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1
Content available remote Elastic properties of self-compacting concrete modified with nanoparticles: Multiscale approach
Stefaniuk D., Niewiadomski P., Musial M., Lydzba D.
Archives of Civil and Mechanical Engineering
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2019
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Vol. 19, no. 4
1150--1162
EN
Advances in cementitious composites and nanotechnologies have led to the development of self-compacting concrete (SCC) modified with nanoparticles. SCC with Al2O3 nanoparticles was used in this study. In addition, a reference sample of SCC without an addition of nanoparticles was investigated. First, the micro-mechanical properties of each phase of the composites were examined using the statistical nanoindentation techniques and deconvo-lution. Then, the interfacial transition zone (ITZ) was investigated using line indentation and X-ray microCT. The results indicated that the ITZ played no significant role in the compo-sites. Subsequently, modified Mori–Tanaka and self-consistent homogenization schemes, accounting for random variability of constituent properties, were applied to evaluate the overall elastic properties of the composites. Then, macroscale laboratory (uniaxial compres-sion) tests were carried out to verify the adopted approach. The results of the micro- and macroscale tests showed that the proposed laboratory investigation procedure and homog-enization approach were proper. Finally, the modified Mori–Tanaka scheme was used to verify the influence of material composition on the effective elastic modulus of SCC with Al2O3 nanoparticles.
2
Content available Influence of bedding and backfill soil type on deformation of buried sewage pipeline
Grosel S., Pachnicz M., Różański A., Sobótka M., Stefaniuk D.
Studia Geotechnica et Mechanica
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2018
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Vol. 40, nr 4
313--320
EN
In the paper, the influence of different types of bedding and backfill soil surrounding underground sewage duct on its deformation was analysed. Impact of increased soil lateral pressure was examined by considering the construction of an embankment nearby the underground pipeline. Numerical computations of three different variants of bedding and backfill soil surrounding the pipe were carried out. Displacements and deformation of the pipe were calculated using the finite element method with adoption of elastic-perfectly plastic constitutive model of soil. Subsequent stages of the construction were taken into account. Shear strength reduction method was applied to evaluate the factor of safety of the entire system. Finally, the results and conclusions were depicted.
3
Content available O zagrożeniach związanych z projektowaniem kolumn DSM w gruntach organicznych
Kanty P., Rybak J., Stefaniuk D.
Nowoczesne Budownictwo Inżynieryjne
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2017
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Nr 2
70--75
PL
W artykule zaprezentowano aktualne uwarunkowania dotyczące projektowania wzmocnień i posadowień w technologii Deep Soil Mixing (DSM), wyniki badań laboratoryjnych prób cementogruntu uformowanych w warunkach laboratoryjnych z zaczynu cementowego i torfu oraz konsekwencje stosowania tworzyw o niskich parametrach wytrzymałościowych i odkształceniowych. Badania na próbkach sześciennych pozwoliły na wyznaczenie wytrzymałości na ściskanie i rozciąganie oraz modułu odkształcenia. Wyniki późniejszych analiz numerycznych uzyskano z wykorzystaniem programu metody elementów skończonych Z_Soil i danych z badań laboratoryjnych. Wykonane obliczenia stanowią poważne ostrzeżenie i praktyczną podstawę do wnioskowania o ograniczonej możliwości skutecznej modyfikacji gruntów organicznych z wykorzystaniem technologii DSM.
EN
The paper outlines the current aspects of designing reinforcements and foundations using Deep Soil Mixing (DSM) technology, the outcomes of laboratory test of soil cement samples obtained in laboratory conditions from cement grout and peat, and the consequences of using materials with low strength parameters and deformation strength. In the tests conducted on cubic samples, the compressive and tensile strength, and the deformation module were determined. The results of subsequent numerical analyses were obtained with the use of finite elements method Z_Soil and data from laboratory tests. The results of the calculations bring a serious warning and provide practical ground to conclude that the capability to efficiently modify organic soil using DSM is limited.
4
Analiza konstrukcji gruntowo-powłokowej poddanej działaniu wody
Łydżba D., Różański A., Sobótka M., Stefaniuk D., Chudy G., Wróblewski T.
Mosty
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2017
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nr 1
20--28
PL
Celem analiz numerycznych jest ocena możliwości użytkowania mostu gruntowo-powłokowego zlokalizowanego w czaszy suchego zbiornika przeciwpowodziowego. Zamodelowano fazę budowy oraz użytkowania obiektu przy rożnych stanach piętrzenia: zbiornik suchy, maksymalne piętrzenie, opadanie wody w zbiorniku. Analizowano zmiany sił wewnętrznych i naprężenia w powłoce wywołane wskutek kilku cykli ruchomego, quasi-statycznego obciążenia taborem samochodowym.
