Modelling of a 3D excavation in finite element analysis

TLDR

The study investigates how different modelling assumptions affect wall and ground movements and structural forces in a retaining structure supporting a 3D excavation. The authors model square and rectangular excavations, compare them to axisymmetric and plane‑strain approximations, and base the geometry, construction sequence, and soil conditions on a proposed deep excavation at Moorgate, London, for the Crossrail project. The results demonstrate that the modelling approach is broadly applicable to infrastructure projects, deep basement car parks, and buried structures, informing their impact on surrounding areas.

Abstract

This paper investigates a number of issues related to the modelling of a retaining structure used to support an excavation in 3D finite element analyses. In particular, the effects of wall stiffness in different coordinate directions and the rotational fixity in the corner of the excavation are examined. Both square and rectangular excavations are analysed and compared with the equivalent axisymmetric and plane strain analyses, normally used as approximations for modelling purposes. The chosen geometry, construction sequence and soil conditions are based on a proposed deep excavation at Moorgate in London (next to the Moor House development), which will form part of an underground station for the Crossrail project. The objective of the study is to provide a detailed assessment of wall and ground movements and structural forces in the wall in the light of different modelling assumptions. The study has wider application to a variety of projects that include the development of infrastructure, the construction of deep basement car parks and buried structures, and the effect that these have on the surrounding areas.