Automated numerical modelling for the control of EPB technology

Tunnelling is often considered an exclusive field of experts with countless years of practice mostly because of a grey area existing between design carried out with sophisticated theories and construction ruled by practical judgement. Despite the auxiliary actions carried out during execution are acknowledged to affect significantly the interaction between soil and lining, limited effort is made to analyse their effects with an appropriate theoretical support, often preferring to perform broad estimate with arbitrary coefficients. The present paper aims to establish a common field between designers and executors, trying to take advantage on one side of the increased power of numerical computation, on the other side of the accurate control of equipment nowadays available. A three-dimensional numerical model is then built to simulate tunnelling with Earth Pressure Balance, characterising with great detail the properties of the various materials and the geometrical and mechanical characteristics of excavation. The calculation is superintended by a script that automatizes the assignment of input and the interpretation of output, allowing in this way to perform repetitive parametric analyses. The tool is firstly tested on a real case study, a section of the MRTA project of Bangkok, then applied to quantify the effects of the pressure applied on the tunnel face and of the gap left between lining and soil. The calculation shows the time evolution of the mechanisms induced by excavation and lining installation and their modification induced by a parametric change of the main technological factors.