Analysis of factors influencing levee safety using the DEMATEL method

River embankments are the basic and the oldest measures of protecting areas potentially subjected to flooding, and at the same time pose a serious threat to their environment in the event of damage or failure. The technical condition of the levees and its regular evaluation is a key element of their safety. A general assessment of the technical condition of a levee is the result of many interacting factors and parameters that depend on each other to a varying degree. Therefore, it is necessary to consider the cause-and-effect links between the interrelationships of numerous parameters and sensors of significant impact. In this article the decision-making trial and evaluation laboratory (DEMATEL) method was applied to develop a cause-and-effect model for factors impacting the condition and safety of levees. Effective factors impacting the technical condition of a levee were identified; relationships between these factors were determined; a cause-and-effect model was developed based on identified factors; factors were categorized based on the dependence scale and influential indicators of each factors used in the DEMATEL method. The obtained results demonstrate that three following factors: hydrological factor, type and condition of soils in levee body and condition of levee areas (inter-levee and landside) play the most important role for levee safety. The results of this study can support traditional assessments of hydrotechnical structure or assist entities managing levees.

SEASONAL CONDITIONS OF PHYTO-FOULING OF A COASTAL PROTECTION HYDROTECHNICAL STRUCTURE (KRUGLAYA BAY, BLACK SEA)

The species composition, ecological and taxonomic structure, quantitative characteristics and variability of phyto-fouling of the coastal hydrotechnical structure (Kruglaya Bay, Sevastopol) in spring, summer and autumn were studied. The taxonomic composition of fouling is represented by 45 species of 29 genera, 19 families, 12 orders, 4 classes of the divisions Chlorophyta, Ochrophyta and Rhodophyta. The taxonomic leaders of the community are Rhodophyta, Cladophorales, Ceramiales, Ulvaceae, Cladophoraceae, Ceramiaceae, Ulva, Cladophora, Ceramium, ecological — marine, leading, annual and oligosaprobic species. The fouling is dominated by species with a high and medium frequency of occurrence. Most of the proportions of taxa and ecological groups are most resistant. The taxonomic diversity of the entire phyto-growth, its Rhodophyta, constant flora nucleus, minor species and some ecogroups, the occurrence of species, phytomass, the degree of community discreteness and the qualitative composition of its production dominants and subdominants are subject to seasonal fluctuations. Each season, the variability of the species composition corresponds to the norm for biological objects, the degree of variability of the phytomass is higher.

Effect of Variation of Temperature Field on the Process of Thermal Consolidation of Tailings Pond “Zelazny Most”

The following study presents numerical calculations for establishing an impact of temperature changes on the process of distortion of bi–phase medium. The Biot consolidation equations with Kelvin–Voigt rheological skeleton were used for that purpose. The process was exemplified by thermal consolidation of post floatation dump “–elazny Most”. We analyzed the behavior of the landfill under the action of its own weight, forces of floating filtration and temperature gradient. Values of certain effective parameters of model were obtained during laboratory tests on material obtained from the landfill. The remaining data for mediums with similar characteristics were taken from literature. The results obtained from the stress state in the landfill allow the magnitude of plasticity potential to be specified based on known strength criteria. Change in the value sign of the plasticity potential clearly testifies to the emergence of an area of plasticity of material from landfill, however, this does not indicate the loss of stability of this hydrotechnical structure.

Application of theory of semi-Markov processes to determining distribution of probabilistic process of marine accidents resulting from collision of ships

ABSTRACT In this paper is presented possible application of the theory of semi-Markov processes to elaborating an eight-state model of the process of occurrence of serviceability state and unserviceability states of sea-going ships making critical manoeuvres during their entering and leaving the ports. In the analysis it was taken into account that sea-going ships are in service for a very long time t (t → ∞). The model was elaborated to determine the probability (P0) of correct execution of critical manoeuvres during ship’s entering and leaving the port as well as the probabilities Pj(j = 1, 2, 3, …, 7) of incorrect execution of critical manoeuvres by a ship, that leads to marine accidents. It was assumed that such accidents result from: ship’s grounding on port approaching fairway, collision with a ship on port approching fairway, collision with a pierhead during passing through port entrance, collision with a hydrotechnical structure during ship’s passing through port channels, collision with a port quay during coming alongside it and collision with a ship already moored to the quay. The probability (P0) was assumed a measure of safe execution of a critical manoeuvre. The probability characterizes possibility of avoiding any collision during ship’s entering and leaving the port. The probability Pa = 1 - P0 was assumed a measure of occurrence of a collsion and - consequently - marine accident. The probability Pa was interpreted as a sum of the probabilities Pj(j = 1, 2, 3, …, 7) of occurrence of all the selected events. In summing up the paper, attention was drawn to its merits which - in opinion of this author - are crucial for research on real process of accidents during entering the port and leaving it by sea-going ship in difficult navigation conditions.