Page 231 - Numerical Analysis and Modelling in Geomechanics
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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
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