3D numerical models require significant time and cost for their preparation and execution. It is in the hands of the

engineer to set the optimal level of simulation detail that will provide a reliable and cost effective solution. In

sprayed concrete lining tunnels, a common simplification is to simulate the excavation with full face steps. This

assumption can prove effective in minimising the modelling and analysis requirements and can be utilised to check

the structural capacity of the concrete lining, but the calculated in-tunnel and surface deformations, which is often

the project’s deliverable, may not be adequately predicted.

The effect of simulating varied excavation sequences of a sprayed concrete lining tunnel on the 3D numerical

analysis results, was investigated in this study. The excavation of a 20m long tunnel, 11.2m high and 10.4m wide

which is being enlarged from an existing TBM tunnel (6.4m OD) was simulated using 3 different excavation

sequences: i) full face, ii) top heading, bench invert and iii) top heading, invert bench. Moreover, the effect of

applying intermediate soil relaxation factors prior to the installation of the lining was also considered. The models

were calibrated against real measurements.

Based on this study, the efficiency of various simulation approaches is evaluated and a derivation of adjustment

factors that can be applied on the results of the simplified, full-face excavation models is proposed.