A Passive House (PH) system is not only an opportunity but also a necessity for the further development of sustainable eco-buildings. Construction of the foundation in energy-efficient houses is the key to maintaining low energy losses. The appropriate selection of building materials requires considering the thermal conditions of the environment, including its location and the zero isotherms in the ground. The main objective of this work is to analyze the possibilities of designing foundations for PHs in Poland, according to the current methodological data. In order to realize the basic aims, the work was divided into the following materials and methods: (I) literature review; (II) database of PH in Central Europe; (III) method of depth of ground freezing determination; (IV) selection of the joint of slab-on-ground foundation and external wall to analysis; (V) description and validation of the heat-transfer model. The result of the research work is: (i) analysis of the foundation under the conditions of freezing of the ground in Poland; (ii) description and validation of the heat-transfer model. The research has revealed that in the Polish climate zone, the most efficient solution for passive buildings is to build them on a foundation slab. The foundation of a building below the latest specified ground frost depths in Poland is inefficient in terms of, for example, thermal insulation, economics, and the idea of PH.

The European standards, developed extensively over last 30 years, are driven by the need for continuous evolution and their Authors’ pursuit of better EU-wide quality in civil engineering – combining safety, economy, and sustainable development. The adoption of theory of reliability as the basis for design has played a major role in shaping current geotechnical practice. However, it requires from practitioners a greater understanding of underlying uncertainties. Furthermore, a number of alternative approaches, not generally used in structural design, are also allowed, as some situations in geotechnical engineering require an individual approach. Moreover, the current trends in geoengineering increase the importance of risk assessment and management. The paper presents general philosophy guiding the geotechnical design and pointing to some of the ideas introduced by Eurocode 7 and its requirements, in relation to preexisting practice of geotechnical design in civil engineering.

Increasingly complex design systems require an individual approach when determining the necessary design parameters. As soils are characterized by strong strain-dependent nonlinearity, test methods used to characterize the subsoil should be carefully selected, in terms of their “sensitivity” as well as suitability for the analyzed type of problem. When direct measurements are not available, while design calculation models require specific parameters, indirect parameter estimation may be used. This approach requires calibration and validation of empirical correlations, based on well documented database of tests and case studies. One of the parameters often used, when analyzing soil-structure interaction problems, is the shear stiffness of the soil and its strain-dependent degradation. The aim of the article is to present the procedure for description and evaluation of soil stiffness based on field tests (CPTU, DMT and SDMT) and a large number of reference curves obtained from laboratory tests (TRX) for selected soil types. On the basis of the given algorithm, it is possible to obtain a stiffness module G0 value at any level of deformation, based on in-situ tests.

Accurate frost depth prediction is an important aspect in different engineering designs such as for pavements, buildings, bridge foundations, and utility lines. This paper presents a probabilistic method of assessment of the depth of soil freezing. Annual (winter) maxima of the position of the zero centigrade temperature measured in the soil were approximated by Gumbel probability distribution. Its parameters were estimated using maximum likelihood method. The results received on the basis of data from 36 meteorological stations in Poland and 50 years of observations, as characteristic values with 50-year return period, reflect the influence of the climatic conditions on the freezing depth. On the other hand, the soil structure and its conditions also play an important role in freezing. Nowadays they may be taken into account using correction coefficients. It is concluded that this method is more precise than a method using the air freezing index because through the use of direct measurements it takes into account additional factors affecting the actual depth of freezing. The obtained results are not the same as those given in the older Polish Standard which was based on the simplified and limited data. The results confirm the impact of climate change on ground freezing depth.

This article presents the results of seismic shear wave velocity (V_S) measurements using the CSWS/SAWS (Continuous Surface Wave System/Spectral Analysis of Surface Waves) and SDMT (seismic flat dilatometer) methods, as well as BET (Bender Elements Test), on an experimental test site (and samples taken from it). The test site, a geologically relatively uniform alluvial sand formation area, was carefully chosen and checked for uniformity by means of drillings and soundings. The research aimed to determine how results from indirect, non-invasive surface geophysical tests (SASW and CSWS) correspond with those from SDMT penetration tests as well as the BET laboratory seismic method, and how some methodological aspects can influence them. Different wave sources and frequency were examined as the main factors for interpretation. The influence of other examined factors is also discussed.

The requirements for field research for Polish conditions demand proper dependences. Dependences based on more than 30 localizations for different genetic types of soils were derived for the area of Poland. Direct results from CPT, DMT and profiles from boreholes have been collected at the test sites for individual localization. For interpretation of results, dependences and diagrams of CPTU versus DMT were created. Correlations on the background of results from literature for different types of soils for numerous research areas were collected, with established dependences for Polish grounds conditions. Additionally some recommendations for the interpretation of the results from CPTU and DMT tests for analysed soils have been proposed.