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1
Content available Deformations and stability of granular soils: Classical triaxial tests and numerical results from an incremental model
Sławińska-Budzich Justyna, Mierczyński Jacek
Studia Geotechnica et Mechanica
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2020
|
Vol. 42, nr 2
137--150
EN
This article presents a modified incremental model describing pre-failure deformations of granular soils under classical triaxial conditions. The original shape of equations has been proposed by Sawicki and Świdziński [40, 41]. A new form of equations that are consistent with the proposed definitions of deviatoric loading and unloading is suggested. Triaxial tests necessary for calibrating the proposed model have been performed. The modified model is used to simulate the deformations and stability of sand for every pre-failure loading path and makes it possible to describe the behaviour of granular soil under both drained and undrained conditions. A comparison of experimental and numerical results is presented. All investigations were performed in a classical tri-axial apparatus.
2
Content available Basic set of experiments for determination of mechanical properties of sand
Sawicki A., Mierczyński J., Świdziński W.
Bulletin of the Polish Academy of Sciences. Technical Sciences
|
2014
|
Vol. 62, nr 1
129--137
EN
A basic set of experiments for the determination of mechanical properties of sands is described. This includes the determination of basic physical and mechanical properties, as conventionally applied in soil mechanics, as well as some additional experiments, which provide further information on mechanical properties of granular soils. These additional experiments allow for determination of steady state and instability lines, stress-strain relations for isotropic loading and pure shearing, and simple cyclic shearing tests. Unconventional oedometric experiments are also presented. Necessary laboratory equipment is described, which includes a triaxial apparatus equipped with local strain gauges, an oedometer capable of measuring lateral stresses and a simple cyclic shearing apparatus. The above experiments provide additional information on soil’s properties, which is useful in studying the following phenomena: pre-failure deformations of sand including cyclic loading compaction, pore-pressure generation and liquefaction, both static and caused by cyclic loadings, the effect of sand initial anisotropy and various instabilities. An important feature of the experiments described is that they make it possible to determine the initial state of sand, defined as either contractive or dilative. Experimental results for the “Gdynia” model sand are shown.
3
Content available remote Mechanics of seabed liquefaction and resolidification
Sawicki A.
Archives of Mechanics
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2014
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Vol. 66, nr 5
307–-328
EN
The problem of pore water pressure changes in the seabed is considered. Two mechanisms of pore pressure changes are distinguished. The first is caused by external excitations, such as earthquakes, when pore pressure is gradually generated, leading to liquefaction. The second mechanism is caused by water waves, and it leads to cyclic changes in pore water pressure and the mean effective stress. Under certain conditions, when the effective stress path tends to exceed the failure condition, the regrouping of effective stresses takes place, as the soil should accommodate to new conditions. Then, the mechanism of resolidification of the seabed is described. It is concluded that after resolidification, the seabed is in a virgin state, as liquefaction erases the previous history of the seabed structure. A critical discussion of selected existing approaches to the problem of pore-pressure changes and the mechanism of liquefaction is presented in detail, in the form of extensive appendices. Some of these appendices deal with the crucial aspects of the mechanics of liquefaction such as, for example, the drained/undrained conditions.
4
Content available Prędkość wznoszenia kapilarnego w gruntach niespoistych
Wysocka M., Szypcio Z., Tymosiak D.
Budownictwo i Inżynieria Środowiska
|
2013
|
Vol. 4, no. 2
167--172
PL
W pacy przedstawiono wyniki badań kapilarności czynnej i prędkości podciągania kapilarnego w piaskach średnich i pospółkach o różnym stopniu zagęszczenia. Maksymalna wysokość podciągania kapilarnego (kapilarność czynna) jest odwrotnie proporcjonalna do wskaźnika porowatości e i średnicy miarodajnej d10. Prędkości podciągania kapilarnego w gruntach niespoistych są duże w początkowej fazie i szybko maleją wraz z upływem czasu. Dla piasków średnich zagęszczonych stabilizacja wysokości podciągania może następować po kilkudziesięciu lub kilkuset godzinach.
EN
The paper presents test results of capillary raise speed in medium sand or sand and gravel mix at different degree of compaction. The maximum value of capillary raise (active capillarity) is inversely proportional to void ratio (e) and grain diameter (d10). The values of capillary raise speed in granular soils are high in the initial phase and then decrease over time. In medium compacted sands capillary raise may stabilise within more then ten to more then hundred hours (few days).
5
Content available Estimation of Stresses in a Dry Sand Layer Tested on Shaking Table
Sawicki A., Kulczykowski M., Jankowski R.
