Untersuchung und Berechnung der Frosthebungen für die speziellen Randbedingungen einer Baugrundvereisung
Zusammenfassung der Projektergebnisse
Ground freezing and the resulting heave-induced damage are mainly known from road construction in cold regions. However, they can also occur during artificial ground freezing (AGF). The boundary conditions resulting from AGF differ in important aspects from that in road construction, for example, concerning the decisive freezing direction, which runs towards the ground surface during ground freezing. This and other influences on frost heave during AGF are investigated in this research project using a newly designed experimental device. In this regard, it is apparent that the heave due to the formation of the final ice lens in the thermal steady-state significantly exceeds the frost heave in the thermal transient state and, thus, it is decisive in the process of AGF. The outlined results show that the unfrozen area, which provides a flow path to the ice lens, has a major influence on ice lens growth. A shorter flow path leads to an increase in the pressure gradient and, therefore, an increase in the pore-water velocity towards the ice lens. This result is supported here by the water pressure tests. In contrast, no significant influence of different temperature gradients on ice lens formation could be observed in the steady-state phase. A comparison of the freezing directions of BF and TF shows that, especially with short flow paths, the frost heave of the BF experiments exceeds those of the TF. This could be attributed to the effect of gravity and the longitudinal crack formation during freezing. In particular, the hydraulic conductivity increases due to the initiation of the vertical cracks so that an improved water supply is provided. In the numerical simulation of soil freezing and the related instances, a thermo-hydro-mechanical model that augments the macroscopic theory of porous media (TPM) with the phase-field modeling (PFM) for simulating the freezing process in a fluid-saturated porous medium is presented. The water-saturated soil is described within a continuum mechanical framework as a biphase porous material, consisting of an elastic solid (soil skeleton), and pore-fluid (porewater/ice). In this context, thermodynamically-consistent constitutive relationships and phasefield evolution obtained based on satisfying the entropy inequality are utilized. A special feature of the current work lies in presenting a unified phase-field kinematic framework for treating the ice and water phases, considering that both phases refer to the same pore fluid. Moreover, the PFM ensures a smooth transition for the different thermo-mechanical properties during the phase-change process. The mathematical description of the coupled porous-media phase-field problem results in six PDEs. The numerical solution of these equations is carried out using a monolithic scheme within the FE framework. The numerical solutions of the proposed TPM-PFM approach together with the qualitative comparisons with experimental results showed the capability of the proposed model to efficiently capture the coupled processes of temperature field development in space and time, the phase-change process, and the volumetric expansion due to ice formation during freezing, and the formation of ice lenses together with solid stiffness degradation. Important issues and open questions are still to be answered in future works. These include providing a more realistic description of the soil freezing phenomenon by extending the model toward unsaturated porous media, modeling the ice lens formation and the vertical cracks based on the energetic phase-field diffusive fracture approach, and considering large deformations to accurately capture the occurring frost heave.
Projektbezogene Publikationen (Auswahl)
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Investigation of Frost Heave Considering the Boundary Conditions of Artificial Ground Freezing. Transportation Soil Engineering in Cold Regions, St. Petersburg, Russia, May 2019
Niggemann, K.
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Thermo-hydro-mechanical modeling of soil freezing using a coupled phasefield-porous media approach. Sustainable Industrial Processing Summit & Exhibition, 23-27 October 2019.
Markert, B.
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A unified water/ice kinematics approach for phase-field thermo-hydro-mechanical modeling of frost action in porous media. Computer Methods in Applied Mechanics and Engineering, 372, 113358.
Sweidan, Abdel Hassan; Heider, Yousef & Markert, Bernd
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Investigation of Frost Heave Considering the Boundary Conditions of Artificial Ground Freezing. Lecture Notes in Civil Engineering, 273-283. Springer Singapore.
Niggemann, Katharina
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Cryosuction-induced fracturing in multiphase porous materials: Numerical modeling and experimental validation. GAMM 2021 (Virtual Congress). 15-19 March 2021.
Heider, Y.
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Cryosuction‐induced fracturing in multiphase porous materials: Numerical modeling and experimental validation. PAMM, 21(1).
Heider, Yousef; Sweidan, Abdel Hassan & Markert, Bernd
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Experimental study and numerical modeling of the thermo-hydro-mechanical processes in soil freezing with different frost penetration directions. Acta Geotechnica, 17(1), 231-255.
Sweidan, A. H.; Niggemann, K.; Heider, Y.; Ziegler, M. & Markert, B.
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Liquid freezing in porous media: porous media-phase-field modeling and comparison with experimental data. 14th WCCM & ECCOMAS Virtual Congress, 2021
Sweidan, A.H
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Unsaturated porous media freezing: numerical modeling and validation based on experimental data. InterPore2021 Online Conference, 31 May- 4 June 2021.
Sweidan, A.H.
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From freezing-induced to injection-induced non-isothermal saturated porous media fracture. 8th European Congress on Computational Methods in Applied Sciences and Engineering. CIMNE.
Heider, Y.
