Abstract
Comparison of calculated failure probabilities of technical systems with observed failure frequencies is an important part of the assessment of probabilistic calculations and can point to significant factors that are neglected in the calculations. Recent comparisons of failure probabilities and failure frequencies of nuclear power plants, bridges, and dams have shown that the calculated and observed values correspond surprisingly well. In addition, although various factors could be identified which have both positive and negative influences on the observed values, they almost cancel each other out. This study focuses on the comparison as it relates to tunnels. Extensive statistics indicate that most tunnel collapses occur during construction. Although this is also seen to a certain extent in bridges, it is not to the extent seen in tunnels. Events such as earthquakes and floods, which are the major causes of collapse of other structures, account for only about 10% to 20% of all tunnel collapses. Increasingly, tunnels are also being proven probabilistically. Based on these calculations, the available failure statistics can be compared with representative probabilistic tunnel proofs. The comparison shows large deviations between individual computations as well as between the mean value of all computations and the observed collapse frequencies.
Highlights
Probabilistic methods have been established for several decades in various engineering disciplines
Data per tunnel and per tunnel length corresponding to the observed collapse frequencies have been distinguished
The available probabilistic studies show a considerable variability, sometimes by up to six orders of magnitude. This variability can be interpreted as a very large uncertainty in the probabilistic calculations. This uncertainty may be a direct result of the large influence of input variables with a large uncertainty
Summary
Probabilistic methods have been established for several decades in various engineering disciplines. They are used, for example, in the design of aircrafts, spacecrafts, ships, and civil engineering structures (Spaethe 1992). Some publications (Kauermann and Küchenhoff 2011; Raju 2016) assume that the results of the probabilistic safety analysis in terms of core damage frequencies are systematically too low and do not fit with observed frequencies.
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Schedule a callMore From: ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering
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