Modelling the freezing and thawing behaviour of saturated soils

This thesis presents an investigation of the thermo / hydro / mechanical behaviour of saturated soils with cryogenic suction effects. The flow relationships accommodate a number of mechanisms: i) heat transfer by conduction, convection, and latent heat transfer and ii) moisture transfer in the liquid phase due to pressure head, elevation head, and thermal gradients. The mechanical behaviour of the soil is modelled by an elasto-plastic work hardening modified Cam- Clay constitutive model. A numerical solution for the theoretical formulation is presented. Standard finite element methods are used for spatial discretisation and finite difference methods are used for temporal discretisation. Verification of the model is achieved by means of programme of tests to check the following cryogenic components i) coupled thermo-hydraulic response, ii) deformation behaviour of the fully coupled thermo-hydro-mechanical model, iii) transient coupled liquid flow and deformation behaviour, and iv) latent heat of fusion. Validation focused on the impact of the cryogenic related processes included within the proposed theoretical formulation. In particular the development of ice lenses and the movement of moisture under cryogenic suction were investigated. The performance of the proposed model with respect to a number of variables was subsequently explored in order to determine their effect on the magnitude and growth of ice lenses in a freezing soil. The model was then applied to a large scale freezing experiment, namely a fully coupled thermo / hydro / mechanical simulation. The simulated results show a good correlation with the experimental results by predicting the patterns and trends of experimentally observed behaviour and the cryogenic processes that occur during the freezing and thawing of frost susceptible soils. It was therefore concluded that the proposed model is capable of providing a good representation of the fully coupled THM behaviour of saturated soils with cryogenic effects.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Indicative Status Assessment, Biodiversity Conservation, and Protected Areas Within the Sava River Basin

The aim of this chapter is to provide the overview of the water status, state of the biological diversity, and protected areas along the Sava River as well as to underline the necessity of identification and implementation of effective conservation measures. The chapter is based on historical data on environment and recent investigation on macroinvertebrate communities (2011–2012). Ecological status of water bodies within the Sava River basin ranges from high to poor, while the ecological status of the majority of water bodies is assessed as moderate, which indicates the necessity of design and implementation of relevant mitigation measures. The assessment of water quality and ecological status of the river Sava based on the macroinvertebrates community, alongside with the use of several standard biological methods and regional biotic index BNBI indicates a high correlation of the obtained results. BNBI has proven to be a method reliable enough for both the assessment of water quality and the assessment of ecological status of large rivers. Based on the results of water status assessment, the Sava River could be divided into three zones. The best water quality was recorded within the Slovenian stretch of the river, being within the limits of betamesosaprobic zone, while the ecological status was assessed as a good one. The middle part of the Sava River, stretching mainly through Croatia and Bosnia and Herzegovina, has a somewhat worse water quality, approaching the limit of betamesosaprobic zone, while the ecological status in this part of the flow was also determined as a “good” one. The lower parts of the Sava River flow through Serbia are by all indicators more heavily polluted; the water quality is on the border between beta- and alfamesosaprobic zones, while the ecological status is between “good” and “moderate.” The biodiversity of the Sava River may be considered significant, when compared to similar watercourses of Central Europe and Balkan Peninsula. The work contains a more detailed analysis of the biodiversity of aquatic macroinvertebrates and fish of the main flow of the Sava River. Based on the condition of biodiversity of these groups, the river’s ecosystem is divided into three “macrohabitats.” The first macrohabitat includes the upper rhithron parts of the river through Slovenia, with a significant diversity of stenovalent groups of macroinvertebrates (larvae EPT) and salmonid species of fish (brown trout, grayling, and huchen trout). The second macrohabitat includes the parts of the flow through Croatia and Bosnia and Herzegovina with significant diversity of invertebrates from the groups Odonata, Mollusca, Hirudinea, and Chironomidae and fish from the families of Cyprinidae, Percidae, and Gobiidae. The highest number of protected species of fish has been registered in this section. The third “macrohabitat” includes the lower part of the potamon of the Sava River and mostly flows through Serbia wherein this part of the flow represents the most important habitat of the globally endangered and fishing-wise important sturgeon species of sterlet (Acipenser ruthenus) in this river. It is characterized by a decreased biodiversity of macroinvertebrates in the main flow of the river and a significant diversity in the flood zones. In the biodiversity of fish, the highest number of allochthonous species appears. In this section, the diversity of fish in flood zones especially as the habitat of endangered species such as Umbra krameri, Misgurnus fossilis, and Carassius carassius is also important. Research has shown that in order to perform a successful conservation of large river biodiversity, the ecosystem must be observed as a complex consisting of the main flow of the river, flood zone, and its tributaries.Milačić R, Ščančar J, Paunović M, editors. The Sava River. Berlin, Heidelberg: Springer-Verlag; 2015. p. 453-500