Page 234 - Numerical Analysis and Modelling in Geomechanics

PARAMETER ESTIMATION USING EXTENDED BAYESIAN METHOD 215

Figure 7.8 Variation of objective function by the variation of the geotechnical parameters
(a) Elastic modulus; (b) Initial horizontal stress coefficient; (c) Cohesion; (d) Internal
friction angle.
absolute displacements, as shown in Table 7.1. Two stations located within close
proximity are chosen for the tunnel convergence measurements; however, for the
application of the EBM, the two stations are combined by endowing each section
with time steps 1 and 2.

Selection of model parameters
The zone in which the ground shows plastic deformation due to tunnel
excavation is assessed by comparing the stress obtained from the elastic finite
element calculation and the strength obtained from the Hoek-Brown model. As
shown in Figure 7.13, the ground motion is almost elastic except at the invert
corner zones. Therefore, elastic analysis appears appropriate for this site.
Since the residual soil of granite origin is mostly cohesionless, it is almost
impossible to obtain undisturbed samples with typical sampling techniques. The