Load transfer approach for the geotechnical analysis of energy piles in a group with slab

Elena Ravera,Lyesse Laloui,Melis Sutman

doi:10.1051/e3sconf/202020505008

Abstract

Thermally induced group effects characterise closely spaced energy piles. It has been observed experimentally that the behaviour of energy piles subjected to mechanical and thermal loads, in which the piles are located sufficiently close to each other, is different from the behaviour of single isolated piles. Therefore, civil engineers encounter new challenges in the geotechnical design of such foundations. This leads to the necessity to develop practical tools to address their analysis and design. The conventional load transfer method is one of the commonly used methods for the analysis of axially loaded conventional piles. Thus, the purpose of this study has been to propose a formulation of the load transfer method to consider the thermally induced effects among energy piles in groups. The soil response is characterized in a lumped form by ascribing the behavioural features of the soil to interface elements. The individual response, in terms of strain and stress of an energy pile in a group, can be addressed for the first time through the application of the displacement factor in the load displacement curve of the single isolated energy pile. A validation through a full-scale field test reveals the capability of the approach to provide the necessary information in the analysis and design phases of the foundation for one-way thermal loads.

Highlights

The load transfer method was first proposed by Coyle & Reese [1] to address the analysis of axially mechanically loaded single piles
The goal of this study is to propose a formulation of the load transfer method to consider the thermal and mechanical interactions among energy piles in group
A simplified method was presented which allows to estimate quantities of paramount importance for engineering applications such as the vertical displacement, vertical stress and mobilised shaft resistance of an energy pile in group subjected to thermo-mechanical load

Summary

Introduction

The load transfer method was first proposed by Coyle & Reese [1] to address the analysis of axially mechanically loaded single piles. The main feature of the method is that the continuity of the soil domain is ignored and the pile-soil interaction is represented by springs. Each of these springs is characterised by a constitutive law. The method is considered an effective analysis approach to address the energy pile capacity and deformation caused by axial mechanical and thermal loads [12]. The goal of this study is to propose a formulation of the load transfer method to consider the thermal and mechanical interactions among energy piles in group. The proposed approach provides information of paramount importance for engineering applications such as the vertical displacement, the vertical stress and the mobilised shaft

Load transfer method for energy pile groups

Implementation of the method

Application and validation of the method

Model parameters

Results and discussion

Conclusion