Study of ice content and hydro-mechanical behaviour of frozen soils

• Main Author: Mao, Yanxin
• Other Authors: Gens, A. (Antonio), Romero Morales, Enrique, Universitat Politècnica de Catalunya. Departament d'Enginyeria Civil i Ambiental
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universitat Politècnica de Catalunya 2019
• Subjects: Unsaturated frozen soil; Ice content; Thermal conductivity; Electrical resistivity tomography; THM coupling; Suelo congelado parcialmente saturado; Contenido de hielo; Permitividad dieléctrica relativa; Conductividad térmica; Acoplamiento THM; Àrees temàtiques de la UPC::Enginyeria civil; 55; 624; Hielo; Ice; permafrost
• Online Access: http://hdl.handle.net/10803/667039

Aplicat embargament des de la data de defensa fins el dia de publicació. The hydro-mechanical behaviour of soils during freezing and thawing is a coupled multi-physics process that has important practical applications. To cite but a few examples, on artificial ground freezing –to provide structural support and exclude the groundwater from underground constructions–, on seasonal variations of permafrost soils and their consequences on infrastructures, on geocomposite capillary barriers used to reduce frost heave in soils, and on engineered barriers subjected to freezing and thawing processes. Despite this importance, ice content and its migration process, as well as the coupled hydro-mechanical behaviour have not been extensively studied in partially saturated frozen soils. In these soils, ice formation increases the number of phases and the complexity of the experimental studies. In this thesis, the unfrozen liquid saturation and the hydro-mechanical behaviour of two frozen soils (Barcelona clayey silt and fine sand) have been investigated at different initial degrees of saturation. A series of experimental setups have been designed and built to perform the tests (oedometer cell installed in a freezing/thawing chamber to control the temperature up to -15°C; setup for freezing cylindrical samples in an electrical resistivity tomography ERT cell with 16 lateral electrodes). Different methods have been considered and several models proposed in the thesis to indirectly determine the unfrozen liquid saturation of compacted soils at different temperatures, porosities and initial degrees of saturation. The methods rely on measurements during transient freezing of the bulk electrical conductivity EC, relative dielectric permittivity, and thermal conductivity. In the case of EC tests, the unfrozen liquid saturation results have been interpreted with a modified Archie’s law and compared to the electrical conductivity of the pore liquid. The soil freezing retention curve (unfrozen liquid saturation vs temperature) has ...