EN
The planned construction of a dry reservoir Roztoki Bystrzyckie is a part of the flood control program in the Kłodzko Valley. The project includes, i.a., the construction of a new section of road with a soil-steel bridge over the Nowinka stream. The road crosses the reservoir basin, which can be filled with water during flood. The aim of the numerical analysis presented in the paper is the assessment of the possibility of using the structure under varying water conditions. The structure under consideration is a three-span soil-steel bridge made of corrugated steel sheets. 2D calculations are carried out assuming elastic-plastic behavior of soil and varying pore pressure distributions. First, the construction stage is modelled. This includes laying and compaction of the backfill. Then, the bridge in operation is investigated under three different water conditions: normal use (dry reservoir), maximum water level (flood) and lowering of the water level in the reservoir. The main part of the analysis concerns mainly the variation of both internal forces and stress in the shell due to quasi-static live load.
5
Content available remote Zastosowanie mikrotomografii komputerowej do oceny ewolucji sieci spękań w materiałach kruchych
Łydżba D., Pachnicz M., Rajczakowska M., Różański A., Sobótka M., Stefaniuk D.
Materiały Budowlane
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2017
|
nr 6
48--49
PL
W artykule przedstawiono analizę wyników badania w mikrotomografie komputerowym sieci spękań w próbkach skalnych, poddanych testom jednoosiowego ściskania. Próbki były skanowane w mikrotomografie komputerowym przed testem, następnie po obciążeniu siłą o wartości 40 – 50% siły niszczącej, a także po osiągnięciu granicy makrodylatancji (lub granicy wytrzymałości). Analiza uzyskanych trójwymiarowych obrazów skanowania pozwoliła opisać w sposób ilościowy morfologię sieci spękań: porowatość, rozkłady przestrzenne szerokości spękań i krętości, a także wskaźnik SMI (ang. structure model index). Znajomość wymienionych wielkości jest przydatna przy określaniu parametrów przepuszczalności badanego materiału.
EN
The paper presents the analysis of crack network development induced in rock samples, subjected to uniaxial compression. The samples were scanned using micro-computer tomography after three stages of load: before loading, after application of a force equal to 40–50% of ultimate limit and, finally, after reaching microdilatancy threshold (or ultimate limit force). The analysis of acquired 3D images at every loading stage included fracture network segmentation and determination of chosen quantities describing its morphology: porosity (fraction of void space), spatial distribution of fracture aperture, tortuosity as well as structure model index (SMI). The parameters can be used to determine permeability parameters of cracked material.
6
Content available remote Wykorzystanie nanoindentacji w sposób sekwencyjny do oceny właściwości strukturalnych materiałów mikroniejednorodnych
Łydżba D., Pachnicz M., Rajczakowska M., Różański A., Sobótka M., Stefaniuk D.
Materiały Budowlane
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2017
|
nr 6
50--51
PL
W artykule przedstawiono wyniki testów nanoindentacji przeprowadzone na próbce skalnej. Zastosowano sekwencyjną indentację, tj. autorski program obciążenia próbki. Pozwoliło to obserwować zmienność modułu sprężystości w zależności od skali obserwacji. Wydzielono dwie skale obserwacji, tj. mikro i mezo. Najmniejsza stosowana siła indentacji 0,5 mN prowadzi do odpowiedzi mechanicznej składników tworzących szkielet. Wyniki uzyskane w przypadku najwyższej siły – 500 mN, reprezentują parametr efektywny dla tzw. zastępczej mikrostruktury jednorodnej.
EN
The paper presents results of nanoindentation tests carried out for intact rock specimen. The sequential nanoindentation is used and the novel loading schedule, for prescribed tip position, is applied. It enables us to identify the mechanical morphology at different observation scales. Two scales were identified, i.e., micro- and meso-scale. The lowest value of indentation force, 0.5 mN, provides the mechanical response of the constituents forming the skeleton. The results obtained for the highest value of indentation force, 500 mN, represent the effective property for the so-called „equivalent” homogeneous microstructure.
7
Content available remote Ocena stateczności zapory ziemnej zbiornika przeciwpowodziowego Roztoki Bystrzyckie
Łydżba D., Batog A., Sobótka M., Pachnicz M., Różański A., Stefaniuk D., Wróblewski T., Chudy G.
