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Analizy bezpieczeństwa konstrukcji budowlanych ulegających degradacji na podłożach górniczych. Część 2. Obliczenia numeryczne

Fedorowicz Lidia, Fedorowicz Jan

Builder

2021

R.25, nr 8

16--21

Wobec założeń upraszczających stosowanych w tradycyjnych metodach oceny bezpieczeństwa konstrukcji na podłożach ulegających deformacjom górniczym wielokrotnie podejmowano próby pełniejszego sformułowania rozważanego zagadnienia brzegowego. Uzyskany rozwój w tej dziedzinie jest wynikiem badań nad reologią zjawiska deformacji poeksploatacyjnych oraz prac dotyczących rozbudowy modeli opisujących zachowanie deformującego się podłoża gruntowego oraz współpracującej z nim budowli. W artykule przedstawiono współczesne tendencje rozwoju numerycznego modelowania zagadnień brzegowych budowla-podłoże górnicze z odniesieniem do doświadczeń własnych autorów oraz przeprowadzonych analiz obliczeniowych wykorzystujących w opisie zaawansowane związki konstytutywne. Pokazano, w jaki sposób jakość i dokładność analiz obliczeniowych związana jest z budową geometryczną modelu MES oraz sprzęgnięta z wymogami parametrycznymi stosowanych modeli konstytutywnych.

In view of the simplifying assumptions used in traditional methods of assessing the safety of structures in mining areas, many attempts have been made to formulate the boundary problem under consideration. The development obtained in this field results from research on the rheology of the post-exploitation deformations and works on the models describing the behavior of the deforming subsoil and structures cooperating with it. The article presents contemporary trends in the development of numerical modeling of boundary issues: building-mining subsoil; with reference to the authors' own experiences and the computational analyzes carried out, using advanced constitutive relationships in the description. It shows how the quality and accuracy of computational analyzes is related to the geometric structure of the FEM model and coupled with the parametric requirements of the constitutive models used.

The relationships between aboveground biomass and Voronoi area of coexisting species in an old-field community

Du F., Xu X., Zhang X., Sui Y., Shao M., Hu L., Shan L.

Polish Journal of Ecology

2012

Vol. 60, nr 3

479-489

Voronoi area of coexisting species in a community has an important role in determining their performances as it is related with the available resources around individuals. Biomass formed within certain Voronoi area probably can be a mark of species that characterised resource competition ability of coexisting species in natural community. In this article, we tried to probe the subject in the following three aspects: 1) what is the apparent relationship between individuals' aboveground biomass and their available Voronoi area for species in natural community? 2) what is the possible theoretic relationship between them? 3) additionally, whether there are any possible indices that can be elicited from species' occupied Voronoi area to reflect species' competitive ability. Using individual-based investigation of aboveground biomass and their corresponding positions, Voronoi area of all individuals of coexisting species in an old field community were computed. The growth of an individual could be regard as a process to compete for resources that is limited by the available area or volume encompassed by the neighborhood individuals. We extended logistic growth model to describe the relationship between Voronoi area and aboveground biomass of coexisting species by relating limiting rhizospheral resource with the Voronoi area around an individual. Theoretically, the individuals aboveground biomass is also controlled by factor-ceiling effects of Voronoi area. So the extended model was fitted with boundary analysis method. And also, their linear relationship was fitted. Under the prediction that competive ability is one of the main driving factors of community succession, two parameters as the Voronoi area of coexisting species and the Voronoi area per unit of aboveground biomass were used to check whether they can designate species' competitive abilities and competitive hierarchies. This was presented by fitting the two parameters with the successional niche positions that was represented by the ordination values along abandonment ages of old field communities in the local area. The results showed that: 1) For most species, the linear regression demonstrated that Voronoi area of an individual that occupied larger Voronoi area tended to have greater aboveground biomass. The nonlinear regression of showed that the relationship might depend upon species' growth characteristics, like shade tolerance and root proliferation. Generally, the relationship could be better fitted by the extended logistic growth model using boundary analysis method than by the linear regression, except for some shade-preferring or clone species. If factor-ceiling effects were considered, at the highest, about 48% of the variation of aboveground biomass could be interpreted by Voronoi area. For some other species with light preference or clone proliferation, the determination coefficient was around zero. 2) Species. averaged Voronoi area had significant and positive Kendall's tau-b and Spearman correlations with successional niches, and species' per-unit aboveground biomass positions of Voronoi area has significantly negative rank correlation with successional niche positions. These indicate that both of them can reflect species' competitive ability and hierarchy to some extent.