Detailed probabilistic construction estimating by Monte Carlo simulation

Abstract

The complexity of construction operations and their associated uncertainties lead to a significant amount of risk in construction estimating. Conventional deterministic estimating cannot capture these uncertainties in a systematic and quantitative manner. Thus, a probabilistic approach is necessary to assess these risks. This paper presents a detailed probabilistic estimating using Monte Carlo simulation. The probabilistic estimating of a tunneling project is presented as an example application. Tunnel advance rates are estimated using detailed probabilistic scheduling of tunneling operations. Precedence activity networks for tunneling operations are constructed as functions of the chosen excavation and support method and the revealed geologic conditions (tunneling alternatives). The duration of tunneling activities is expressed by time-estimating equations, and their associated uncertainties are assessed by subjective assessment using the Perry & Greig method. Probabilistic scheduling is analyzed by Monte Carlo simulation performed in the ProbSched program. The results provide probability distributions of tunnel advance rates for all possible alternatives, which can be used to determine optimal excavation and support methods for the project.