Geoinżynieria : drogi, mosty, tunele
|
2017
|
nr 3
34--38
PL
Metodyka oceny stateczności skarp i zboczy budowli hydrotechnicznych podlega, w myśl aktualnych przepisów, dwóm różnym rozporządzeniom. Z jednej strony obowiązują zasady projektowania geotechnicznego, podane w Eurokodzie 7, z drugiej (równolegle) zapisy rozporządzenia ws. warunków technicznych, jakim powinny odpowiadać budowle hydrotechniczne i ich usytuowanie. W artykule podjęto próbę udzielenia odpowiedzi na pytanie, w jakim stopniu wybór pomiędzy wymienionymi podejściami wpływa na uzyskiwane wyniki analizy stateczności zapory suchego zbiornika przeciwpowodziowego Roztoki Bystrzyckie.
EN
The methodology of the scarps and slopes stability assessment of the hydrotechnical structures can be considered in relation to two different regulations: Eurocode 7 and Polish geotechnical design regulations. The authors attempt to define what kind of regulations should be followed, concerning the hydrotechnical structures and their localizations. In the article there is presented an answer to the question: how the choice of the regulations affects the stability assessment of the earth fill dam of the storage reservoir Roztoki Bystrzyckie.
8
Content available Mechanical behavior of soil-steel structure subjected to live loads and different water conditions
Łydżba D., Różański A., Sobótka M., Stefaniuk D., Chudy G., Wróblewski T.
Archiwum Instytutu Inżynierii Lądowej
|
2017
|
Nr 23
163--174
EN
The paper describes the analysis of a three-span soil-steel bridge along the road section crossing a dry anti-flood reservoir. The structure can be occasionally filled with water. The authors investigate internal forces and stresses in the shells due to live loads at different water conditions. Finite element simulations are carried out assuming elastic-plastic behavior of soil, elastic shell and nonlinear (frictional) contact zone. The analysis takes into account soil load history. In particular, the construction and operation of the bridge under quasi-static live loads is considered. The construction stage includes laying and compaction of the backfill. Then, the bridge in operation is investigated at three different water conditions: normal use (dry reservoir), maximum water level (flood) and lowering of the water level in the reservoir. The results show that during the flood the maximum stress in the shell significantly increases. Moreover, some of non-linear effects, typical in such structures, e.g. hysteretic effect, become more evident in comparison to normal use of the bridge.
9
Content available Recovery of microstructure properties: random variability of soil solid thermal conductivity
Stefaniuk D., Różański A., Łydżba D.
Studia Geotechnica et Mechanica
|
2016
|
Vol. 38, nr 1
99--107
EN
In this work, the complex microstructure of the soil solid, at the microscale, is modeled by prescribing the spatial variability of thermal conductivity coefficient to distinct soil separates. We postulate that the variation of thermal conductivity coefficient of each soil separate can be characterized by some probability density functions: fCl(λ), fSi(λ), fSa(λ), for clay, silt and sand separates, respectively. The main goal of the work is to recover/identify these functions with the use of back analysis based on both computational micromechanics and simulated annealing approaches. In other words, the following inverse problem is solved: given the measured overall thermal conductivities of composite soil find the probability density function f(λ) for each soil separate. For that purpose, measured thermal conductivities of 32 soils (of various fabric compositions) at saturation are used. Recovered functions f(λ) are then applied to the computational micromechanics approach; predicted conductivities are in a good agreement with laboratory results.
10
Content available The effectiveness of earth structures rein-forcement on mining areas: numerical analysis
Pachnicz M., Rajczakowska M., Stefaniuk D.
Mining Science
|
2016
|
Vol. 23
203--214
EN
This paper presents a numerical analysis of a Multi-layer soil structure improved with the use of geosynthetics. Numerical calculations using the finite element method (FEM) in ZSoil program were performed to determine the effectiveness of the applied reinforcement. In the solution of the problem, different boundary conditions were modeled to analyze the influence of several technologies on the construction of a rail road embankment, subjected to the effect of mining works. In the analysis, the applied loads correspond to the II category of the mining area. Mainly, the different load conditions reflect the intensity of the subsidence of the ground surface due to mining. The effectiveness of the soil reinforcement was determined using the comparison of the numerical calculations of displacements and strains for different scenarios. The reinforcement conditions were always contrasted among them and against the rail road embankment without any improvement. The displacements were measured at the surface of the rail road embankment. The slope stability of the embankment was measured using the soil shear strength reduction method (SSR). The obtained results show, that applying the appropriate reinforcement to the soil, the load/bearing capacity and the stability of the earth structure located in a zone of mining influence can be improved considerably.
