Probable Hazards on Urban Tunnels during Design and Construction

Nowadays, the existence of limitation in urban spaces, the requisiteness of consideration to land use from the environmental and social perspective, as well as the necessity to develop the urban transportation network, has forced those involved in urban management of cities to use underground spaces as one of the best alternatives. The usage of these infrastructures in developed countries, has led to the very well results on reducing the traffic and urban transportation issues, which unavoidably necessitates their application. On the other hand, the potential of the occurrence of hazards and incoming risks on tunnels has always been considered as the main challenge of tunneling in each three phases of design, construction, and operation, and with regard to the remarkable costs related to construction and operation of these establishments, the identification of these hazards and investigation of their impacts on tunnels has a particular importance on reducing the probable damages. In phases of design and construction, the investigation of types of hazards on urban tunnels shows that hazards such as the occurrence of mistakes in planning stage such as preparation of technical specifications and estimation of design parameters; computational and numerical mistakes; managerial and controlling mistakes; the occurrence of errors and mistakes during the construction phase of tunnel; hazards due to unknown situations of underground spaces; the existence of underground water; entrance of water and flood; effects of earthquake on tunnel; and hazards due to subsidence as well as the gases must be considered in the risk management and securing the safety of urban tunnels.