ABSTRACT
High convergences developed between chainage 1200 to 1550 m, with the DSM section applied systematically following chainage 1400 m. The special monitoring section at chainage 1443 m is taken as representative. Figure 4 shows the displacement distribution given by the multi-position borehole extensometer along direction 4 (right side) versus time and the mobilized zone around the tunnel where the radial strain is greater than 1%, a strain limit taken as the onset of squeezing behavior. It is of interest to observe that the zone around the tunnel with strains greater than this value is non symmetrically distributed, ranging in extent from 10-11 m maximum (right) to 1-2 m minimum (left).
