ABSTRACT
A review on 49 available publications has found that tunnelling analyses were carried out with different mesh configuration particularly on the above-mentioned factors, which ranges from very narrow to wide meshes or very shallow to deep meshes and to no debate which mesh configuration is appropriate and the effect on the result as given in Table 1. The review also shows that analyses were carried out both with and without the lateral fixity at the bottom boundary of the mesh (60% with pinned fixity where as 36% on
ABSTRACT: As ground is practically an unbounded medium, selection of only a small area around a tunnel for analysis purpose is sure to introduce some errors. Also the boundary conditions imposed on these boundaries will influence the shape and magnitude of displacement profiles. This paper investigates effect of boundaries on predicted ground movements due to tunnelling in plane strain analysis. A review of published finite element analyses was carried out and general observations on the magnitudes and trends of movement are summarised. Subsequently, a detailed parametric study was carried out to identify the factors which influence mesh size. It is shown that the size of mesh required is highly dependent on the C/D ratio, soil model, Ko condition and the boundary fixity. A mesh configuration scheme is proposed to obtain sizes of mesh to produce near mesh-independent results.
