Simulation Model for Tunnel Construction Costs

A computer-based Tunnel Cost Model has been developed. The model includes three submodels: a geologic submodel, a construction submodel, and a tunnel simulator. The geologic model uses the available geologic information expressed in terms of subjective probabilities to generate the likelihood of occurrence of various geologic conditions at defined locations in the tunnel. The construction submodel simulates cycles of construction operations under the various possible geologic conditions to assess the impact of these operations on time and cost. The tunnel simulator brings together the information produced by the two other submodels to simulate cycles of construction operations in many possible geologic profiles. Results of these simulations are time/cost distributions reflecting the uncertainty inherent in the estimate. An example problem of a 12,000-ft tunnel in shale/limestone geology is presented. Results indicate a range of total direct cost of −7,500,000−10,500,000, and a time of 210 days to 305 days. These ranges provide a quantitative indication of the uncertainty inherent in a final tunnel time and cost estimate.