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1

Setup of axial bearing capacity of open ended tubular steel piles driven in sand

Ahlinhan Marx Ferdinand, Adjovi Edmond Codjo

Studia Geotechnica et Mechanica

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2020

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Vol. 42, nr 1

74--82

EN

This paper focuses on the setup of axial bearing capacity of open ended tubular steel piles that are used for offshore foundation systems such as those of wind turbines. A comparative evaluation of the most commonly used models for setup prediction shows an upper estimate bound and a lower estimate bound, which correspond approximately to a setup rate of 60% increase per log cycle of time and 20% increase per log cycle of time, respectively. This finding is validated with the results of case histories reported in literature, which show that the setup values of most case histories considered lie in the best estimate zone between the upper estimate zone and the lower estimate zone. The analysis results show a minimum setup factor of approximately 1.5 for 100 days following end of driving of open-ended tubular steel pile driven in sand.

2

Model experiments to assess effect of cavities on bearing capacity of two interfering superficial foundations resting on granular soil

Saadi Djamel, Abbeche Khelifa, Boufarh Rafik

Studia Geotechnica et Mechanica

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2020

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Vol. 42, nr 3

222--231

EN

The objective of this paper is to describe the effect of cavities on the bearing capacity of two interfering footings based on granular soil using an exclusively experimental approach with a test model designed in the laboratory. The experimental protocol was carried out based on the variation of several parameters such as the spacing (x) (axis to axis) between the footings, and the distance (H) between the footings and cavities and between the cavities axes (L). The results highlight the effect of cavities and the interference of two strip footings on the bearing capacity factor (q) and efficiency factor (EF). Moreover, the results revealed that, in the case wherein the distance between the footings and the cavity is greater than 3, the cavity impact is eliminated.

3

State-dependent fractional plasticity model for the true triaxial behaviour of granular soil

Sun Y., Sumelka W.

Archives of Mechanics

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2019

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Vol. 71, nr 1

23--47

EN

The fractional plasticity was proposed to model the stress-strain behaviour of granular soils, but only within the scope of classical triaxial loading condition. In this study an attempt is made to develop a 3D fractional plasticity model for granular soils subjected to true triaxial loads by using characteristic stress, where all the fractional-order and integer-order derivatives can be easily obtained. Without using a plastic potential, the non-associated plastic flow rule is achieved by performing fractional derivatives of the yielding function in the characteristic stress space. The obtained plastic flow direction is found to be influenced by the fractional order, characteristic stress parameter and intermediate stress ratio. To further validate the proposed model, a series of true triaxial test results of different granular soils are simulated, from which good agreement between the model predictions and the corresponding test results is found.

4

Constitutive modelling of root-reinforced granular soils – preliminary studies

Świtała B., Fern E. J.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2018

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Vol. 27, No. 2

103--113

EN

A novel solution for the problem of modelling of soil reinforced with vegetation roots. An extension of the Nor–Sand model and its application to granular saturated or dry, soil–root composites. Model implementation in MATLAB: numerical simulations of drained triaxial compression tests, investigation of the sensitivity of the solution to different values of model parameters. Capturing the most important features of soil–root composites. Accounting for the progressive activation of the root’s strength. Indication of the ability of further model application to large-scale problems, such as slope or dune stability.

5

Structure and calibration of constitutive equations for granular soils

Sawicki A., Sławińska J., Mierczyński J.

Studia Geotechnica et Mechanica

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2014

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Vol. 36, nr 4

35--46

EN

The form of incremental constitutive equations for granular soils is discussed for the triaxial configuration. The classical elasto-plastic approach and the semi-empirical model are discussed on the basis of constitutive relations determined directly from experimental data. First, the general structure of elasto-plastic constitutive equations is presented. Then, the structure of semiempirical constitutive equations is described, and a method of calibrating the model is presented. This calibration method is based on a single experiment, performed in the triaxial apparatus, which also involves a partial verification of the model, on an atypical stress path. The model is shown to give reasonable predictions. An important feature of the semi-empirical incremental model is the definition of loading and unloading, which is different from that assumed in elasto-plasticity. This definition distinguishes between spherical and deviatoric loading/unloading. The definition of deviatoric loading/unloading has been subject to some criticism. It was therefore discussed and clarified in this paper on the basis of the experiment presented.

