19 research outputs found
DEM element modelling of silent piling group installation for offshore wind turbine foundations
No full textOffshore wind farms are now built in deeper water and bigger foundations are required to stabilise wind turbines of increasing sizes. Pile driving is the most widespread foundation installation method, but more stringent environmental regulations necessitate costly mitigation methods to reduce underwater noise emissions. The silent piling (push-in) concept presented in this work is composed of a cluster of four piles, progressively installed by successive jacking sequences. During one sequence, each pile is moved downward by 0.5m stroke, while the other piles are used as reaction. This paper presents the results of Discrete Element Method (DEM) of the installation process. This work identifies the main features of the push-in installation method, such as pile interaction, progressive plugging and loss of efficiency as a function of depth. It is shown that the cluster capacity can reach six times the weight of the tool necessary to silently install the piles
Control of screw pile installation to optimise performance for offshore energy applications
No full textScrew piles can be used as foundations for offshore energy applications, thanks to their silent mode of installation and considerable uplift capacity, although a significant upscaling of onshore dimensions will be necessary. However, the crowd (vertical) force necessary to install upscaled screw piles was previously shown to be far too great for practical installation. Whilst guidance recommends that the pile vertical displacement must be one helix pitch (helix height) per each pile revolution, it is shown in this paper that a lower vertical displacement per revolution can significantly reduce the necessary crowd force during installation or even generate some pull-in. In addition, it was shown that the uplift stiffness and capacity of the pile were enhanced by this installation process, at a shallow (relative) depth in sand. This paper gathers nineteen centrifuge tests, with varying screw pile geometries (shaft diameter, base shape), sand relative density and advancement rates. A predictive framework for the pull-in potential of a given pile geometry was proposed to assess its ability to be installed with a reduced crowd force
Design optimisation of deep pile foundations installed by static forces
No full textThis paper presents preliminary experimental and analytical investigations of the push-in pile concept, which aims at installing piles in the offshore environment without significant underwater noise. The concept replaces a large diameter pile with a cluster of closely spaced smaller piles. The piles are installed progressively by cycles of jacking. During each cycle, a pile is successively pushed downwards or moved upwards while used as a reaction pile. This process was physically modelled in a geotechnical beam centrifuge and a predictive model was developed and calibrated against these tests. A parametric study was then undertaken to optimise the cluster design and reduced the tool weight necessary to achieve a given installation depth or cluster capacity. Smaller pile diameters are more beneficial to reduce the necessary tool weight during the cluster installation, but require much longer piles to achieve the target capacity. The full optimisation of a cost-effective pile cluster will require additional constraints, such as the lateral capacity (not investigated here) and expected installation time
Novel surface speckle preparation method for imaging techniques for clay models
No full textA novel method for the application of contrasting speckle material on a clay sample was developed. In comparison to traditional methods, the new method minimises the sample disturbance resulting from sample handling and the removal of any transparent windows of the strongbox after the consolidation stage. This method applies the contrast material on the transparent window before it is released to the surface of the slurry, thus facilitating tracking of material displacements during the consolidation stage and subsequent loading stages. The method was successfully demonstrated for a centrifuge model test and a 1g model test, each with complex material deformations and rotations
Immediate & long-term installation effects adjacent to an open-ended pile in a layered clay
No full textFloating piles in soft soil deposits primarily mobilize their bearing capacity by means of shaft resistance. The upper part of the pile triggers a downward traction on the pile shaft whilst the lower part mobilizes the shaft friction in the soil required for the pile bearing capacity. The transition between these two modes of shaft friction is often defined as the neutral-plane. This plane, which is not at a constant level, assists in predictions of the (long-term) settlements of a pile in such a soil. Floating piles primarily occur in areas where stiffer clay layers are overlain by softer clay layers, e.g. on the west-coast of Sweden or in the Kaspian Sea. In the past the response of floating piles is extensively described using the neutral plane approach. This approach requires a reliable prediction of the soil settlements, which in turn are affected by the pile installation effects in the soil. Additional experimental evidence on the soil behaviour during, directly after installation and in the long-term is required if advanced numerical methods are considered and current analytical design methods to be improved. A novel approach to retrieve this experimental data on immediate and long-term pile installation effects in the geotechnical centrifuge is developed. An axisymmetric experimental test setup allows for measurement of full-field displacement as well as pore pressures during and after installation. This setup uses an instrumented wall with 40 pore pressure transducers. Additionally, an image sequence taken with a machine vision camera is used to extract the soil displacements by application of Particle Image Velocimetry (PIV). Due to natural low contrast of