Risk Analysis of Shield Construction by Polymorphic Bayesian Networks Model

Abstract:

Subway tunnel is characteristic of large-scale investment, many risk factors, large social impact, etc., which determines the need of risk management during the construction. As the fuzziness of risk, it is difficult to use an accurate probability or a probability interval to describe risks. So this paper suggests that shield excavation risks be analyzed by multiple probability intervals. Based on the five probability intervals which divide risk probabilities into five ranks in the subway and underground engineering, risk factor questionnaire has been designed, and the probability distributions of probability ranks about shield construction risk factors could be figured out through expert survey method. According to the questionnaire, Bayesian Networks is applied to establish a multi-state system to analyze the probability distributions. The multi-state system is used in the risk assessment of a subway tunnel, the probability rank of the project is figured out and at the corresponding probability rank，such risk factors as poor seal in the portals, axis deviation which causes segment failure and the damage, destruction of sealing material are considered as the key control objects.