| With the global warming and a large amount of sea ice melting,the available Arctic Sea Route has greatly enhanced the value of Arctic shipping.Ship operations under icebreaker assistance have become an essential way to facilitate the safe navigation of merchant vessels sailing through the Arctic Sea Route in ice-covered waters,but they can also put the crew and the ship in danger caused by a possible collision between the assisted ship and the icebreaker.However,due to the complicated and volatile navigation environment in Arctic ice regions,frequent ship collision accidents occur between icebreaker and the escorted ship,and statistics for collision accidents in Arctic ice-covered waters indicate that the collision frequency of ships under the icebreaker assistance has been the highest.In view of the typical ship operation mode in Arctic ice-covered waters,it is of great significance to analyze ship collision risk and anti-collision decision making methodology for ship escort operations.Ship collision risk contributing factors identification,collision risk analysis modeling and traffic simulation are used to analyze the risk factors of ship collision under icebreaker assistance.Ship collision risk analysis and anti-collision decision making of ships during escort operation are carried out.Meanwhile,the ship collision risk analysis and the collision avoidance decision under icebreaker assistance are fulfilled.The main contents of the research are shown as follows:(1)Identification of collision risk contributing factors for icebreaker assistance in ice-covered waters.Based on the statistical analysis of the ship collision accidents during escort operation,this paper analyses the risk contributing factors of ship collision and a hierarchical model of risk contributing factors of ship collision is established under the protection of icebreaker in terms of external factors,organizational factors,unsafe supervision,preconditions of unsafe acts and unsafe acts.Furthermore,the frequency of identified collision risk contributing factors is statistically analyzed to identify the risk factors of ship collision between icebreaker and the assisted ship.(2)Ship collision risk analysis of icebreaker assistance in ice-covered waters.A Fault Tree Analysis(FTA)model is utilized to analyze the fundamental collision risk factors according to a statistical analysis of accident reports and expert judgments based on a HFACS-SIBCI model.The structural importance of the risk factors in the escort operation is calculated,and the minimum cut set is listed.Combined with the minimum cut sets and the structural importance of collision risk factors,a qualitative analysis is carried out to analyze collision risk factors under icebreaker assistance,where Risk Control Options(RCOs)are formulated.An important guidance for the risk control of ship collisions during icebreaker assistance in ice-covered waters is provided for lawmakers and shipping companies.(3)Study on anti-collision decision making methodology for ship escort operations.With focus on escort operations under icebreaker assistance in Arctic ice-covered waters.Firstly,ship navigation is simulated under different ice conditions,and the speed of ship sailing is predicted under different navigation conditions according to the characteristics of ship movement.A method for collision situation assessment of the ships in team of time dimension and space dimension is proposed combined with an analysis of the collision situation between ships and the maneuverability of ships.An feasible collision avoidance strategy is proposed based on the acceptable probability of ship collision risk as the risk threshold.Finally,A case study is carried out to assess the timing of collision avoidance of ships in different navigation situations.The results show that the model can accurately calculate the safety distance between “YONG SHENG” and “50 LET POBEDY”,which can provide theoretical guidance for anti-collision decision making methodology for ship escort operations. |
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