Modeling uncertainty in the New York City no. 7 subway line extension project using Decision Aids for Tunnelling (DAT)

Abstract

Given the frequent cost overruns and schedule delays associated with underground construction projects, it is imperative that a detailed estimate of both be developed and considered prior to starting construction. The Decision Aids for Tunnelling (DAT) allow engineers to consider the uncertainties associated with project ground conditions, construction activities, and problem events, and to determine distributions of total cost and time for completion of construction. This is done by simulating the geological conditions in each DAT simulation and then using the resulting conditions in further simulations of construction processes. As each simulation will only produce one resulting point with a value for cost and a value for time, numerous simulations must be run by the DAT in order to produce a complete scatter gram with a distribution of total possible costs and duration. This thesis utilizes the DAT to develop a distribution for the total cost and duration of constructing the New York City Number 7 Subway Line Extension Project's Running Tunnels using a tunnel boring machine. The results will show the applicability of the DAT, given pre-construction geologic information and post-construction TBM progress data but only total cost. As is to be expected, subsurface conditions were limited to pre-construction baseline information. Despite these limitations, use of available data by the DAT generated a scattergram, forecasting a range of possible cost and duration outcomes.