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Numerical 3D simulations of seepage and the seepage stability of the right-bank dam of the Dry Flood Control Reservoir in Racibórz

Strzelecki T., Uciechowska-Grakowicz A., Strzelecki M., Sawicki E., Maniecki Ł.

Studia Geotechnica et Mechanica

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2018

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Vol. 40, nr 1

11--20

EN

This article presents the results of numerical simulations of seepage through the body of the dam and the reservoir bed. The purpose of this study was to analyse the seepage stability during a flood as well as the impact on seepage stability of the diaphragm wall and gravel columns, on which the dam body is founded in selected segments. Simulations were conducted for three different locations, and the following 3D models of the dum were prepared: – a model containing the front and right-bank part of the dam, for which no diaphragm wall, gravel columns and drainage ditch were provided for – a model of a segment of the right-bank dam including a diaphragm wall, drainage ditch and gravel columns under the dam (two variants with differing diaphragm wall lengths) – a model of the water dam segment accounting for gravel columns and a drainage ditch, but without a diaphragm wall. In the case of founding on gravel columns, the base was modelled as an anisotropic medium in terms of seepage properties, macroscopically equivalent to the actual soil medium. The numerical model utilises the finite element method. The geometry of the dam and geological substrate was defined in the GIS tools in the form of a 3D model of the terrain and geology of the substrate.

2

Analysis of the foundation slab settlement of the “Africa Pavilion” facility in Wrocław

Sawicki E., Strzelecki T.

Studia Geotechnica et Mechanica

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2015

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Vol. 37, nr 4

47--55

EN

This article presents the results of numerical calculations of soil consolidation underneath the “Africa Pavilion” structure in Wrocław Zoo, Poland. To determine the deformations of the baseplate of the “Africa Pavilion” and deformations of the subsoil, Biot’s consolidation theory for two-phase medium was applied. The calculations were carried out using the professional program FlexPDE v.6, which is based on the Finite Element Method. Numerical calculations performed were used to evaluate the design assumptions allowing for the laying of hydraulic conduits under the slab.

3

Obliczenia numeryczne 3D i analityczne szczelności zamka stalowej ścianki szczelnej

Sawicki E., Wyjadłowski M.

Materiały Budowlane

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2015

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nr 10

78--81

PL

W projektowaniu głębokich wykopów istotne jest oszacowanie wodoprzepuszczalności ich zabezpieczenia. W przypadku ścianki szczelnej zadanie polega na określeniu przepuszczalności zamka profili stalowych. PN-EN 12063 [1] zaleca zdefiniowanie przepuszczalności w zależności od tzw. parametru szczelności (oporu na przeciek) ρz [m/s], na podstawie którego określa się objętość wody mogącej przepływać przez zamek ścianki szczelnej w jednostce czasu. W artykule przedstawiono metodę oszacowania parametru ρz oraz porównano wyniki obliczeń przepływu przez ściankę szczelną, uzyskane metodą analityczną w oparciu o [1], z wynikami numerycznego modelowania 3D (jako model matematyczny, opisujący rozkład wysokości hydraulicznej w badanym obszarze, przyjęto równanie Laplace'a). Metoda analityczna daje poprawne wartości wydatku, gdy wartość współczynnika filtracji materiału wypełniającego zamek jest dużo mniejsza (dwa rzędy wielkości w przeanalizowanym przykładzie) od współczynnika filtracji sąsiadującego ze ścianką gruntu. Jeżeli warunek ten nie jest spełniony, wydatek obliczony analitycznie jest znacznie zawyżony.

EN

The quantification of seepage ground-water flow through construction of an excavation pit has practical relevance for engineers. In the case of sheet pile wall is to determine the permeability of the joints of profiles. Standard PN-EN 12063 recommends that define the permeability depending on the tightness parameter ρz [m/s]. Based on this parameter determines the volume of water likely to flow through the joint per unit of time. In this approach ρz is regarded as a material parameter wall profile defining its permeability. This paper presents a method to estimate a parameter ρz and compared the results of calculations of discharge, conducted an analytical method based on standard PN-EN 12063 with the results of numerical modelling 3D. In numerical calculations, as a mathematical model describing the hydraulic distribution in the studied area was adopted Laplace equation.Analytical method provides the correct discharge when the value of the permeability coefficient of the filler material is much smaller than the permeability of soil adjacent to the wall. If this condition is not met, the analytically calculated discharge is overestimated.

4

Numerical modeling of vertical wells in unsteady groundwater flow conditions

Strzelecki T., Sawicki E., Strzelecki M.

