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One of the important steps in designing and implementation of tunneling projects is analyzing and managing the risks from the viewpoint of geotechnical risks. Second part of the Emamzadeh Hashem tunnel is one of the greatest civil projects in Iran that has faced with serious and important challenges in design because of the poor geological structure and geotechnical condition in excavation track. In this research, try to be after the geological studying in the tunnel excavation track, the overall risk amount be assessed by fault tree analysis. During this study, 4 important event including damage to the personnel, damage to the TBM, damage to the restraint system and deflection from the excavation track was identified and studied by using the geotechnical hazards like: encounter to fault and comminuted areas, squeezing, water inrush and tunnel instability. Results of the analysis show that reasons of the higher risk in this project are damage to the TBM and damage to restraint system. So, the higher risk should be reduced by doing some reducer proceedings like concrete injection. After these proceedings, the overall risk came to the poor area in the risk classification. According to the results, in this project, damage to the TBM and damage to restraint system have the highest risks and their risks should be reduced by doing some reducer proceedings like concrete injection. After these proceedings, the overall risk came to the poor area in the risk classification.

Introduction: The safety of CNG stations is important because of their location in urban areas, as well as to prevent accidents and to protect the safety of personnel, property, and environment. An event occurrence analysis with probability updating is the key to dynamic safety analysis. Methods and materials: In this study, the Failure Modes and Effects Analysis (FMEA) technique was used to determine the hazards of the study unit, the method of analyzing. After determining the hazards with high risk, the Bayesian fault tree analysis (BFTA) method was used to determine the effective causes of events occurrence and the type of possible relationships among them. Results: First, the phase of hazards identification, 16 Hazardous equipment were identified. Then the Risk Priority Number for the identified equipment was calculated. The results showed that the dispenser system had the highest risk priority number and was identified as the most critical equipment. According to this, the dispenser gas leakage (as the top event) was selected in this study. Then, the analysis of the dispenser gas leakage, using BFTA method identified 56 main causes, including 17 intermediate events and 39 basic events. Finally, cracking and corrosion of the dispenser hose were determined the most effective factor in the occurrence of the top event. The probability of occurrence of the top event based on FTA and BFTA analysis was calculated 9.67×10-2 and 9.11 × 10-2, respectively. Conclusion: The result of the study that by employing the Bayesian Network, can create a useful guideline to determine the relationship between the occurrence causes of the top event. This provides an assessment of the effectiveness of preventive measures before using them.

Introduction: Occupational accidents are of the main issues in industries. It is necessary to identify the main root causes of accidents for their control. Several models have been proposed for determining the accidents root causes. FTA is one of the most widely used models which could graphically establish the root causes of accidents. The non-linear function is one of the main challenges in FTA compliance and in order to obtain the exact number, the meta-heuristic algorithms can be used. Material and Method: The present research was done in power plant industries in construction phase. In this study, a pattern for the analysis of human error in work-related accidents was provided by combination of neural network algorithms and FTA analytical model. Finally, using this pattern, the potential rate of all causes was determined. Result: The results showed that training, age, and non-compliance with safety principals in the workplace were the most important factors influencing human error in the occupational accident. Conclusion: According to the obtained results, it can be concluded that human errors can be greatly reduced by training, right choice of workers with regard to the type of occupations, and provision of appropriate safety conditions in the work place.

Background and a ims: Subway system including infrastructure systems in the transportation industry can potentially exposed to fire, flood, earthquake and similar events and could create catastrophic losses to society. Therefore, this study aims to assess the risk of fire in Tehran subway stations (line 1). Methods: Inperforming this research, after the identifying the fire hazard resources in subway stations through observing, interviewing techniques and reviewing the documents, using fault tree analysis the causes of electrical fires in rectifier substations in line 1 of Tehran metro, was determined.Furthermore, with quantitative fault tree analysis, the probability of the fire risk was calculated per year. Results: Our findings indicate that, main causes of electrical fires in this post are including signs and devices, improper maintenance, improper implementation during equipment installation, inappropriate quality of equipment and their aging. The probability of accidents was calculated as one accident per every 11 years. Conclusion: Byholding training courses for personnel involved and careful monitoring during maintenance and installation of equipment, much lower probability risk would occur.

Recognition of any type of failures in systems and prediction of its reliability have important role in improvement of design of systems. Fault Tree Analysis (FTA) is one of the best techniques in analysis and improvement of complex systems. In this paper first, we show reliability block diagram (RBD) of Rocket Engine and then its fault tree is analyzed. Finally based on FTA, reliability of combustion of rocket engine is calculated.