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Pozycja Historia i perspektywy rozwoju Katedry Geotechniki i Budowli Inżynierskich Politechniki Łódzkiej(Wydawnictwo Politechniki Łódzkiej, 2011) Lefik, Marek; Sztromajer, ZofiaW artykule przedstawiono krótko ponad pięćdziesięcioletnią historię Katedry Geotechniki i Budowli Inżynierskich Politechniki Łódzkiej. Omówiono podstawowe tematy działalności naukowej, scharakteryzowano zespoły i osoby, które te badania prowadzą. Opisano prace habilitacyjne zakończone i przygotowywane w Katedrze. Artykuł kończą prognozy i wnioski dotyczące rozwoju Katedry.Pozycja Hybrid, finite element-artificial neural network model for composite materials.(Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej, 2004) Lefik, MarekAn application of Artificial Neural Networks for a definition of the effective constitutive law for a composite is described in the paper. First, a classical homogenisation procedure is directly interpreted with a use of this numerical tool. Next, a self-learning Finite Element code (FE with ANN inside) is used in the case when the effective constitutive law is deduced from a numerical experiment (substituting here a purely phenomenological approach). The new contribution to the classical self-learning procedure consists of its adaptation to a case of a non-monotonic loading (non-to-one load-deformation curve). This new ability of the method is principally due to the incremental form of the constitutive equation and the respective scheme of the neural network structure. Also an organisation of a constitutive data-base containing learning patterns is suitably modified. It is shown by examples that the training process is very quick. The error of this method is smaller, comparing to other schemes of data acquisition.Pozycja Main properties of sands hydrophobized by alkoxysilane emulsions(2014) Wojciechowski, Marek; Baryła, Patrycja; Lefik, MarekThe results of laboratory tests and geotechnical view on sands hydrophobized by alkoxysilane emulsions are presented. For the soils subjected to this process, very low permeability and no capillary elevation was observed. Laboratory tests also indicate that other physical and mechanical properties of hydrophobized sands remain nearly untouched, i.e., the considered hydrophobisation process does not reduce the strength of soils. Properly composed alkoxysilane emulsions can also solidify in pores to produce a stabilizing silicate binder. The filtration barriers in ground and soil stabilization are thus considered as possible applications of the hydrophobized soils. The process of treatment of granular soils with alkoxysilanes is neutral for the environment and the cost of implementation of the method is relatively low.Pozycja Two Scales, Hybrid Model for Soils, Involving Artificial Neural Network and Finite Element Procedure(2014) Krasiński, Marcin; Lefik, MarekA hybrid ANN-FE solution is presented as a result of two level analysis of soils: a level of a laboratory sample and a level of engineering geotechnical problem. Engineering properties of soils (sands) are represented directly in the form of ANN (this is in contrast with our former paper where ANN approximated constitutive relationships). Initially the ANN is trained with Duncan formula (Duncan and Chang [2]), then it is re-trained (calibrated) with some available experimental data, specific for the soil considered. The obtained approximation of the constitutive parameters is used directly in finite element method at the level of a single element at the scale of the laboratory sample to check the correct representation of the laboratory test. Then, the finite element that was successfully tested at the level of laboratory sample is used at the macro level to solve engineering problems involving the soil for which it was calibrated.