The stability analysis of rock mass surrounding the inlet section of Gardaneh Rokh tunnel using empirical and numerical method, Shahrekord-Esfahan Highway

Abstract

The Gardaneh Rokh tunnel is being excavated with the length of 1300m it axis striking of N28. The height of tunnel section is 8.6m and its width is 13m. To characteristics of the discontinuities were recorded from 5 outcrops as survey stations. A series of laboratory tests was conducted on the intact rock samples selected from cores taken from two boreholes to get the physical and geomechanical properties. The rock mass along the tunnel enroute was divided into 5 structural zones and were then classified based on the Q and RMR systems. The required support systems were also determined according to the systems. Regarding tunnel stability analysis, the tunnel inlet section as the weakest zone of rock mass located in km 6+300 (structural zone 5) is numerically modelled and analyzed using PLAXIS software with and without support system. The excavation and support installation process was modelled in 3 phases. The results of the numerical modelling show that the crown and sidewalls instabilities are mainly reduced by installation of partial shotcrete support in crown and sidewalls. However, the support installation even in lower sidewalls may not substantially reduce the displacements in invert.