Tunnel construction is a challenging project. Different concepts can be used to construct tunnels, such as cut and cover, NATM and mechanical method. In the construction phase of a tunnel project, tunnelling activities are: excavation, mucking, transportation, initial ground support, lining, and groundwater control. Selecting a suitable construction system for tunnels is not easy. The difficulty stems from the large number of parameters that control the selection of construction methods. For example; excavation can be done by excavators, drill and blast, roadheader, and TBMs. Selecting the proper excavation method depends on technical and non-technical factors. Technical factors are, for instance, ground conditions, tunnel depth, length, shape, and cross sectional area. Non-technical factors include cost, time, and public and political factors. Selection of the most efficient construction methods results in a reduction of project cost, time and hazards.
In this research, a computer model is developed to help the decision maker in selecting an efficient tunnelling system in the preliminary stage of the project. Controlling factors that can affect the selection of construction methods were determined. The model of this research was developed based on the opinions of tunnel experts about efficiency of construction methods for different controlling factors.
The model has two phases, in the first phase, it calculates the efficiency percentages of construction methods of each tunnelling activity, such as excavation, supporting and lining, and it gives a report about construction methods of each activity. In the second phase, the model combines construction methods of all activities to determine the possible alternative tunnelling systems.