Management Criterion for Large Deformation Tunnels

The limit displacement was calculated with regard to a large deflection tunnel. The continuum calculation model was established with actual parameters of the surrounding rock of the tunnel as input. In the simulation calculation, the action occasion of the support structure was determined based on the ratio of the measured rock pressure to the geo-stress, and the bearing capacity of the R.C. compressive bending component of the support was expressed with the axial force and bending moment on losing capacity of the support structure in loading; The limit displacement of the tunnel wais determined finally combined with the measured displacement of control points on collapsed or gauge-intrusive sections and cracked primary support or secondary lining sections. Since the deforming rate is more concerned than the displacement in drill and blast tunnel construction, three-level-management of deflection and deforming rate was proposed based on the statistical analysis of measured deforming rate, and the safety requirement for deflection control in construction. The management criterion has reference value to other similar tunnels where difficulty is encountered due to large deflection occurring in construction.