This paper presents a three-dimensional analysis of a
trapezoidal-shaped segmental tunnel lining for a recent tunnelling project in
Sydney. Two- dimensional analyses, hand calculations and equipment selection
defined the lining geometry and loads. The analysis, which was undertaken using
3DEC (Itasca), included a complete ring of six segments bolted together to
assess the impact of imperfectly built rings. Asymmetry was induced in the
analysis by unfavourable positioning of segments within construction tolerances.
Model output includes displacement and stress within the entire ring and normal,
shear and bending moments at the joints. For the case analysed, the results
suggest a 10 mm construction tolerance increases normal and shear stresses along
the radial joints by approximately 25 per cent and 15 per cent, respectively and
up to a doubling of the induced moments.