Page 229 - Numerical Analysis and Modelling in Geomechanics

210 I.-M.LEE AND D.-H.KIM
ratios of the tunnel deformation ahead of the face to the absolute deformation are
shown in Table 7.1. In summary, the unbiased (absolute) displacement is
estimated by using Table 7.1 for u and by using an extrapolation technique for u . i
o
Table 7.1 Ratio of the deformation ahead of the tunnel face to the absolute deformation

Figure 7.3 Characteristic line of deformation.

Evaluation of the proposed scheme

Data preparation
A comprehensive evaluation of the proposed feedback system was carried out
for the elasto-plastic case in a hypothetical site. The geological condition of the
site is presented in Figure 7.4, and the tunnel is assumed to be located in the
residual soil layer. The typical cross-section of the tunnel is a horseshoe shape
having a diameter of 10 m, and the primary support system consisting of 10 cm
thick soft shotcrete. Typical values of the geotechnical parameters are considered
as the initial estimated geotechnical parameters (prior information) for this case.
Since the site is hypothetical, the observed data are calculated using the finite
difference method code, FLAC-2D. The measurement points and displacements
are summarized in Figure 7.5 and Table 7.2.