Probabilistic Risk Assessment And Prediction Of Delay In Conventional Tunnelling

In this study, first of all, definitions of main term such as “risk”, “risk analysis”, “risk event”, “consequence” and “likelihoods” were made to avoid any confusions about these terms, and significance of risk analysis and management in engineering projects was emphasized. Then, both qualitative and quantitative risk analysis techniques were mentioned and within scope of the study, Severity Risk Analysis, Monte Carlo Simulation and Discrete Event Simulation methods were selected in order to analyze the risks regarding Conventional Drill and Blast tunnelling and their impacts on construction schedule. After all hazards that would be encountered during tunnel construction by Conventional Drill and Blast tunnelling had been identified, a preliminary risk analysis to sort out and prioritize ‘intolerable’ risks was conducted. When risk scores were taken into consideration, it was seen that ‘intolerable’ risks to schedule could be classified into five groups that are; accidents, labour disputes, defective work, delay of material delivery and plant and machinery failure. According to these five classified groups of risks, a correlation analysis using Decision Making Trial and Evaluation Laboratory and Schedule Delay Analyses using Monte Carlo and Discrete Event Simulation techniques was conducted. Finally, the results of the Schedule Delays predicted by the quantitative risk analysis techniques of Severity, Monte Carlo Simulation and Discrete Event Simulation were validated and interpreted together by making comparisons against actual durations from Awash-Kombolcha-Hera Gebeya Railway project by considering the Root Mean Square Error. The results showed that the Discrete Event Simulation model developed was a superior method of predicting tunnelling delay followed Monte Carlo Simulation and lastly Severity Analysis respectively.

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