground, temperature cycles and so on. Owing to the complexity of the topic, some of them were just mentioned, while others were addressed in greater detail. In general, the findings emphasise the need for further practice-oriented guidance to be presented in design guidelines and standards.

The paper presents the summary of five case studies related to structural failures that were caused by the change in groundwater conditions during the existence of the buildings. The failures resulted from excessive differential settlements that were caused either by reactivation of consolidation process, due to change in effective stresses, or a change in water content in the case of expansive soils.

The advantages of establishing databases of soil parameters are recognized within the geotechnical community. Especially, statistical description of soils is necessary tool for establishing probability distribution functions used in reliability based design framework and in standard deterministic approach of limit state design; previous knowledge, comparable experience, and engineering judgement, all play a major role in the selection process of characteristic values of most essential parameters. This is often done in face of limited amount of data from site investigation. The paper presents preliminary database compilation attempt for some parameters of overconsolidated glacial tills and clays from Poland. Due to a rapid growth of infrastructure and cities, analysis of already gathered data is essential for providing engineers with guidance on the variability of soil conditions, which is most noticeable in the case of fine‐grained overconsolidated strata. Focus is given to parameters obtained from triaxial laboratory tests, including small‐strain shear stiffness obtained from Bender Element Test.