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    Wyświetlanie 1-6 z 6
    Tytuł:
    Wybrane zagadnienia dotyczące wyznaczania wartości charakterystycznych w geotechnice
    On some issues of characteristic values evaluations in geotechnics
    Autorzy:
    Pula, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/40160.pdf
    Data publikacji:
    2014
    Wydawca:
    Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
    Tematy:
    geotechnika
    badania geotechniczne
    grunty
    wlasciwosci
    wspolczynnik zmiennosci
    teoria pol losowych
    skala fluktuacji
    funkcja redukcji wariancji
    norma PN-EN 1997-1:2008
    geotechnics
    geotechnical research
    ground
    soil property
    variability coefficient
    random field theory
    fluctuation scale
    variance reduction function
    PN-EN 1997-1:2008 standard
    Opis:
    W pracy zaprezentowano różne sposoby określania wartości charakterystycznych właściwości gruntu w kontekście postanowień obowiązującego Eurokodu 7. Po przedstawieniu najprostszych propozycji podano przykład porównujący różne metody. Następnie podano podstawowe fakty dotyczące opisu właściwości podłoża za pomocą pól losowych oraz koncepcję uśrednień przestrzennych. Zreferowano też metodę Schneidera, uwzględniającą w sposób jawny przestrzenną zmienność właściwości gruntu przy określaniu wartości charakterystycznych. Propozycję tę zilustrowano przykładem związanym z mechanizmem Prandtla, a wyniki odniesiono do rezultatów wynikających z uśrednienia właściwości wzdłuż linii poślizgu w tym mechanizmie. Rezultaty wykazują, że zastosowanie teorii pól losowych wraz z propozycją Schneidera daje rezultaty zgodne z wymaganiami Eurokodu 7. Zwrócono uwagę na istotną rolę podejścia probabilistycznego w wyznaczaniu parametrów do projektowania geotechnicznego w kontekście oceny bezpieczeństwa. Niniejszy artykuł jest rozszerzoną wersją prezentacji przedstawionej na konferencji ProGeotech (SGGW, Warszawa 12-13.09.2013).
    The paper presents various possibilities of evaluating characteristic values of soil properties in the context of Eurocode 7 recommendations. Some simplest approaches have been illustrated by computing and comparing resulting of characteristic values. Next the very basic concepts of random fields and spatial averaging were introduced. Consecutively, as application, the Schneider method has been demonstrated and applied to bearing capacity problem incorporating Prandtl's mechanism. The obtained results were compared with evaluation based on spatial averaging along slip lines (in Prandtl's mechanism). It appears that random field approach in conjunction with Schneider's method gave satisfactory results considering Eurocode 7 requirements. It has been pointed out that probabilistic approach in selecting parameters for geotechnical design plays a vital role in safety evaluation.
    Źródło:
    Acta Scientiarum Polonorum. Architectura; 2014, 13, 1
    1644-0633
    Pojawia się w:
    Acta Scientiarum Polonorum. Architectura
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Technical note: Comparison between two methods for estimating the vertical scale of fluctuation for modeling random geotechnical problems
    Autorzy:
    Pieczyńska-Kozłowska, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/178384.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    scale of fluctuation
    spatial variability
    Opis:
    The design process in geotechnical engineering requires the most accurate mapping of soil. The difficulty lies in the spatial variability of soil parameters, which has been a site of investigation of many researches for many years. This study analyses the soilmodeling problem by suggesting two effective methods of acquiring information for modeling that consists of variability from cone penetration test (CPT). The first method has been used in geotechnical engineering, but the second one has not been associated with geotechnics so far. Both methods are applied to a case study in which the parameters of changes are estimated. The knowledge of the variability of parameters allows in a long term more effective estimation, for example, bearing capacity probability of failure.
    Źródło:
    Studia Geotechnica et Mechanica; 2015, 37, 4; 95-103
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bearing capacity of eccentrically loaded strip footing on spatially variable cohesive soil
    Autorzy:
    Dobrzański, Jędrzej
    Kawa, Marek
    Powiązania:
    https://bibliotekanauki.pl/articles/2041290.pdf
    Data publikacji:
    2021
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    random field
    scale of fluctuation
    eccentric load
    cohesive soil
    probabilistic analysis
    Opis:
    The study considers the bearing capacity of eccentrically loaded strip footing on spatially variable, purely cohesive soil. The problem is solved using the random finite element method. The anisotropic random field of cohesion is generated using the Fourier series method, and individual problems within performed Monte Carlo simulations (MCSs) are solved using the Abaqus finite element code. The analysis includes eight different variants of the fluctuation scales and six values of load eccentricity. For each of these 48 cases, 1000 MCSs are performed and the probabilistic characteristics of the obtained values are calculated. The results of the analysis indicate that the mean value of the bearing capacity decreases linearly with eccentricity, which is consistent with Meyerhof's theory. However, the decrease in standard deviation and increase in the coefficient of variation of the bearing capacity observed are non-linear, which is particularly evident for small eccentricities. For one chosen variant of fluctuation scales, a reliability analysis investigating the influence of eccentricity on reliability index is performed. The results of the analysis conducted show that the value of the reliability index can be significantly influenced even by small eccentricities. This indicates the need to consider at least random eccentricities in future studies regarding probabilistic modelling of foundation bearing capacity.
