In a reservoir tailwater of the large, lowland Warta River, perch and ruffe coexist in a macrophyte habitat, which develops as a result of low water discharge in the late spring and summer. At the beginning of each year the diet of both percids, when shorter than 100 mm, is dominated by large, benthic Hydropsyche. Later in the year, epiphytic Chironomidae and Simuliidae replace these trichopterans in the perch diet, and benthic Chironomidae replace them in the ruffe diet. Large cladoceran species then become accessory food items for perch. Consequently, the food niche overlap of these two percids during the research period is only marginal.
Omówiono praktyczne aspekty wykonywania pali wierconych. Zwrócono uwagę na czynniki wykluczające zastosowanie danej technologii, pomijane często podczas wyboru właściwej metody palowania na etapie projektowania. Opracowanie dotyczy pali CFA (Continous Flight Auger Piles).
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This paper describe the practical side of forming CFA bored piles. The authors take into consideration factors which preclude using a particular technologies and at the same time which are omitted by engineers while searching a proper method of drilling at the design stage. The study concerns CFA piles (Continous Flight Auger Piles).
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The choice of deep foundation method needs to be preceded by a thorough analysis of the conditions in every engineering project studied. The application of deep foundations construction is usually called for in cases when transferring the load forces from the construction itself to the deeper bearing layers of the ground, if the shallow layers have insufficient capacity. This solution is a result of a number of factors, such as construction requirements and economic conditions. Interfering in deep ground layers carries a load of unknowns risks and threats. Therefore, ignoring the construction issues during the project preliminary stage may lead to serious consequences during the realization of the construction project.
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