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 requirement for implementing local measurements at small strains is well known. Without this type of measurement, it is not possible to accurately identify the soil stiffness characteristics over the entire stiffness degradation curve. The paper presents the results of the use of new sensor based on miniature magnetic encoders for axial and radial deformation measurements in triaxial soil test. Presented results include two types of measurement techniques for radial direction and one for axial deformation.
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.
Typical ranges of variability of basic soil parameters are relatively well known. Such knowledge is important to aid engineers in the selection of characteristic values for design or as a basis for conducting sensitivity analyses for more complex soil-structure interaction problems. However, for application of advanced non-linear constitutive models, which often are defined by model-specific parameters, such variability is rarely known. To improve parameter estimation, as well as to provide a basis for the choice of realistic variability range, a database of high quality laboratory tests can be used. The paper presents the results of preliminary assessment of variability of selected Hardening Soils model parameters for overconsolidated glacial tills and clays from Poland, based on a local database of triaxial test results.
The impact of low-range temperature variation on the residual shear strength parameters has been investigated. For this purpose, a standard ring shear apparatus has been subjected to low-cost modifications and equipped with thermoelectric temperature control system constructed in-house. This allowed to conduct a series of tests for clay samples at temperatures of 5°C and 20°C, which is a typical range of variation for thermo-active structures during heat extraction. In order to distinguish the impact of temperature from the natural variability of the soil samples, additional temperature changes during shearing were performed, after residual strength had been reached. The obtained results revealed an observable impact of the temperature change on the residual shear strength of tested clay; however, the variance has been close to the resolution of the measurement sensor and within the range comparable to the natural variability of fine-grained soils. Therefore, low-range temperature changes can be considered as negligible in regard to the residual shear strength parameters.
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