Evidence of beneficial role of inclined piles: observations and summary of numerical analyses

Abstract

The behaviour under seismic loading of inclined piles embedded in two idealized soil profiles, a homogeneous and a non-homogenous "Gibson" soil, is analysed with 3D finite elements. Two structures, modeled as single-degree-of-freedom oscillators, are studied: (1) a tall slender superstructure (H st = 12 m) whose crucial loading is the overturning moment, and (2) a short structure (H st = 1 m) whose crucial loading is the shear force. Three simple two-pile group are studied: (a) one comprising a vertical pile and a pile inclined at 25 • , (b) one consisting of two piles symmetrically inclined at 25 • , and (c) a group of two vertical piles. The influence of key parameters is analysed and non-dimensional diagrams are presented to illustrate the role of raked piles on pile and structure response. It is shown that this role can be beneficial or detrimental depending on a number of factors, including the slenderness of the superstructure and the type of pile-to-cap connection.Keywords Inclined pile · 3D finite element model · Seismic response · Group of piles · Pile-to-cap connection · Soil-pile-bridge pier interaction · Field observations

Kinematic internal forces in deep foundations with inclined piles

“…The conclusions drawn here for the case of the pile group are in line with those reached in previous studies by Deng et al [5], Giannakou et al [4,1] and Gerolymos et al [6], and seem to confirm that pile inclination tend to produce larger kinematic internal forces around pile heads in comparison to vertical piles, although maximum kinematic bending moments and shear forces tend to decrease significantly along the deepest two thirds of the piles. However, there are several aspects of the topic that need further analysis:…”

“…The assumption of hinged pile-to-cap connections modify the kinematic response of the pile, as shown by Ginnakou et al [4], Gerolymos et al [6] and Sadek and Shahrour [3]. As expected, the assumption of hinged pile-to-cap connections affects mainly the distribution of maximum bending moments.…”

“…Kinematic axial forces increase in all cases with pile inclination, both at pile heads and along all the pile buried length, which could lead to detrimental consequences such as an increased risk of buckling or a reduction in bending capacity [6].…”

“…Several numerical [2,3,4,5,6,1,7] and experimental [8,9,10] studies have already looked into the seismic response of raked piles reaching very interesting conclusions for several particular cases. These results seem to confirm that inclined piles might develop kinematic forces at the pile-cap connection larger than those observed in their vertical counterparts, but they also suggest that batter piles might be beneficial in terms of the total response.…”

Kinematic Stress Resultants in Inclined Single Piles Subjected to Prapagating Seismic Waves: An Analytical Formulation

“…On the contrary, applications of such approaches to inclined piles are not so popular in the literature and more sophisticated finite element or boundary element models are preferred [2][3][4][5][6][7].…”