In this thesis we discussed the matrix method for the cost estimate in tunnel construction, which is defined in ÖNORM B 2203-1. In the first part of the thesis we described the course of geomechanical tunnel design, which includes a matrix method. We particularly highlighted the advantages of the matrix method over the previous system, which was used in Slovenia until 2007. In the second part of the thesis, we used a hypothetical 500-meter-long section of a tunnel to show the application of the matrix system. To see the advantages of the method, we used two payment models. The first payment model strictly followed the matrix method, while the other model divided the time-dependent costs into the cost of the excavation. Cost estimate for the tunnel section was made for three different case events (A, B and C). In the case A the geotechnical conditions matched our predictions, whereas in cases B and C occurred some variations. The geotechnical conditions in case B were more favorable than those in tender documents, and the conditions in case C were more complex. From the results obtained, we observed that the total costs of the tunnel section were the same for both payment models. In cases B and C payment model 1 contained greater deviations from the predicted costs than payment model 2. We determined that the differences between payment models caused by the geotechnical conditions increase with growth of time-dependent cost of the site and are strongly dependent on the tunneling time.
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