Response evaluation of axially loaded fixed‐head pile groups in clayey soils

Abstract

SUMMARYThe aim of this paper is to investigate the interaction between the piles in a group with a rigid head and correlate the response of a group of piles to that of a single pile. For this purpose, a computationally intensive study using 3-D nonlinear numerical analysis was carried out for different pile group arrangements in clayey soils. The responses of the groups of piles were compared with that of a single pile and the variation of the settlement amplification factor R a was then quantified. The influence of the number of piles, the spacing, and the settlement level on the group response is discussed. A previously proposed relationship for predicting the response of a pile group, based on its configuration and the response of a single pile, has been modified to extend its applicability for any pile spacing. The modified relationship provides a reasonable prediction for various group configurations in clayey soils.

Pile foundation analysis and design using experimental data and 3-D numerical analysis

“…It can be observed that both 2 Â 2 and 3 Â 3 group configurations demonstrate the same mean ultimate bearing capacity, defined as the ultimate capacity of the group divided by the number of piles in the group. On the contrary the group mean stiffness, defined as the stiffness of the group divided by the number of piles, clearly depends on the number of piles, justifying the findings of previous researchers [7,14,16], who state that when the pile number increases the group mean stiffness decreases as a result of pilesoil-pile interaction. It must be underlined that this is valid for low level settlements, since, as soil yielding occurs the effect of the interaction decreases and finally leads to the coincidence of loadsettlement curves, as can be observed in Figs.…”

“…The application of this relationship was limited to the commonly applied pile spacing of 3.0b and to soil profiles similar to the one used in the analysis. With the aim of examining the validity of the proposed relationship to different soil profiles, Comodromos and Bareka [16], carried out an extensive numerical analysis for various pile dispositions and different soil profiles, covering the range from very soft to hard clays. According to their results, the proposed relationship was able to predict the response of a fixed head pile group in clayey soils with a reasonable level of accuracy.…”

A finite element–based approach for predictions of rigid pile group stiffness efficiency in clays

“…13c, it is evident that existing nonlinear predictions of η g documented by Comodromos and Bareka [25], using the finite difference code FLAC 3D [26] are slightly lower than field data while predictions documented by Castelli and Maugeri [8] are significantly greater. The exponent of 0.15 in the approach documented by Castelli and Maugeri [8] was derived from a limited database of case histories, not all of which were friction pile groups.…”

“…13c, predictions of η g using the HS model in PLAXIS have been compared to existing nonlinear analyses and empirical methods [8,25].…”

“…and 100 using the HS model in PLAXIS and plotted along with the results by Comodromos and Bareka [25]. Poulos [27] noted, however, that the reduction in the 'near-pile' soil stiffness results in reduced pile-to-pile interaction; therefore in the …”