assessment of optimal tunnel boring machine (tbm) excavation method by analyzing stability of tunnels in squeezing rock conditions (case study: chamshir tunnel)

The implementation of infrastructure projects, such as tunnels, in the transportation industry is always considered one of the most expensive projects for the development of countries. one of the important issues in tunneling is the behavior that the earth exhibits in the squeezing condition. in the squeezing ground, the stones move into the tunnel and cause problems in the support and continuation of the tunnel construction. for tunneling in squeezing rock, firstly, it is necessary to know the type of phenomenon and its intensity carefully, and then design the required excavation method and support system according to the available information. in this article, it has been tried to identify the squeezing ground around tunnel and its behavior by numerical analysis. as an example, chamshir tunnel has been modeled for this purpose. according to the conditions of the tunnel boring machine in squeezing rock, some issues like instability of the tunnel walls, the relative flexibility of the machine in changing the excavation diameter, the supply of propulsion forces and the machine extension control, the most suitable mechanized excavation equipment should be selected and its driving force should be determined in such a way as to prevent the tbm from getting stuck inside the tunnel.