1,720,962 research outputs found
3M Analytical method: evaluation of shaft friction of bored piles in sands
No full textThis study presents 3M, an analytical method to estimate the skin friction of bored piles in sands. It is based on the fundamental mechanic behavior of sands and keeps track of the major mechanisms occurring in the soil close to the pile during loading. These include the development of a shear band, its potential expansion as induced by soil dilatancy, and the ensuing increment of horizontal stresses owing to the restraining effect of surrounding soils. The resulting analytical equations are easy to apply and insert in a worksheet. The procedure to evaluate the shear band expansion is calibrated against results of direct shear tests at constant normal load, whereas the increment of horizontal stresses is evaluated by the closed-form solution for the expansion of a cylindrical cavity into a dilatant elastic–perfectly plastic medium. The effectiveness of the 3M method in predicting shaft friction has been checked against numerical results, centrifuge, and full scale pile load tests. Nevertheless, prior to use in design practice, preliminary validation is required with more well-documented experimental data from load tests on instrumented bored piles
Effetti della dilatanza parzialmente impedita sulla resistenza laterale dei pali trivellati in sabbie
No full textUn metodo analitico per la valutazione della resistenza laterale di pali trivellati in terreni sabbiosi
No full textComportamento di una platea su pali infissi staticamente durante la sua costruzione e nelle prime fasi di esercizio
No full textRational Design of Piled Raft
No full textAbstractPiles have been traditionally designed to ensure the transfer of the whole structural load to the soil in which they are embedded. It is now largely accepted that this way of doing is unduly conservative, especially in those cases in which an unpiled raft is sufficient to guarantee a satisfactory safety level. Nevertheless, it is still very common in the daily practice, sometimes for the restrictions imposed by local codes and regulations.Much research efforts have been dedicated to a more rational design of piled foundations, essentially based on a proper collaboration among raft and piles not only for increasing the overall stiffness of an unpiled raft but, if required, also for increasing its capacity, for controlling differential settlements, for reducing the state of stress into the raft. With no claim to cover any single aspects, some design options will be presented, providing some insight into a rational approach to piled raft design
Un metodo semplificato per l’analisi non lineare del comportamento di platee su pali
Full text linkNella presente nota viene illustrato un metodo di analisi semplificato dell’interazione piastra-pali-terreno in presenza di carichi verticali. Il metodo tiene conto del comportamento non lineare del contatto piastra-terreno e del gruppo di pali; non consente di prevedere la ripartizione del carico fra i pali, fornendo invece come risultato le curve carico-cedimento della piastra su pali e le due aliquote di carico trasmesse dalla platea al contatto fra questa e il terreno e dal gruppo di pali. Il metodo è stato validato mediante soluzioni di riferimento pubblicate in letteratura
A numerical approach to estimate shaft friction of bored piles in sands
Full text linkA new approach to estimate shaft capacity of bored piles in sandy soils, based on numerical analysis, is presented. The topic is relevant as current design methods often largely underestimate the shaft capacity of piles in sands, thus resulting in an over-conservative design. The proposed approach is based on explicitly modelling the thin cylinder of soil surrounding the pile, where strain localization concentrates (shear band), and on the fundamental mechanic behaviour of sandy soils (e.g. dilatancy, softening). This approach is both simple and easy to apply. Results of a broad parametric study involving axially loaded single piles embedded in different sandy soils are presented, highlighting that relative density and grain size distribution mainly affect the shaft capacity. The capability of the procedure to predict shaft friction is checked against data from a well-documented full-scale axial load test on instrumented pile. Some suggestions for calibration and application of the method are also reported. © 2014 Springer-Verlag Berlin Heidelberg
Effects of residual stresses on shaft friction of bored cast in situ piles in sand
No full textThe existence of residual stresses locked-in prefabricated displacement piles is a well-known problem and has been
addressed by a number of researchers in the last decades. This is not the case with cast in situ piles: as a consequence of concrete
curing, pile-soil interaction starts soon after concrete casting, causing stress changes in terms of both normal and shear stresses.
Such circumstance has been confirmed by few experimental evidences, reported in the paper, in saturated or dry soil conditions.
In order to evaluate the influence of residual stresses on the subsequent pile response to axial loading, a broad parametric
study has been carried out by means of numerical modelling. Particular focus is given to the effects induced on the shaft friction
of floating bored piles embedded in wet and dry sandy soils.
The results have been interpreted with the aim of highlighting errors commonly made if a stress-free pile is assumed when
interpreting a specific load test results on instrumented piles and/or arranging general design methods
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