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212 I.-M.LEE AND D.-H.KIM
Figure 7.5 Location of measurement points.
friction angle will be major influencing factors on ground motion. It has also
been concluded that the ground motion is insignificantly affected by cohesion.
Parameter estimation
As shown in Figure 7.5, plastic deformation occurs around the tunnel. Therefore,
four parameters must be estimated: the cohesion, the internal friction angle, the
elastic modulus, and the initial horizontal stress coefficient. Since the tunnel
crown is located within the residual soil layer, only the parameters for the
residual soil layer are assessed. The coefficient of variation of model parameters
is assumed to be 0.3 considering that large uncertainties are encountered.
In order to check the effect of the number of measurement points in the
feedback system, they are varied during the analysis. The results of the analysis
are listed in Table 7.3 and the prior estimates are also tabulated for comparison.
Table 7.3 shows that at least six measurement points must be installed to obtain a
reliable estimation.
Case study
The application of the proposed method is extended to a subway tunnel in Pusan,
Korea, to illustrate the applicability of the EBM beyond parameter estimation.
Applications in this chapter concentrate on the following. First, in order to