Analysis of Pile Group Behavior

Abstract

A procedure for the three-dimensional analysis of pile groups subject to horizontal and vertical forces and moments which accounts for batter piles, the flexural resistance of the piles, and the lateral resistance of the surrounding soil is discussed. Due to the extensive amount of computational effort required to analyze a pile group, the analysis was programmed for a digital computer. Since many of the factors involved in the design of pile foundations are not known with great accuracy, the use of the digital computer permits the esigner to examine the effect of variations in various design parameters. This paper presents results obtained from analyzing several pile group arrangements for various soil and loading conditions. The results obtained from the analysis include the axial loads, moments, stresses, and deflections for individual piles, as well as for the group. The numerical results obtained from analyzing various illustrative examples show the significant influence that the following factors have on the loads that are introduced in the various individual piles: (a) the arrangement of the individual piles within the group, (b) the end condition as reflected by the connection between the pile cap and the piles, (c) the lateral resistance of the surrounding soil, and (d) the flexural resistance of the pile. Comparison with field and laboratory tests indicates that the behavior of pile groups predicted by the analysis is in qualitative agreement with observed behavior. This paper demonstrates that it is possible to use the pile group analysis presented as a practical method for solving design problems. The ability to evaluate variations in design parameters should lead to safer and more economical designs.