6

Zastosowanie metody Gaussowskiego procesu do identyfikacji charakterystyk zagęszczenia gruntów ziarnistych

Kłos M., Słoński M., Waszczyszyn Z.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2012

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z. 59, nr 3/IV

41-48

PL

W pracy zastosowano metodę bayesowską Gaussowskiego Procesu (GP). Metoda wyróżnia się brakiem wektora wag i użyciem funkcji kernelowskich oraz macierzy kowariancji w przestrzeni danych wejściowych. Dzięki temu w GP można było formułować stosunkowo proste algorytmy i procedury komputerowe. GP zastosowano do identyfikacji dwóch charakterystyk zagęszczenia gruntów ziarnistych, tj. wilgotności optymalnej oraz maksymalnej gęstości objętościowej. Celem sprawdzenia numerycznej efektywności GP zastosowano ją do analizy nowych danych pomiarowych opisanych w [2], analizowanych w [4] za pomocą semi-baysowskiej sieci neuronowej (SBNN). Wykazano, że dokładność identyfikacji metodą GP jest porównywalna z zaletami SBNN.

EN

In the paper the Gaussian Process (GP) model is discussed as a simple Bayesian for approach to identification analysis. In GP model the weight vector is not applied, which makes the algorithms and computational procedures simpler than those formulated in the Semi-Bayesian Neural Network (SBNN). In the paper it was numerically proved that the application of GP to the identification of compaction parameters for granular soils is numerically efficient, comparable for GP and SBNN applications.

7

Analiza teoretyczna zagęszczania nawodnionych gruntów ziarnistych metodą mikrowybuchów

Dembicki E.

Zeszyty Naukowe. Budownictwo / Politechnika Śląska

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2007

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z. 111

59-82

PL

W pracy przedstawiono opis zjawiska fizycznego w nawodnionym gruncie ziarnistym wywołanego kulistym ładunkiem wybuchowym. Opisano mechanizmy zagęszczania, przytoczono przykłady zastosowania zagęszczania gruntów metodą mikrowybuchów i podano wnioski, wynikające z badań laboratoryjnych i terenowych zagęszczania, służące do opracowania analizy teoretycznej. Analiza teoretyczna oparta jest na propagacji fali uderzeniowej wywołanej kulistym ładunkiem wybuchowym umieszczonym w nieograniczonej pół-przestrzeni. Podstawowe równania do opisu rozpatrywanego zagadnienia oparte są na mechanice continuum i równaniach konstytutywnych ośrodka trójfazowego (grunt ziarnisty + woda + gaz) zaproponowanych przez G. M. Lachowa. Sformułowano podstawowe równania wyjściowe i warunki brzegowo-początkowe przyjęte do rozwiązania. Rozwiązanie numeryczne obejmuje określenie: promienia kulowego otworu zagęszczającego, promienia obszaru zagęszczenia oraz średniego stopnia zagęszczenia zagęszczonego obszaru. Wyniki obliczeń przedstawiono w postaci nomogramów. Ponadto, przedstawiono oszacowanie skuteczności zagęszczenia gruntu metodą mikrowybuchu.

EN

The paper contains a description of the physical phenomena which occur in a saturated granular soil as a result of underground explosions which this process entails. The mechanisms of compaction, the examples of application and the conclusions from the laboratory and field tests are presented. A theoretical analysis of a saturated granular soil compaction by means of the blasting method is presented. Łwestigations arę based on propagation of a high-impact shock wave produced by a spherical charge placed in an unconfined half-space. Basic equations describing the problem are derived from physical continuum mechanics methods and from constitutive equations for a three-phase medium (granular soil + water + gas) as proposed by G. M. Lachów. Non - compressive soil medium is assumed in the solution. Basic eąuations are deduced and the initial - boundary problem is formulated. The numerical calculations carried out allow: the spherical soil radius, the radius of the compacted area and the mean compaction degree of the affected zone to be determined. Calculation results are presented in nomograms. In addition, an estimate of the efficiency of soil compaction using the blasting method is provided.