Development of a three‐dimensional soil model for the dynamic analysis of end‐bearing pile groups subjected to vertical loads

Abstract

Summary This paper presents a new analytical model for calculating the steady‐state impedance of pile groups subjected to vertical dynamic loads. The derived solution allows considering effects of radially but also vertically propagating soil waves on the soil attenuation function, pile interaction factor, and pile group impedance. The proposed model provides accurate estimates of the soil stress field and of the response of the pile group in the low as well as in the high‐frequency range, unlike earlier solutions based on the plane‐strain model to describe the soil surrounding the piles, which ignores the vertical soil stress gradient. The latter assumption results in underestimating pile group impedance and overestimating radiation damping for frequencies lower than the cutoff frequencies of the system, which are explicitly captured with the proposed solution.

Vertical dynamic impedance of end‐bearing pile groups embedded in homogeneous unsaturated soils

“…It can be seen from the Figures 2−4, although the reduced solutions match well with those of Luan et al., 43 small discrepancies can still be observed between the reduced and existing solutions. This is because the radial displacement of soil was ignored while solving for the shear stress in Ref. 43 Consequently, we can conclude that the cut‐off frequencies of pile−soil system have little connection with the shear stress.…”

“…To verify the accuracy of the proposed solution for pile groups embedded in unsaturated soils, the reduced solutions of the attenuation function, pile-to-pile interaction factor, and dynamic impedance of a 2 × 1 pile group as calculated in this work are compared with the solution for pile groups embedded in single-phase soils as derived by Luan et al 43 In addition, to investigate the differences between a three-dimensional continuum model and a plane-strain model, we compare the results of the proposed model with those of the plane-strain model proposed by Mylonakis and Gazetas. 36 As described previously, the strain in the vertical direction is ignored in the plane-strain model, and the waves propagate only in the horizontal direction.…”

“…[37][38][39][40][41][42] In contrast, there have been relatively few analogous studies of pile groups. Luan et al 43 investigated the vibration response of pile groups using pile-to-pile dynamic interaction factors defined by displacement. Soon afterward, considering the pile geometry effect, Luan et al [44][45] proposed new pile-to-pile dynamic interaction factors for the vibration response of pile groups embedded in single-phase soils.…”

Vertical vibration of piles with square cross‐section

“…For the case of pile group, calculating the dynamic impedance of pile group is generally based on the superposition method, which is originally proposed for the static problem and afterwards applied to dynamic problems by Dobry and Gazeta, 27 Gazetas and Makis, 28 Wang et al., 29 Luan et al 30 . The recent studies 31,32 have proved the efficiency of superposition method using appropriate interaction factors through finite element simulation.…”

Simplified three‐dimensional analysis of horizontally vibrating floating and fixed‐end pile groups

“…Individual piles arranged in a group to transfer loads to the subsoil interact not just with their surrounding soil, but also with other piles in their group. This phenomenon is referred to in the literature as “pile‐pile interaction” and in dynamically loaded groups is attributed to propagation of ground waves generated by the vibration of piles, which introduce additional displacements on neighboring piles.…”