Tunnels are a vital link in transport networks which represent a significant investment in all life cycle phases from planning, investigation works, construction and operation. Decisions through the whole life cycle of a tunnel should be based on solid facts and reliable data especially in the context of considerable impacts on both the environment and society. The calculation of total life time costs for different design alternatives, maintenance options and societal impacts can be used to compare different technical solutions and select the optimal design and maintenance alternative.
Generally problems related to tunnel degradation can be divided into those caused by external pressure and those caused by the deterioration of materials. These problems are gradually increased through all life cycle stages of a concrete structure such as a tunnel, therefore decisions about the timing and the type of maintenance should be based on degradation prediction models and monitoring of the structure performance or degradation processes. Uncertainties in the decision making process can be decreased by using information from monitoring which are used to establish triggering thresholds for the structure passing certain performance levels. In this paper the use of monitored tunnel deformations in a life cycle management model for a tunnel is presented. The monitoring data gives information about tunnel long term deformations that are used in the decision making process, in order to prevent occurrence of tunnel damage and consequently large maintenance costs.

tunnels, maintenance, life cycle management model, decision making