Numerical analysis of a tunnel behaviour considering the spatial variability of the geotechnical parameters

This study applies random field theory to simulate the spatial variability of the ground where a tunnel was excavated in a granitic soil mass, in the city of Porto (Portugal). Numerical analyses are performed using finite element method combined with random field theory to simulate tunnel excavation. A parametric study to analyse the influence of the correlation coefficient is performed. The results are compared with the measured values and the values obtained with the deterministic computation. The performance of the models is evaluated using two measures of error: root mean squared error (RMSE) and mean absolute deviation (MAD). With the random fields approach (correlation length equal to 0.5) values of MAD equal to 2.18 and RMSE equal to 4.16 were obtained, whereas with the deterministic approach values of MAD equal to 2.29 and RMSE equal to 4.26 were obtained. Furthermore, the performance of the models improves as far as the correlation coefficient increases. Therefore, it is concluded that the results obtained using random fields are better than those obtained using the deterministic analysis.