Archives of Hydro-Engineering and Environmental Mechanics
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2012
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Vol. 59, nr 3-4
101-112
EN
Theoretical analysis of shaking table experiments, simulating earthquake response of a dry sand layer, is presented. The aim of such experiments is to study seismic-induced compaction of soil and resulting settlements. In order to determine the soil compaction, the cyclic stresses and strains should be calculated first. These stresses are caused by the cyclic horizontal acceleration at the base of soil layer, so it is important to determine the stress field as function of the base acceleration. It is particularly important for a proper interpretation of shaking table tests, where the base acceleration is controlled but the stresses are hard to measure, and they can only be deduced. Preliminary experiments have shown that small accelerations do not lead to essential settlements, whilst large accelerations cause some phenomena typical for limit states, including a visible appearance of slip lines. All these problems should be well understood for rational planning of experiments. The analysis of these problems is presented in this paper. First, some heuristic considerations about the dynamics of experimental system are presented. Then, the analysis of boundary conditions, expressed as resultants of respective stresses is shown. A particular form of boundary conditions has been chosen, which satisfies the macroscopic boundary conditions and the equilibrium equations. Then, some considerations are presented in order to obtain statically admissible stress field, which does not exceed the Coulomb-Mohr yield conditions. Such an approach leads to determination of the limit base accelerations, which do not cause the plastic state in soil. It was shown that larger accelerations lead to increase of the lateral stresses, and the respective method, which may replace complex plasticity analyses, is proposed. It is shown that it is the lateral stress coefficient K0 that controls the statically admissible stress field during the shaking table experiments.
6
Content available Deformations and liquefaction of granular soils in plane strain conditions
Sawicki A., Sławińska J.
Archives of Hydro-Engineering and Environmental Mechanics
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2012
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Vol. 59, nr 1-2
13-35
EN
An incremental model is proposed to describe pre-failure behaviour of granular soils in plane strain conditions. The model has been derived from an approach applied in the analysis of triaxial tests. We have applied the methods of tensor algebra to transfer our triaxial results to a 2D case. The model describes the pre-failure deformations of fully drained sands and phenomena associated with undrained response such as static liquefaction. This model has a simple structure in the form of incremental equations. For some simple loading paths, these equations can be integrated analytically. For more complex loading paths a simple numerical algorithms will be sufficient. The model takes into account an initial anisotropy of soil which is ignored in most models. It also takes into account the initial state of soil, defined as rather contractive or dilative, in addition to classical geotechnical division into loose and dense sands. The proposed constitutive equations allow the study of pre-failure instabilities of sand, and some examples are presented. We have also derived analytically the equation for an instability line.
7
Content available remote Osiadania fundamentów bezpośrednich posadowionych na gruntach ziarnistych
Dołżyk K.
Inżynieria Morska i Geotechnika
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2011
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nr 4
248-251
PL
Analiza parametrów odkształceniowych piasków. Metodyka obliczeń osiadania stóp fundamentowych o różnym kształcie. Przykłady porównawcze obliczeń osiadania stóp fundamentowych wraz z komentarzem.
EN
Calculation methodology of settlements of various shape footings. Some calculation examples and discussion.
8
Content available remote Neural identification of compaction characteristics for granular soils
Kłos M., Waszczyszyn Z., Sulewska M.
Computer Assisted Mechanics and Engineering Sciences
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2011
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Vol. 18, no. 4
265-273
9
Content available Stress-strain relations for dry and saturated sands. Part II: Predictions
Sawicki A., Świdziński W.
Journal of Theoretical and Applied Mechanics
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2010
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Vol. 48 nr 2
329-343
EN
In the second part of the paper, the incremental constitutive model, described in details in Part I, was verified against the experimental data obtained from the stress paths different that those used for model calibration. The differential equations defining the model were integrated for various stress paths such as anisotropic consolidation including oedometric conditions, standard triaxial compression, spherical unloading of fully drained soil as well and shearing of water saturated sand in undrained conditions. The behaviour of both initially contractive and dilative soil was considered. Theoretical predictions were compared with the respective experimental data. In all cases examined, the agreement between predictions and experimental data seems to be quite good.
PL
W części II przedstawiono predykcje modelu przyrostowego dla ścieżek naprężenia innych niż te stosowane przy kalibracji. Równania przyrostowe scałkowano dla ścieżek naprężenia i odkształcenia odpowiadających następującym warunkom: anizotropowa konsolidacja, warunki edometryczne, standardowa próba trójosiowa, sferyczne odciążenie przy stałym dewiatorze oraz ścinanie nawodnionego gruntu w warunkach bez odpływu wody z porów. Rozpatrzono reakcję gruntu w początkowym stanie dylatywnym i kontraktywnym. Predykcje teoretyczne porównano z wynikami doświadczeń. Wykazano dobrą zgodność tych predykcji z eksperymentem.
