A simplified analysis method for piled raft and pile group foundations with batter piles

Abstract

SUMMARYA simplified method of numerical analysis has been developed to estimate the deformation and load distribution of piled raft foundations subjected to vertical, lateral, and moment loads, using a hybrid model in which the flexible raft is modelled as thin plates and the piles as elastic beams and the soil is treated as springs. Both the vertical and lateral resistances of the piles as well as the raft base are incorporated into the model. Pile-soil-pile, pile-soil-raft and raft-soil-raft interactions are taken into account based on Mindlin's solutions for both vertical and lateral forces. The validity of the proposed method is verified through comparisons with several existing methods for single piles, pile groups and piled rafts. Workable design charts are given for the estimation of the lateral displacement and the load distribution of piled rafts from the stiffnesses of the raft alone and the pile group alone. Additionally, parametric studies were carried out concerning batter pile foundations. It was found that the use of batter piles can efficiently improve the deformation characteristics of pile foundations subjected to lateral loads.

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

“…This value is in close agreement with that previously estimated from the chart proposed by Poulos and Davis [6]. The limited effect should be attributed to the layout of the reaction piles, given that for cross tension piles configuration in the same spacing as above, the stiffness overestimation of the test pile head exceeds the level of 200% [15,24]. A reduction of the interaction effect between the tested pile and the reaction piles starts when yielding of the soil surrounding the pile begins to take place and the soil is unable to follow the stress field induced by the tension piles.…”

“…According to Fleming et al [23], Poulos and Davis [6], and Kitiyodom and Matsumoto [24], the overestimation may be very significant when the reaction piles are close to the test pile. As pointed out by Comodromos et al [15], the effect is due to the earlier mobilization of the shear strength of the soil between the pile under test and the reaction piles.…”

A simplified analysis method for piled raft foundations subjected to ground movements induced by tunnelling

“…where ½A is the soil flexibility matrix. The diagonal coefficients of ½A are determined by inverting the soil spring stiffness matrix ½K s : The details of the soil spring stiffness values can be found in References [2,3]. The offdiagonal non-zero coefficients in the matrix ½A represent structural member-soil-structural member interactions and are calculated based on Mindlin's solutions for both vertical and lateral forces.…”

“…Hence, a feasible but reliable deformation analysis method for piled raft foundations would be useful. As a preliminary routine design tool of a piled raft foundation subjected to combined external loading (vertical, lateral and moment loads), a computer program PRAB (Piled Raft Analysis with Batter piles) has been developed by Kitiyodom and Matsumoto [2,3]. In Reference [4], the program was extended to accommodate three-dimensional simplified analysis of piled raft foundations subjected to ground movements.…”

Surface displacements due to batter piles driven in cross‐anisotropic media

“…In general, batter piles (or raked piles) are chosen to support the offshore structures, bridge foundations, and towers [1][2][3][4][5][6][7]. In particular, when significant lateral loads are to be resisted by a pile group, it has been common practice to use piles driven at a slope with respect to the vertical 122 C.-D. WANG, M.-T. CHEN AND T.-C. LEE [8,9].…”