3D failure envelope of a rigid pile embedded in a cohesive soil using finite element limit analysis

Abstract

In this paper, numerical limit analysis is applied to evaluate the bearing capacity of a single rigid pile embedded in a ponderable homogeneous cohesivefrictionless soil subjected to vertical, horizontal, and moment (VHM) loading combinations. All loads act in the same plane. Accurate lower and upper bounds are calculated using finite element limit analysis code OPTUM G3. As the gap between the bounds hardly exceeds 5%, the average limit load provides a good estimate of the exact ultimate load and can be used with confidence for design purposes. By adopting typical values for the dimensionless pile length-todiameter ratio, most cases of practical interest are treated. The numerical results are compared against failure surfaces predicted by theories from the literature. Comparison shows that previously developed methods can be conservative or slightly overestimates the limit loads. New design charts are provided. The safe loads domain is constructed in the VHM space using the average limit load. Closed-form expressions are proposed to describe the native and the normalized VMH failure envelope as a function of the pile length-to-diameter ratio. In the VH plane, the failure surface is described by an eccentric superellipse, whereas in the MH plane, the limit curve is an inclined ellipse.

Assessment of the Bearing Capacity of Bridge Foundation on Rock Masses

“…The use of numerical methods and the progress of computational geomechanics have allowed access to the practical calculation of more sophisticated bearing capacity problems involving: (a) anisotropic rock masses (in [26] a solution in some simple cases is indicated and in [27] another solution for piles in rock masses is developed but in both cases the solutions do not depend on the width); (b) the presence of a water table in the rock [28], the shape of the foundation in rock masses [29], and roughness of the rock [30] where the results do not incorporate the size foundation; (c) the interaction with other structural elements such as tunnels [31] where it is not possible to know the influence of the dimension of the foundation; (d) bilayer rock under the footing [32] that does not depend on the width of footing; (e) the dynamic response of the foundation that offer solutions that do not depend on the geometric characteristics of the analyzed foundation (in [33] and [34] cases without self-weight of the ground are considered, [35] a particular application is considered but it is not possible to obtain the influence of the foundation size). In addition, new calculation methods have been developed in the study of piloted foundations in non-cohesive soil [36], cohesive soil [37], and considering inclined load [38] but using a linear failure criterion not representative of the behavior of a rock masses.…”

The Influence of the Shaft on the Uplift Capacity of Single-Plate Helical Pile in Clay

“…In recent years, FELA has shown strong capabilities and reliability in analyzing plane strain problems [21,22] and 3D problems [23][24][25]. The FELA program OptumG3 was utilized for all analyses conducted in this study.…”

Robust limit analysis theory for computing worst-case limit loads under uncertainties

“…For instance, assessing the bearing capacity of a footing usually assumes a single vertical loading. In order to account for additional lateral loading or applied bending moment to the footing, complex interaction diagrams must be determined for all possible loading combinations, inducing large computational costs (Kusakabe and Takeyama, 2010;Graine et al, 2021). To simplify this procedure, it would therefore be relevant to compute the reduced bearing capacity relative to a dominant vertical loading accounting for uncertainties in the value of secondary loadings (lateral force or bending moment).…”