    Źródło:
    Studia Geotechnica et Mechanica; 2021, 43, 4; 425-437
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An iterative algorithm for random upper bound kinematical analysis
    Autorzy:
    Chwała, Marcin
    Powiązania:
    https://bibliotekanauki.pl/articles/2073758.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    random bearing capacity
    shallow foundation
    scale of fluctuation
    iterative algorithm
    upper bound
    spatial variability
    Opis:
    A new approach for stochastic upper bound kinematical analyses is described. The study proposes an iterative algorithm that uses the Vanmarcke spatial averaging and kinematical failure mechanisms. The iterative procedure ensures the consistency between failure geometry and covariance matrix, which influences the quality of the results. The proposed algorithm can be applied to bearing capacity evaluation or slope stability problems. The iterative algorithm is used in the study to analyse the three-dimensional undrained bearing capacity of shallow foundations and the bearing capacity of the foundation for two-layered soil, in both cases, the soil strength spatial variability is included. Moreover, the obtained results are compared with those provided by the algorithm, based on the constant covariance matrix. The study shows that both approaches provide similar results for a variety of foundation shapes and scale of fluctuation values. Therefore, the simplified algorithm can be used for purposes that require high computational efficiency and for practical applications. The achieved efficiency using a constant covariance matrix for one realisation of a three-dimensional bearing capacity problem that includes the soil strength spatial variability results in about 0.5 seconds for a standard notebook. The numerical example presented in the study indicates the importance of the iterative algorithm for further development of the failure mechanism application in probabilistic analyses. Moreover, because the iterative algorithm is based on the upper bound theorem, it could be utilised as a reference for other methods for spatially variable soil.
    Źródło:
    Studia Geotechnica et Mechanica; 2022, 44, 1; 13--25
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On determining the undrained bearing capacity coefficients of variation for foundations embedded on spatially variable soil
    Autorzy:
    Chwała, Marcin
    Powiązania:
    https://bibliotekanauki.pl/articles/178626.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    spatial averaging
    random field
    random bearing capacity
    fluctuation scale
    failure mechanism
    Opis:
    This paper presents an efficient method and its usage for the three-dimensional random bearing capacity evaluation for square and rectangular footings. One of the objectives of the study is to deliver graphs that can be used to easily estimate the approximated values of coefficients of variations of undrained bearing capacity. The numerical calculations were based on the proposed method that connects three-dimensional failure mechanism, simulated annealing optimization scheme and spatial averaging. The random field is used for describing the spatial variability of undrained shear strength. The proposed approach is in accordance with a constant covariance matrix concept, that results in a highly efficient tool for estimating the probabilistic characteristics of bearing capacity. As a result, numerous three-dimensional simulations were performed to create the graphs. The considered covariance matrix is a result of Vanmarcke’s spatial averaging discretization of a random field in the dissipation regions to the single random variables. The matrix describes mutual correlation between each dissipation region (or between those random variables). However, in the presented approach, the matrix was obtained for the expected value of undrained shear strength and keep constant during Monte Carlo simulations. The graphs were established in dimensionless coordinates that vary in the observable in practice ranges of parameters (i.e., values of fluctuation scales, foundation sizes and shapes). Examples of usage were given in the study to illustrate the application possibility of the graphs. Moreover, the comparison with the approach that uses individually determined covariance matrix is shown.
    Źródło:
    Studia Geotechnica et Mechanica; 2020, 42, 2; 125-136
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Estimation of spatial variability of lignite mine dumping ground soil properties using CPTu results
    Autorzy:
    Bagińska, I.
    Kawa, M.
    Janecki, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/178889.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    Random Field Theory
    fluctuation scale
    CPTu testing
    dumping ground soil
    Opis:
    The paper deals with application of CPTu test results for the probabilistic modeling of dumping grounds. The statistical measures use results from 42 CPT test points located in the lignite mine dumping ground from the region of Central Europe. Both the tip resistance qc as well as local friction fs are tested. Based on the mean values and standard deviations of measured quantities the specific zones in the dumping site profile are distinguished. For three main zones standard deviations of linearly de-trended functions, distributions of normalized de-trended values for qc and fs are examined. Also the vertical scales of fluctuation for both measured quantities are estimated. The obtained result shows that lignite mine dumping site can be successfully described with the Random Field Theory. Additional use of fs values introduces supplementary statistical information.
    Źródło:
    Studia Geotechnica et Mechanica; 2016, 38, 1; 3-13
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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