Ústav geotechniky

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Experimental study on time dependent behaviour of coarse aggregate concrete mixture for 3D construction printing
(Elsevier, 2023-04-20) Vespalec, Arnošt; Podroužek, Jan; Boštík, Jiří; Miča, Lumír; Koutný, Daniel
This experimental study analyses coarse aggregate-containing and coarse aggregate-free materials from the perspective of additive manufacturing. The primary objective is to identify, through a series of experiments, the fundamental equations that characterise material behaviour at early ages in order to formulate a digital material model. During the research, a previously unreported phenomenon, namely the contradictory development of Young's modulus and cohesion, was observed. In addition, the sensitivity of buildability to changes in material properties was discussed and demonstrated with a motivating example using a spatiotemporal simulation of 3Dprinted concrete.
Optimization of Load-transfer Functions for a Large-diameter Pile in Multi-layered Geological Conditions via a Stochastic Search Algorithm
(Budapest University of Technology and Economics, 2024-10-09) Chalmovský, Juraj
The paper presents the combination of the load transfer method (computational model) and the genetic algorithm (optimization model) for the automated inverse analysis of instrumented pile load tests. The output of this process are the input parameters governing the shape of the load-transfer functions and thus the prediction accuracy when the load-transfer method is used as a design tool for deep foundations. The optimization problem is converted into an unconstrained task by applying the static penalty approach. Two types of measurements are considered in a newly proposed objective function: the load-displacement curve monitored in a pile head and the axial force profiles along a pile derived from strain gauges. Firstly, the local sensitivity analysis via the Design of Experiments is carried out to identify the parameters of the genetic algorithm which significantly influences the rate of convergence during the optimization process. Subsequently, a fully automated inverse analysis of the loading test of the large-diameter bored pile in multilayered geological conditions is presented. The simultaneous combination of two instrumentation sources leads to a stable unique solution with a sufficient match between the prediction and measurements despite a larger number of unknown - optimized variables.
Energy Potential of the Bratislava Neogene
(SCIENDO, 2024-12-27) Slavkov, Juraj; Tomajková, Dana; Brček, Martin; Miča, Lumír
The thermal conductivity of materials is characteristic extensively applied across various contemporary domains, ranging from civil engineering to agriculture. The capacity of a material to conduct heat underscores its significance primarily within civil engineering, particularly in energy-related applications. Notably, in the design of energy geostructures, the thermal conductivity of the soil assumes paramount importance. The principle of energy geostructures is to extract geothermal energy, where the base soil works as a heat source. As the thermal conductivity of the ground increases, the amount of extracted energy increases. It can be concluded that the exact determination of the thermal conductivity of the ground has a significant impact on the design of energy geostructures. This article is dedicated to the first detailed measurements of the thermal conductivity of the Bratislava Neogene in five selected localities on samples from depths of 7.1 m to 14.4 m.
The load-transfer method as a tool for determining the load-displacement curve of piles
(CZECH TECHNICAL UNIV PRAGUE, 2024-09-08) Chalmovský, Juraj; Račanský, Václav; Koudela, Pavel; Zdražil, Karel
The paper presents two applications (software packages) in which the load-transfer method is used for axially loaded Kelly drilled bored piles and displacement ductile iron piles. In the first, the ultimate friction is related to the effective stress via the so-called beta method. The beta method is refined into three stages to cover the variety of soils typical of Central Europe. For the driven piles, a different approach is presented in which the ultimate shaft friction is related to the reference hammering time. The recorded hammering time profile is fed directly into the software based on the load-transfer method. Analyses of five loading tests are presented proving that the load transfer method in combination with the beta method or the recorded hammering time profile is able to compute the load-displacement curve of both replacement and displacement piles with a reasonable accuracy in various geological conditions.
Settlement Analysis of the Nivy Tower in Bratislava by the Finite Element Method
(Faculty of Civil Engineering of The Slovak University of Technology, 2024-10-04) Chalmovský, Juraj; Červenka, Jan; Dobrovolský, Ján; Račanský, Václav
A settlement analysis of a new high-rise building, the Nivy Tower, in Bratislava, Slovakia, is presented in this paper. A 3D finite element model was prepared. A non-linear elasto-plastic material model with double hardening and increased stiffness in a small-to-very-small strain range was adopted for the Tertiary (Neogene) subsoils. Due to the lack of an appropriate in-situ test, the results from a 1D compression test were used for the calibration of the soil input parameters. However, the results from these tests, especially in the primary loading, are often biased due to the effects of soil disturbance during the preparation of the sample. Therefore, a different procedure has been proposed, in which the stiffness parameters were obtained from unloading-reloading branches of 1D compression tests. It could be concluded that the predicted and measured settlements are in a reasonable match for all the points measured. The computed distributions of the vertical displacements and those measured by sliding micrometres show greater differences from a depth of twenty meters beneath the foundation slab.

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