The construction industry has one of the highest work accident rates in the world when compared to other industrial undertakings, particularly tunneling construction. Risk events are often interrelated. The occurrence of a technical risk usually carries a cost and scheduled consequences. Schedule risks typically impact cost escalation and project overhead. Some projects are primarily schedule-driven; other projects are primarily cost or quality-driven.
The objective of this study is to perform a comprehensive investigation about hazards and risks in the construction process of tunnels by carrying out a state-of-the-art study on the most critical risks in tunnel construction projects. The methodology used was a systematic review of all available literature in the previous studies. As a result of the review, a six-group risk categorization was developed, which includes risks associated with confined spaces, ventilation & air monitoring, fires, physical & chemical hazards, electricity, personnel safety & emergency plans. According to the output of this study, managing hazards and risks will aid managers and engineers in attaining their goals, achieving safety management, reducing, and controlling accidents and injuries in tunnel construction sites. This will result in a safer workplace, more worker awareness, and a reduction in project schedules and costs.