Licentiate seminar – Mohammad Mohammadi

Mohammadi, M. (2021) Probabilistic time estimation in tunnel projects. Licentiate thesis. TRITA-ABE-DLT; 213: Stockholm: KTH Royal Institute of Technology.

urn:nbn:se:kth:diva-304245

Abstract: Transport infrastructure projects, including tunneling, suffer from time delays and cost overrun. A literature review shows that the effect of uncertainty has been neglected in explaining time and cost overrun meaning that technical explanations matter. Probabilistic estimations of time and cost can be employed for dealing with uncertainty in transport infrastructure projects. In this licentiate thesis, KTH’s probabilistic time and cost estimation model for tunneling projects (Isaksson and Stille, 2005, Rock Mech. Rock Eng., 38, 373-398) was improved. The improvements include breaking down the production activities into their sub-activities, which form the basis for assessing times (or costs) for tunnel construction. In addition, the exceptional time and the length of model’s geotechnical zones are described as stochastic variables instead of deterministic values used in the original model. Given its hierarchical structure, the model can be used for time and cost estimation of all types of tunnels and all construction methods in various geological condition. The improved version of the model uses three types of input parameters that are probabilities of occurrences of different geological condition and identified undesirable events, production effort of sub-activities (i.e. time spent for performing the sub-activity per unit length of tunnel) and additive delay time that is imposed as a result of occurrence of undesirable events. The important issues in modeling the uncertainty in the production efforts of sub-activities are also explained.