The probabilistic time and cost risk analysis of a challenging part of an urban tunneling project

• Risk analysis of the construction time and cost in an urban tunneling project.
• Consideration of different scenarios of subsidence control measures.
• Utilization of the Markov model to generate ground classes.
• Helping make the best decisions in a highly uncertain geological environment.

A predominant characteristic of geotechnical works and more particularly tunneling projects, is the uncertainty that surrounds the geologic medium in which the construction is to be performed. This paper is dealing with the risk analysis of both the construction time and cost of a challenging part of Tehran Metro Line 7, an urban tunneling project which is currently being under development. The Decision Aids for Tunneling (DAT) has been utilized for this assessment, concerning the risk analysis by taking into account different scenarios relating to the measures implemented to prevent surface subsidence problems. The results have shown that selection of different sorts of methods will help control the risk of escalating the project’s total construction cost and time to completion. This research delivers useful information to concurrently help the owner, the contractor as well as the designer of the project in making the most appropriate decisions under such a highly uncertain and challenging geological environment.