In-situ measurement of rock deformation was carried out at Hiraki Mine. Two extensometers were installed from an opening which was excavated 30 meters above an experimental tunnel before the exavation and two set of extensometers were also installed around a periphery of the tunnel. Displacement of rock around the tunnel was measured before, during and after the excavation of the tunnel. It became clear that the rock around the tunnel was deformed elastically, but asymmetrically.
The change of rock deformation around an opening with the advance of face was calculated using a three dimensional finite element method under three different stress conditions. Then we discussed the possibility to introduce two dimensional finite element analysis to evaluate three dimensional problem. The inner pressure was applied at the periphery of an opening, then was reduced with the advancement of a face. Results showed that we can practically use a two dimensional finite element method with a sufficient accuracy.
This technique was applied to evaluate the deformation of the experimental tunnel at Hiraki Mine. It was found that (1) rock deformation can be calculated by elastic analysis except the area close to the surface of the tunnel where rock damaged by blasting, and (2) asymmetrical deformation around the tunnel was occurred mainly because of the inhomogeneity of rock mass.
