Tymoteusz Zydroń, Andrzej T. Gruchot
Uniwersytet Rolniczy, Kraków

Coal combustion in the heat and power plants causes producing of smoke-box ash, which is generally called fly ash (furnance ash) and ash-slag, which is the result of mixing ash and slag during hydro transport to the landfill. These materials, despite many ways of usage, are still deposited, being a threat to the natural environment. Therefore in order to limit the negative influence of this waste on the environment there are attempts to use them in different fields of industry, for example to produce building materials, hydraulic binding agents, concrete additions or in earthworks for building embankments. However, furnance waste is characterized by a significant diversity of physical and mechanical properties, depending on the coal type, combustion technology, way of transport and depositing, therefore it requires individual evaluation of its geotechnical parameters. Usage of these materials for earthworks means obtaining a proper stability of the construction or its low deformability as a result of loading. Stability of earth constructions depends mainly on the material’s shear strength. The topic of the tests was shear strength of ash-slag from Pleszów landfill of “Kraków” Power Plant in Cracow. The tests were carried out in order to determine the influence of moisture content and compaction on values of angle of internal friction and cohesion. These tests were carried out on samples at the moisture content from the range (0.6–1.2)wopt and the compaction indexes of IS = 0.90, 0.94, 0.97 and 1.00. Based on obtained results it was stated that the unsaturated ash-slag from “Kraków” Power Plant landfill is characterized by high shear strength. Values of angle of internal friction obtained from tests in shear box apparatus were from 31.6 to 38.8°, whereas values of cohesion were from 12.5 to 35.3 kPa. While analyzing tests results it was stated that the increase in ash-slag moisture content influences the decrease in strength parameters of this material, although the changes are not significant. While analyzing tests results it was stated that in case of this type of materials obtained values of cohesion can be debatable. Hence to describe the strength of the ash-slag a simplified model was used. It was assumed that this material when saturated has a zero cohesion, whereas values of cohesion obtained from testes are the result of forces of suction pressure, which depend on the material’s moisture content. The results of theoretical calculations of shear strength gave relatively good compatibility with the direct tests results. Stability calculations integrated with infiltration calculations showed a significant influence of soils’ permeability on slopes equilibrium condition. Analysis results show that typical slopes inclination of 1:1.5 does not guarantee stability of the embankment in case of forced and drowned infiltration. Whereas not allowing the saturation of the mixture significantly improves slope stability. Obtained results show that in order to determine the usability of this material, apart from shear strength parameters, permeability should also be taken into consideration. Stability calculations results prove that to make a decision about usability of this type of material for earthworks it is necessary to determine their geotechnical parameters each time.

Słowa kluczowe
wytrzymałość na ścinanie, popioło-żużle, stateczność zboczy

The Effect of Changes in the Thermal Stratification Time on the Eutrophication Processes in Lakes

Key words
shear strength, ash-slag, slope stability

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