the kaolin clay used for the experiments a novel method for the application of contrasting speckle material on a clay sample is developed. This method applies the contrast material on the surface of the slurry without the need of removing the transparent window of the strongbox. Therefore tracking of the material displacements during the consolidation stage and subsequent loading stages using imaging methods is facilitated. The results of the experiments are generally in agreement with the framework reported in literature and indicate that pile installation effects, such as generation of excess pore pressure and change of the hydraulic conductivity in the soil due to remoulding, have an influence on the development on the neutral plane and therefore the prediction of the response of floating piles. Additionally, the results can be used to benchmark numerical calculations with advanced constitituve models.Geo-EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
Optimised screw pile design for offshore jacket foundations in medium-dense sand
No full textScrew piles are well-suited foundations for offshore jacket structures, as they can be installed without significant underwater noise and have a large axial capacity. However, installation requirements for such large piles must be reduced to enable their installation in the field. This study combines geometry and installation optimisation to lower force and torque installation requirements. An original pile geometry, composed of a large diameter upper section connected to a smaller diameter lower section by a transition piece, was tested in a geotechnical beam centrifuge. The advancement ratio (AR), describing the relative vertical movement per pile rotation, was varied below the threshold usually recommended. The results show that a low AR reduces the pile penetration resistance and even generates some pull-in, while the torque remains almost unaffected. The torque is mainly associated with the upper section of the pile, which has a greater diameter to resist lateral loading in service. The pile capacity in tension generally increases as AR is reduced and reaches a maximum for AR=0·5, while the compressive capacity reduces. It was shown that a simplified method can be used to estimate pile capacity, providing that some AR-dependent reduction factors can be calculated or assumed.</p
New method for full field measurement of pore water pressures
No full textA cost effective method to measure pore water pressures in mixed granular media is described using 40 miniature MEMS pore pressure transducers. High accuracy in a single point is exchanged for lower accuracy full field measurements adjacent to the strongbox wall. The system is easily de-aired and calibrated due to the fact that the transducers are installed inside the strongbox wall. Additionally, the proof of concept test shows that the transducers are sufficiently accurate for problems with large pressure difference such as consolidation of clay while being subjected to elevated stress levels in the geotechnical centrifuge
Il caso della Contessa Cornelia Zangheri ne' Bandi in due testi del secolo XVIII dal punto di vista del genere non-fiction
No full textPrzypadek hrabiny Cornelii Zangheri ne’ Bandi w dwóch tekstach XVIII w. z punktu widzenia gatunku non-fiction
Streszczenie
Artykuł przedstawia dwa teksty z XVIII w. dotyczące wydarzenia, które miało miejscew mieście Cesena w 1731 r.: Parere sopra la cagione della morte della Signora ContessaCornelia Zangheri ne’ Bandi cesenate esposto in una lettera al signor co. Ottolino Ottolini daGiuseppe Bianchini canonico di Verona oraz Relazione del funestissimo evento della SignoraCornelia Zangheri ne’ Bandi occorso li 20 Marzo 1731 in Cesena (anonimowy rękopis, któregoautorem jest prawdopodobnie Scipione Maffei). Te dwa teksty zostały poddane analiziez punktu widzenia gatunku non-fiction, aby odpowiedzieć na pytanie, czy stanowią oneprzykład tego gatunku, chociaż ante litteram.
Słowa kluczowe: non fiction, Giuseppe Bianchini, Cornelia Zangheri, XVIII w., kronika
The case of the Countess Cornelia Zangheri ne’ Bandi in two 18th century worksfrom non-fiction point of view
Abstract
The article presents the 18th century texts regarding an event that occurred in Cesena in1731: Parere sopra la cagione della morte della Signora Contessa Cornelia Zangheri ne’ Bandicesenate esposto in una lettera al signor co. Ottolino Ottolini da Giuseppe Bianchini canonicodi Verona oraz Relazione del funestissimo evento della Signora Cornelia Zangheri ne’ Bandioccorso li 20 Marzo 1731 in Cesena (anonymous manuscript whose author is most probablyScipone Maffei). Those two texts were analyzed from the non-fiction point of view in order toanswer the question whether they are examples of said genre, even if ante litteram.
Keywords: non fiction, Giuseppe Bianchini, Cornelia Zangheri, 18th century, chronicl
Anzianità e modelli residenziali (The problem of housing for an ageing population)
No full textThe article summarizes some results of a long-term research on architecture for all ages developed at the Milan Technical University, addressing the problems of the ageing society connected with the crisis of the welfare state in Italy and in Europe (fundings: EU FP4, Italian Ministry of Research, Lombardy Region) It presents the theoretical and methodological aspects of a general rethinking on housing design in areas of architectural and urban design, proposing a new design framework for stimulating, dynamic, and supportive habitats for the improvement of quality of life for older people. Introducing criteria that consider the house a fundamental resource for the social redemption and full recovery of individual aptitude of frail people to develop evolutionary life patterns, it comparatively evaluates some of the most recent researches in the field against innovative design hypothesis, developed by the author (and, in the preceding article, by his research group co-ordinated by Prof. G.D. Salotti), for a new type of assisted temporary housing, based on adaptive integration of spaces, furniture and technologies