11
Content available Microstructure characterization by means of X-ray micro-CT and nanoindentation measurements
Rajczakowska M., Stefaniuk D., Łydżba D.
Studia Geotechnica et Mechanica
|
2015
|
Vol. 37, nr 1
75--84
EN
The aim of this paper is to present an example of the material microstructure characterization with the use of X-ray micro-CT and nanoindentation measurements. Firstly, the current scope of application of the aforementioned techniques is provided within different fields of science. Then, background of each of the methods is presented. The methodology of X-ray micro-CT is described with the emphasis on the Beer’s law formulation. In addition, the basics of the nanoindentation technique are outlined and major formulas for the hardness and Young’s modulus calculation are given. Finally, example results for a concrete sample are presented. The microstructure of the selected material is firstly characterized in terms of geometry using the results from the microtomograhy measurements, e.g., porosity and attenuation profiles, pore and aggregate size distribution, shape factor of pores, etc. Next, the results of the nanoindentation tests are provided, namely the hardness and Young’s modulus versus the height of the sample. The influence of the number of tests and statistical analysis on the final results is underlined.
12
Content available X-ray microtomography (μCT) as a useful tool for visualization and interpretation of shear strength test results
Stefaniuk D., Tankiewicz M., Stróżyk J.
Studia Geotechnica et Mechanica
|
2014
|
Vol. 36, nr 4
47--55
EN
The paper demonstrates the applicability of X-ray microtomography (μCT) to analysis of the results of shear strength examinations of clayey soils. The method of X-ray three-dimensional imaging offers new possibilities in soil testing. The work focuses on a non-destructive method of evaluation of specimen quality used in shear tests and mechanical behavior of soil. The paper presents the results of examination of 4 selected clayey soils. Specimens prepared for the triaxial test have been scanned using μCT before and after the triaxial compression tests. The shear strength parameters of the soils have been estimated. Changes in soil structure caused by compression and shear failure have been presented as visualizations of the samples tested. This allowed for improved interpretation and evaluation of soil strength parameters and recognition of pre-existing fissures and the exact mode of failure. Basic geometrical parameters have been determined for selected cross-sections of specimens after failure. The test results indicate the utility of the method applied in soil testing.
13
Content available Identification of the carbonation zone in concrete using X-ray microtomography
Łydżba D., Rajczakowska M., Stefaniuk D., Kmita A.
Studia Geotechnica et Mechanica
|
2014
|
Vol. 36, nr 1
47--54
EN
The article presents an application of X-ray microtomography for identification of the carbonation zone in concrete material. A concrete specimen subjected earlier to harsh environmental conditions is investigated. The material is firstly checked with the use of chemical corrosion indicators and then is subjected to microstructural analysis performed with the use of X-ray microtomography. Two different settings of scanning parameters are applied implying the image resolutions of approximately 14 μm per 1 pixel and about 7 μm per 1 pixel, respectively. The results obtained are then compared and analyzed. The depth of the carbonation zone is evaluated based on the attenuation curve. The paper highlights also the significance of the corrosion phenomenon in concrete structures. Details of the deterioration mechanisms in concrete are shortly presented.
14
Content available Efficiency of the needle probe test for evaluation of thermal conductivity of composite materials: two-scale analysis
Łydżba D., Różanski A., Rajczakowska M., Stefaniuk D.
Studia Geotechnica et Mechanica
|
2014
|
Vol. 36, nr 1
55--62
EN
The needle probe test, as a thermal conductivity measurement method, has become very popular in recent years. In the present study, the efficiency of this methodology, for the case of composite materials, is investigated based on the numerical simulations. The material under study is a two-phase composite with periodic microstructure of “matrix-inclusion” type. Two-scale analysis, incorporating micromechanics approach, is performed. First, the effective thermal conductivity of the composite considered is found by the solution of the appropriate boundary value problem stated for the single unit cell. Next, numerical simulations of the needle probe test are carried out. In this case, two different locations of the measuring sensor are considered. It is shown that the “equivalent” conductivity, derived from the probe test, is strongly affected by the location of the sensor. Moreover, comparing the results obtained for different scales, one can notice that the “equivalent” conductivity cannot be interpreted as the effective one for the composites considered. Hence, a crude approximation of the effective property is proposed based on the volume fractions of constituents and the equivalent conductivities derived from different sensor locations.
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