10
Content available Stress-strain relations for dry and saturated sands. Part I: Incremental model
Sawicki A., Świdziński W.
Journal of Theoretical and Applied Mechanics
|
2010
|
Vol. 48 nr 2
309-328
EN
The incremental model describing the pre-failure behaviour of granular soils is proposed. Firstly, the constitutive equations are derived from the extensive set of experimental data, for the triaxial configuration. The following features are included into the model: initial anisotropy, initial state of sand (i.e. either dilative or contractive), instability line. Then, the incremental constitutive equations are generalized to the 3D case, using techniques of tensor algebra. Finally, the model is re-derived for the undrained conditions in order to predict such phenomena as, for example, static liquefaction. The approach presented is an alternative to already classical approaches as the elasto-plasticity or hypoplasticity. The paper consists of two parts. Part I deals with the formulation of the model and its calibration, whereas Part II is devoted to verification of the model against experimental results.
PL
Zaproponowano model przyrostowy opisujący zachowanie się gruntów sypkich przed osiągnięciem stanu granicznego. Równania konstytutywne wyprowadzono bezpośrednio ze związków naprężenie-odkształcenie, otrzymanych z badań trójosiowych. W modelu uwzględniono początkową anizotropię gruntu, jego stan początkowy (dylatywny lub kontraktywny) oraz linię niestabilności. Równania przyrostowe zostały uogólnione na przypadek trójwymiarowy, zgodnie z regułami algebry tensorowej. Model zastosowano do symulacji zachowania się nawodnionego gruntu w warunkach bez odpływu wody z porów, co prowadzi między innymi do zjawiska upłynnienia. Przedstawione podejście jest alternatywą do modeli sprężysto-plastycznych oraz hipoplastycznych. Część I pracy dotyczy sformułowania modelu i jego kalibracji, a w części II przedstawiono predykcje modelu, które porównano z wynikami doświadczeń.
11
Content available Strains in Sand Due to Cyclic Loading in Triaxial Conditions
Sawicki A., Mierczyński J., Świdziński W.
Archives of Hydro-Engineering and Environmental Mechanics
|
2009
|
Vol. 56, nr 1-2
85-98
EN
The experimental results dealing with the cyclic loading of sand samples in triaxial conditions are presented. These results show the development of both the volumetric and deviatoric permanent strains due to a large number of loading cycles. The analysis of experimental data has led to the formulation of semi-empirical constitutive equations, expressed in the incremental form, for these strains as functions of the cyclic shear stress amplitude, number of loading cycles and the initial stress state, around which the cyclic shearing takes place.
12
Content available Pore-Pressure Generation and Liquefaction of Granular Soil Tested in Triaxial Conditions
Mierczyński J., Sawicki A.
Archives of Hydro-Engineering and Environmental Mechanics
|
2009
|
Vol. 56, nr 3-4
139-147
EN
The paper deals with modelling of pore-pressure generation in saturated sand subjected to triaxial cyclic loading in undrained conditions. The model proposed links the pore-pressure generation with the cyclic loading induced compaction of the same sand, but tested in fully drained conditions. The governing equation for the pore-pressure changes is derived from the assumption that no volumetric strain develops in saturated sand in undrained conditions. The numerical solutions are compared with experimental data, for a large number of loading cycles.
13
Content available 3D and 2D Formulations of Incremental Stress-Strain Relations for Granular Soils
Sawicki A.
Archives of Hydro-Engineering and Environmental Mechanics
|
2008
|
Vol. 55, nr 1-2
45-53
EN
3D formulation of incremental relations, describing pre-failure deformations of granular soils, is presented. The starting point are respective equations formulated previously for the axi-symmetrical configuration, as that in the tri-axial apparatus. These relations, proposed for particular configuration, are generalized in the form of tensor equations for the strain increments. Similarly, the loading/unloading criterion and the instability line have been generalized for 3D conditions. A kind of cross-isotropy of granular soil is taken into account. Then, the incremental stress-strain relations for the plane strain state are re-derived from general equations, as such conditions are most often used for simulations of practically important problems. The procedure proposed in this paper is practically oriented, as the soil parameters can be determined just from the tri-axial tests.
14
Badania zagęszczenia gruntów gruboklastycznych metodą geodezyjną
Król P., Sas W.
