ABSTRACT
The crossing of fault zones by underground works is often coupled with serious technical problems for tunnel boring machines. Fault zones may sometimes act as highly conductive groundwater channels or natural flow barriers. Such barriers can develop very-high water pressure behind or inside them. Crossing through them, especially with deep galleries, there is a considerable risk of meeting a sudden flow of water and crushed rock material under high pressure. Squeezing problem and collapse of tunnel surrounding rocks may also cause long delays in tunnel advance due to jamming of shield or cutterhead. So, to avoid difficulties in tunneling projects, it is very important to identify the main characteristics of fault zones and predict material behavior in such complex zones before crossing them by TBM. Knowledge gained from the application of TBM in different types of fault zones in various geological conditions can be utilized as a tool for predicting tunneling conditions in a given geological situation. In this paper, based on the experiences gained from mechanized tunneling in Iran and considering the most important influencing factors, a preliminary proposal for the classification of rock mass behavior and geological hazards in fault zones has been presented.