Studia Geotechnica et Mechanica

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2013

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Vol. 35, nr 2

83--96

EN

This article presents the results of numerical calculations of drainage of a large engineering construction – “Afrykarium” in Wrocław ZOO, Poland, based on a 2D numerical model for seepage flow. In the numerical simulations the real (natural) hydrogeological conditions, water-courses, surface reservoirs and time dependent seepage flow (during drainage) are taken into account. The aim of numerical calculations was to determine quantities (draining time, number of wells, spacing and arrangement of wells, flows for every well, and hydraulic head map) necessary to design an effective drainage system of construction site. The mathematical model adopted to illustrate and predict groundwater depression during pumping was the Boussinesq equation for unsteady 2D flow.

5

Determination of permeability coefficient of saturated clay based on linear segment of settlement curve

Sawicki E., Stróżyk J.

Studia Geotechnica et Mechanica

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2009

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Vol. 31, nr 4

73-84

EN

In this article, the conception of determination of permeability coefficient k based on linear segment of the settlement curve in a compression test is presented. By observing the evolution of the settlement curve of a soil, it is possible to find in its initial part a linear relation between the settlement and time. For clays, the time interval ranges from about 45 sec to a few minutes, as measured from the moment a load has been imposed. The linear character of the graph means that rheological effects are absent and that settlement velocity is constant and equal to percolation velocity. Thus, it may be supposed that within this time interval the permeability coefficient is approximately constant, too. Hence, the value of k calculated on the basis of this linear part of the settlement curve should be reliable. In this paper, the values of permeability coefficient k for clay, obtained in triaxial apparatus were compared with those obtained in oedometer test (based on the linear segment of the settlement curve). The results obtained appear to be promising. Nevertheless, since the number of tests carried out so far is rather small, it is necessary to perform more experiments to verify our conception.

6

One-dimensional consolidation of poroelastic medium with rheological skeleton

Sawicki E.

Studia Geotechnica et Mechanica

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2007

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Vol. 29, nr 3-4

81-88

EN

In this paper, the author presents the results of numerical investigations of poroelastic medium behaviour (consisting of a skeleton and the fluid flowing through the voids in this skeleton), called Biot's body. It is assumed that the stress-strain state does not reach the failure limits of the body. The starting point for these considerations is the phenomenon of one-dimensional consolidation of such a medium described by the fundamental poroelastic Siot's equation and completed by the Biot's-Darcy flow equation. Additionally in this description the rheological properties of the skeleton of Biots body are modelled by linear viscoelastic Zener's body (standard body).

PL

Przedstawiono wyniki badań numerycznych dotyczących zachowania się ośrodka porosprężystego (składającego się ze szkieletu i cieczy wypelniającej pory tego szkicletu), zwanego cialem Biota, w zakresie stanu naprężcnia, w którym nie występuj c jeszcze utrata wytrzymałości ciała. Punktem wyjścia rozważań jest zjawisko konsolidacji takiego ośrodka opisane równaniem porosprężystości Biota, uzupełnionym równaniem przepływu Biota-Darcy'ego. W opisie uwzględniono cechy reologiczne szkieletu ciała Biota, zakładając, że odpowiadają one zachowaniu modelu liniowo lepkosprężystego Zen era (standardowego). Zalożono bowiem, żc podczas procesu konsolidacji ruch cząstek stałych może odbywać się po kontakcie: ciało stałe-ciało stałe bądź po warstewce wody związanej na powierzchni ciała stałego. Otrzymujemy tu zatcm połączenie dwóch niezależnych procesów: i) konsolidacji związanej z zagęszczani cm ośrodka, które jest spowodowane odpływem filtracyjnym wody swobodnej, oraz ii) procesu pelzania rozumianego jako ruch fazy stałej ośrodka, któremu przeciwstawia się opór lepki wynikający z założenia, że przemieszczające się cząstki gruntu "ślizgają się" po warstewcc wody związanej na powierzchni tych cząstek.

7

Coriolis effects during fluid flow through rotating granular porous media

Sawicki E., Geindreau C., Auriault J.

Studia Geotechnica et Mechanica

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2005

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Vol. 27, nr 1-2

143-154

EN

Recently, the filtration law of an incompressible viscous Newtonian fluid flowing through a rigid non-inertial porous medium (e.g. a soil sample placed in a centrifuge basket) which takes into account the Criolis effects was developed by using an upscaling technique [2], [3], [7]. The structure of the law obtained is similar to that of the Darcy's law but the permeability tensor depends on the angular velocity w of the porous matrix, i.e. on the Ekman number Ek. It satisfies the Hall-Onsager's relation and is a non-symmetric tensor. The present study aims at quantifying more precisely the Coriolis effects in a porous medium. For this purpose we performed some 3D numerical simulations for the flow through rotating periodic array of spheres. Our numerical results clearly show the influence of the Coriolis effects on the permeability at large Ekman number e Ť Ek-1 Ť 1 and Ekman number O(l). These results are analyzed according to the geometrical properties of the packings of spheres: soild volume fraction, arrangement and size. Under particular conditions, we finally show that in the first approximation the flow through rotating granular media can be described by a modified Darcy's law including a "macroscopic Coriolis force" which brakes and deviates the flow.