Prace Naukowe Politechniki Warszawskiej. Inżynieria Środowiska
|
2007
|
z. 54
47-52
PL
W artykule przedstawiono metodę określania stopnia zagęszczenia gruntów gruboziarnistych na podstawie pomiarów osiadań powierzchni, wywołanych dodatkowym przejazdem walca. Badania wykonano dla nasypów uformowanych z narzutu kamiennego i żwirów rzecznych. Otrzymane wyniki porównano z wyznaczonymi tradycyjna metodą dołów próbnych. Porównanie wykazało dużą zgodność rezultatów.
EN
The paper presents the estimation of the relative density (ID) values of the coarse grained materials using measurements of the surface layer settlement caused by an additional passage of the compaction equipment. The tests were conducted for embankments constructed of calcareous rock fill material and alluvial gravel (Fig. 1). The results conducted on tests embankments (Fig. 2 and 3) were used to obtain the relationships for estimation of the ID - values as the function of average surface settlements (Fig. 4). Comparison of the results obtained using simple method proposed here with the results obtained using traditional one showed good agreement (Fig. 5).
15
Badania laboratoryjne i polowe gruntów gruboziarnistych na przykładzie odpadów kopalnianych
Kawalec B., Kawalec J.
Prace Naukowe Politechniki Warszawskiej. Inżynieria Środowiska
|
2007
|
z. 54
37-46
PL
W pracy przedstawiono aparaturę wielkowymiarową stosowaną w krajowych laboratoriach do badań gruntów gruboziarnistych. Omówiono sposób prowadzenia badań nasypów w skali naturalnej. Zaprezentowano wybrane wyniki badań oraz przykłady praktycznych zastosowań w budownictwie ziemnym.
EN
Large scale apparatuses used in Polish laboratories to examine large fraction soils has been presented in the paper. Testing methodology for natural scale embankments has been discussed. Seleeted test results and examples of practical applications in earth and civil engineering are attached as well.
16
Analiza i ocena wpływu składu granulometrycznego i litologicznego oraz kształtu ziarn i stopnia obtoczenia gruntów gruboklastycznych z doliny Dunajca na właściwości mechaniczne
Pisarczyk S., Gałązka T.
Prace Naukowe Politechniki Warszawskiej. Inżynieria Środowiska
|
2007
|
z. 54
59-78
PL
W referacie przedstawiono wyniki badań uziarnienia, składu litologicznego, kształtu i stopnia obtoczenia ziarn gruntów gruboklastycznych (grubych) z różnych złóż z doliny Dunajca. Przeanalizowano również wpływ omawianych parametrów na: zagęszczalność, wytrzymałość na ścinanie i ściśliwość badanych gruntów.
EN
In the article there are shown the results of such tests as: the grain-size distribution, the lithological composition, the grain shape and the stage of rounding of the coarse-grained soils from the different pla­ces of the Dunajec River Basin. There is also discussed the influence of the investigated parameters on the compactibility, the shear strength and the compressibility of the coarse-grained soils.
17
Content available Drained Against Undrained Behaviour of Sand
Sawicki A., Świdziński W.
Archives of Hydro-Engineering and Environmental Mechanics
|
2007
|
Vol. 54, nr 3
207-222
EN
The incremental constitutive equations describing the pre-failure deformations of sand are presented. These equations were calibrated on the basis of extensive experimental data, obtained from investigations performed in a triaxial apparatus. Incremental equations were calibrated separately for initially contractive and dilative soil samples. Then, they were applied to predict the undrained behaviour of saturated soil samples. In the case of contractive soils, the constitutive equations describe the effective stress paths leading to the static liquefaction. In the case of dilative soils, the effective stress path is different, as the mean effective stress initially decreases, and after passing the instability line, it starts to increase, asymptotically reaching the failure envelope. Theoretical predictions of undrained behaviour are supported by experimental data. The original feature of this paper is that one can predict the undrained behaviour of saturated granular soils on the basis of stress-strain characteristics of the same soil but dry or tested in drained conditions.
18
Content available A Study on Pre-Failure Deformations of Granular Soils
Sawicki A.
Archives of Hydro-Engineering and Environmental Mechanics
|
2007
|
Vol. 54, nr 3
183-206
EN
A simple model describing pre-failure deformations of granular soils is derived on the basis of a wide range of experimental data. The model is defined by two incremental equations describing the volumetric and deviatoric strains. Functions appearing in governing equations were determined from experiments performed in the triaxial apparatus, with additional measurements of lateral strains for some simple stress paths. These functions are different for loading and unloading, and have different shapes for contractive and dilative soil samples. The instability line is built into the structure of the model. The incremental equations were applied to predict the soil behaviour during anisotropic compression, including determination of the K0-line. Some basic statistical characteristics of the initial density index of investigated soils and deformations during isotropic compression are presented.
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